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Plantar fasciitis is a frequently occurring overuse injury of the foot. Shoes with a stiff rocker profile are a commonly prescribed treatment modality used to alleviate complaints associated with plantar fasciitis. In rocker shoes the apex position was moved proximally as compared to normal shoes, limiting the progression of the ground reaction forces (GRF) and peak plantarflexion moments during gait. A stiff sole minimizes dorsiflexion of the toes. The aim of this study was to investigate whether the biomechanical effects of rocker shoes lead to minimization of plantar aponeurosis (PA) strain during gait in patients with plantar fasciitis and in healthy young adults. 8 patients with plantar fasciitis (1 male, 7 females; mean age 55.0 ± 8.4 years) and 8 healthy young adults (8 females; mean age 24.1 ± 1.6 years) participated in the study. Each participant walked for 1 minute on an instrumented treadmill while wearing consecutively in random order shoes with a normal apex position (61.2 ± 2.8% apex) with flexible insole (FN), normal apex position with stiff insole (SN), proximal apex position (56.1 ± 2.6% apex) with flexible insole (FR) and proximal apex position with stiff insole (SR). Marker position data of the foot and lower leg and GRF were recorded. An OpenSim foot model was used to compute the change in PA length based on changes in foot segment positions during gait. The changes in PA length due to increases in Achilles tendon forces were computed based on previous data of a cadaver study. PA strain computed from both methods was not statistically different between shoe conditions. Peak Achilles tendon force, peak first metatarsophalangeal (MTP1) joint angle and peak plantarflexion moment were significantly lower when walking with the rocker shoe with a proximal apex position and a stiff insole for all subjects (p<.05). Changes in Achilles tendon forces during gait accounted for 65 ± 2% of the total PA strain. Rocker shoes with a stiff insole reduce peak dorsiflexion angles of the toes and plantar flexion moments, but not PA strain because the effects of a proximal apex position and stiff insole do not occur at the same time, but independently affect PA strain at 80–90% and 90–100% of the stance phase. Rocker shoes with an apex position of ~56% are insufficient to significantly reduce peak PA strain values in patients with plantar fasciitis and healthy young adults. [ABSTRACT FROM AUTHOR]

When we perform a movement we generally have a clear distinction between which parts of the world constitute our body and which parts do not. However, how the sense of ownership over our body supports movement is not yet fully understood. We aimed to see whether a sense of ownership over the hand supports the performance of rapid hand movements. In three experiments (n = 48, n = 30, n = 24), we presented participants with congruent and incongruent visuotactile and visuoproprioceptive information regarding their own hand. In keeping with previous experiments, multisensory disintegration resulted in a reduction in the subjective sensation of ownership over the hand, as reflected in questionnaire responses. Following sensory stimulation, participants were required to rapidly abduct their index finger whilst the movement was tracked. We examined the hypothesis that, should a sense of ownership over the limb be necessary for generating rapid movements with that limb, reaction time would increase when hand ownership was reduced, whilst the acceleration and velocity of the movement would decrease. We observed that reductions in own hand ownership did not interfere with rapid index finger abduction, suggesting that the motor system may not be reliant on a subjective sense of ownership over the body in order to generate movement. [ABSTRACT FROM AUTHOR]

Sport fencing is an open-skilled combat sport practiced around the world. Although previous research addressed kinematics of the lunge and fleche, there are currently no studies on the flick. The flick is a high-level action that involves bending the blade toward the opponent, much like a whip or fly-fishing cast. The aim of our research was to identify the kinematic variables that significantly influence scoring success in two elite foil fencers. In particular, we asked what aspect of the movement each individual fencer can change to improve their likelihood of scoring. Two elite foil fencers of similar skill were instructed to execute flicks at a dummy target that mimicked the opponent’s shoulder. High speed video (650 fps) captured the motion of the tip of the foil, blade of the foil, and limb joints; the latter were used to calculate joint angular velocities, hand height and distance throughout the flick. Scoring success was determined with a conventional scoring box. Our results showed that the two fencers exhibited significantly different kinematics, coordination and scoring. Using three complementary regression approaches, we showed that each fencer could improve scoring by changing specific aspects of their kinematics. For fencer A, only improvement in consistency in distance from the target would improve scoring. For fencer B, the changes were more complex. In addition to improvement in consistency in distance, fencer B could also increase (finger, wrist) or decrease (shoulder) joint angular velocity or improve consistency of limb joint angular velocities. Unexpectedly, and in contrast to common coaching practice, hand height had only a weak effect, possibly because both fencers had learnt to keep their hand high at the end of the action. In summary, our results emphasize that coaching of elite fencers should be individualized. [ABSTRACT FROM AUTHOR]

Inverse dynamics problems are usually solved in the analysis of human gait to obtain reaction forces and moments at the joints. However, these actions are not the actual forces and moments supported by the joint structure, because they do not consider the forces of the muscles acting across the joint. Therefore, to analyse bone-on bone forces it is necessary to estimate those muscle forces. Usually, this problem is addressed by means of optimization algorithms. One of the parameters required to solve this problem is the musculotendon geometry. These data are usually taken from cadavers or MRI data from several subjects, different from the analysed subject. Then, the model is scaled to the subject morphology. This procedure constitutes a source of error. The goals of this work were two. First, to perform a sensitivity analysis of the influence of muscle insertion locations on the muscle forces acting on the hip joint and on the hip joint bone-on-bone forces. Second, to compare the hip joint bone-on-bone forces during gait cycle obtained through muscle insertion locations taken from a musculoskeletal model template and a scaling procedure to those obtained from a subject-specific model using an MRI of the subject. The problem was solved using OpenSim. Results showed that anatomical variability should be analysed from two perspectives. One the one hand, throughout the gait cycle, in a global way. On the other hand, at a characteristic instant of the gait cycle. Variations of ±1 cm in the position of the attachment points of certain muscles caused variations of up to 14.21% in averaged deviation of the muscle forces and 58.96% in the peak force in the modified muscle and variations up to 57.23% in the averaged deviation of the muscle force and up to 117.23% in the peak force in the rest of muscles. Then, the influence of that variability on muscle activity patterns and hip bone-on-bone forces could be described more precisely. A biomechanical analysis of a subject-specific musculoskeletal model was carried out. Using MRI data, variations up to 5 cm in the location of the insertion points were introduced. These modifications showed significant differences between the baseline model and the customized model: within the range [-12%, 10%] for muscle forces and around 35% of body weight for hip bone-on-bone forces. [ABSTRACT FROM AUTHOR]

Little is known regarding how repetitive finger movement performance impacts other fine motor control tasks, such as circle drawing, in persons with Parkinson’s disease (PD). Previous research has shown that impairments in repetitive finger movements emerge at rates near to and above 2 Hz in most persons with PD. Thus, the purpose of this study was to compare circle drawing performance in persons with PD that demonstrate impairment in repetitive finger movement and those that do not. Twenty-two participants with PD and twelve healthy older adults completed the study. Only participants with PD completed the repetitive finger movement task. From the kinematic data for the repetitive finger movement task, participants were grouped into Hasteners and Non-Hasteners. Participants with PD and the healthy older adults completed a series of circle drawing tasks at two different target sizes (1 cm and 2 cm) and three pacing conditions (Self-paced, 1.25 Hz, and 2.5 Hz). Kinematic and electromyography data were recorded and compared between groups. Results revealed that, in general, persons with PD demonstrate impairments in circle drawing and associated electromyography activity compared to healthy older adults. Moreover, persons with PD that hasten during repetitive finger movements demonstrate significantly increased movement rate during circle drawing, while those persons with PD that do not hasten demonstrate a significant increase in width variability. This suggests that differing motor control mechanisms may play a role in the performance of fine motor tasks in persons with PD. Continued research is needed to better understand differences in circle drawing performance among persons with PD to inform future development of patient-centered treatments. [ABSTRACT FROM AUTHOR]

Following unpredictable large-magnitude stance perturbations diverse patterns of arm and leg movements are performed to recover balance stability. Stability of these compensatory movements could be properly estimated through qualitative evaluation. In the present study, we present a scale for evaluation of compensatory arm and leg movements (CALM) in response to unpredictable displacements of the support base in the mediolateral direction. We tested the CALM scale for intra- and inter-rater reliability, correlation with kinematics of arm and leg movement amplitudes, and sensitivity to mode (rotation, translation and combined) and magnitude (velocity) of support base displacements, and also to perturbation-based balance training. Results showed significant intra- and inter-rater coefficients of agreement, ranging from moderate (0.46–0.53) for inter-rater reliability in the arm and global scores, to very high (0.87–0.99) for inter-rater leg scores and all intra-rater scores. Analysis showed significant correlation values between scale scores and the respective movement amplitudes both for arm and leg movements. Assessment of sensitivity revealed that the scale discriminated the responses between perturbation modes, platform velocities, in addition to higher balance recovery stability as a result of perturbation-based balance training. As a conclusion, the CALM scale was shown to provide adequate integrative evaluation of compensatory arm and leg movements for balance recovery stability after challenging stance perturbations, with potential application in fall risk prediction. [ABSTRACT FROM AUTHOR]

This study investigated the influence of age and visual occlusion on fast reach-to-grasp movements. The effect of visual occlusion on reach-to-grasp movement was examined using a task that heavily relies on feed-forward control. Three groups of healthy adults aged 22, 49 and 65 on average performed fast reach-to-grasp movements with full visual and partial visual occlusion conditions of the hand during the initial part of movement. Regarding the effect of age, the all parameters of reach-to-grasp movement were deteriorated with age, except relative time to maximum velocity and spatial coordination. Regarding the effect of visual condition, participants reached with prolonged movement time, lower peak velocity, and later occurrences of peak velocity and peak aperture, as well as decrease in spatial coordination. Regarding the effect of age on visual condition, visual occlusion resulted in a longer movement time and delayed time to maximum velocity in middle-aged and older groups compared to full vision, but the difference was not observed in the younger groups. Conclusion: Reach-to-grasp performance deteriorated with age and the performance was affected when vision of the hand at initial movement was occluded. Overall, movement performance in middle-aged and older adults was affected by visual occlusion, whereas it was unaffected in younger adults. The results indicate that visual feedback of the hand at initial movement is important to control reach-to-grasp movement of middle-aged and older adults during real tasks. [ABSTRACT FROM AUTHOR]

Objective: The objective of the current study was to investigate the effect of four different crank fore-aft positions on elbow flexion and shoulder protraction, the consequent propulsion kinetics and the physiological responses during handcycling. Methods: Twelve able-bodied male participants volunteered in this study. Crank fore-aft positions were standardised at 94%, 97%, 100% and 103% of the participants’ arm length. Two submaximal 3 min trials were performed at a fixed cadence (70 rpm), in a recumbent handcyle attached to an ergometer at two fixed power outputs (30W and 60W). Elbow flexion, shoulder protraction, propulsion kinetics and physiological responses of the participants were continuously measured. Results: As crank fore-aft distance increased, a decrease in elbow flexion (42±4, 37±3, 33±3, 29±3°) and an increase shoulder protraction was observed (29±5, 31±5, 34±5, 36±5°). The percentage of work done in the pull phase increased as well (62±7, 65±7, 67±6, 69±8%, at 60W), which was in line with an increased peak torque during the pull phase (8.8±1.6, 9.0±1.4, 9.4±1.5, 9.7±1.4Nm, at 60W) and reduced peak torque during the push phase (6.0±0.9, 5.6±0.9,5.6±0.9, 5.4±1.0Nm, in 60W condition). Despite these changes in work distribution, there were no significant changes in gross mechanical efficiency (15.7±0.8, 16.2±1.1, 15.8±0.9, 15.6±1.0%, at 60W). The same patterns were observed in the 30W condition. Conclusions: From a biomechanical perspective the crank position closest to the trunk (94%) seems to be advantageous, because it evens the load over the push and pull phase, which reduces speed fluctuations, without causing an increase in whole body energy expenditure and hence a decrease of gross mechanical efficiency. These findings may help handcyclists to optimize their recumbent handcycle configuration. [ABSTRACT FROM AUTHOR]

This study aimed to measure muscle activity and motion kinematics during chair-based exercises under submerged and non-submerged conditions. Twelve healthy men performed chair-based standing and sitting movements. Surface electrodes were attached at the tibialis anterior, gastrocnemius, rectus femoris, biceps femoris, rectus abdominis, and erector spinae. The ankle, knee, and hip joint angles and forward inclination angle of the trunk segment in the sagittal plane were calculated. The mean muscle activities during both movements in the submerged condition for the entire motion were lower than those in the non-submerged condition except in the tibialis anterior and biceps femoris during the sitting movement (in the standing exercise, rectus femoris: 14.1% and 5.2%; and erector spinae: 18.3% and 13.6% in non-submerged and submerged conditions, respectively; and in the sitting exercise, rectus femoris: 12.1% and 4.5% and erector spinae: 12.9% and 9.9% in the non-submerged and submerged conditions, respectively). However, the integrated muscle activity in submerged conditions was similar or higher to that in non-submerged conditions during both movements, except for the rectus femoris. This was mainly due to the increased duration of motion (44.3% and 39.9% longer for standing and sitting exercises in submerged conditions, respectively, compared with non-submerged conditions). The hip joint flexion at the beginning and end of movement and forward inclination angles of the trunk segment at the beginning of the movement in the submerged condition were larger than those in the non-submerged condition during both movements (hip: 126.1° and 111.5° at the beginning, 182.3° and 178.4° at the end and trunk: 2.7° and 17.4° at the beginning in non-submerged and submerged conditions for the standing exercise, respectively; hip: 182.4° and 178.0° at the beginning, 125.9° and 111.1° at the end and trunk: 2.2° and 16.9° at the end in non-submerged and submerged conditions for the sitting exercise, respectively). Reduced or similar muscle activity but similar or higher muscular effort was observed in the submerged condition for all the muscles except the rectus femoris, with the upper body inclined forward. These findings could have beneficial implications for the prescription of exercise and rehabilitation regimens. [ABSTRACT FROM AUTHOR]

Objectives: To examine the short-term effects of selective dorsal rhizotomy (SDR) ± soft-tissue surgery on gait in cerebral palsy (CP) compared to matched controls with no surgical intervention. Methods: Participants had gait analysis before and one year after SDR. Non SDR participants were retrospectively matched for age and all significant gait parameters. The SDR group was further subdivided into those who had concomitant orthopaedic surgery and those who had SDR only. Results: The SDR group consisted of 29 participants (mean age 5.8 years at baseline, 7.7 years at follow-up). Of these, 13 had concomitant orthopaedic surgery. The non SDR group consisted of 18 participants (mean age at baseline 6.1 years, 8.1 years at follow-up). SDR ± soft-tissue surgery significantly improved step-lengths, knee flexion at initial contact and mid-stance, ankle dorsiflexion, foot progression and timing of peak knee flexion. None of these improvements in gait were seen without surgical intervention. While more improvements were seen in those who had SDR and orthopaedic surgery, SDR only resulted in improved step-lengths, knee extension, foot progression and timing of peak knee flexion. Conclusions: SDR ± soft-tissue surgery results in short-term improvements in gait which are not seen without surgical intervention. While those who had SDR and soft-tissue surgery demonstrated more changes in gait, many improvements were attributable to SDR only. [ABSTRACT FROM AUTHOR]

The robustness of motor outputs to muscle dysfunction has been investigated using musculoskeletal modeling, but with conflicting results owing to differences in model complexity and motor tasks. Our objective was to systematically study how the number of kinematic degrees of freedom, and the number of independent muscle actuators alter the robustness of motor output to muscle dysfunction. We took a detailed musculoskeletal model of the human leg and systematically varied the model complexity to create six models with either 3 or 7 kinematic degrees of freedom and either 14, 26, or 43 muscle actuators. We tested the redundancy of each model by quantifying the reduction in sagittal plane feasible force set area when a single muscle was removed. The robustness of feasible force set area to the loss of any single muscle, i.e. general single muscle loss increased with the number of independent muscles and decreased with the number of kinematic degrees of freedom, with the robust area varying from 1% and 52% of the intact feasible force set area. The maximum sensitivity of the feasible force set to the loss of any single muscle varied from 75% to 26% of the intact feasible force set area as the number of muscles increased. Additionally, the ranges of feasible muscle activation for maximum force production were largely unconstrained in many cases, indicating ample musculoskeletal redundancy even for maximal forces. We propose that ratio of muscles to kinematic degrees of freedom can be used as a rule of thumb for estimating musculoskeletal redundancy in both simulated and real biomechanical systems. [ABSTRACT FROM AUTHOR]

Background: This study aimed to investigate the effects of walking speed and slope on foot pressure changes in young healthy adults. Methods: Twenty young healthy adults (mean age 22.4 years, SD 1.2 years; 10 male and 10 female) participated in the study. Dynamic pedobarographic data during treadmill walking were obtained for combinations of three different walking speeds (3.2 km/hr, 4.3 km/hr, and 5.4 km/hr) and 5 different slopes (downhill 8 degrees, downhill 4 degrees, ground walking (0 degree), uphill 4 degrees, and uphill 8 degrees). Pedobarographic data such as the peak pressure and pressure–time integral were measured on five plantar segments: medial forefoot (MFF), lateral forefoot (LFF), medial midfoot (MMF), lateral midfoot (LMF), and heel. Maximum ankle dorsiflexion was also recorded using the Plug in Gait marker set. Results: All participants maintained heel-toe gait in all walking conditions. The peak pressure on the MFF during downhill slope walking was lower than that during ground and uphill walking, whereas the peak pressure on the MFF during uphill slope walking was similar to that during ground walking at each walking speed. The peak pressures on the heel were similar for different walking slopes at each walking speed. The peak pressures on the MFF and heel increased with an increase in walking speed. The pressure-time integral of the MFF did not show significant changes at different walking speeds and slopes. The pressure-time integral of the heel increased with an increase in walking slope and decrease in walking speed. Conclusions: Different walking speeds and slopes affected the pedobarographic characteristics of young healthy adults. Downhill walking with slower speed appeared to be beneficial to reduce or optimize MFF pressures, while downhill walking at a comfortable speed would be helpful to reduce or optimize heel pressures. The findings of this study have clinical implications in recommending activities to patients with foot pressure-related symptoms and disorders. [ABSTRACT FROM AUTHOR]

We examined the effect of increased anterior subject positioning toward the dynamometer’s footplate during maximal voluntary isometric contractions (MVCs) on the joint moment, rotation and rate of torque development (RTD). Fourteen subjects, with their hip flexed (110°) and knee fully extended (180°), underwent ramp maximal and rapid voluntary isometric plantar flexion contractions at 4 different positions (0, 3, 6 and 8 cm; randomized). At position “0 cm”, the foot was in full contact with the footplate; at the additional positions, the chair was moved forward. Body kinematics (VICON) and kinetics (HUMAC Norm, PEDAR) were captured synchronously during MVCs and RTDs. The results showed that the maximal exerted joint moment was significantly (p<0.01) increased by >32% from the 0-cm to 8-cm position (126 and 172 Nm, respectively); however, at the “6 cm” and “8 cm” positions, no significant difference was found. The joint rotation was significantly (p<0.01) reduced by >50% (from 15.5 to 7.1°; 0–8 cm). The maxRTD was only significantly higher at “6 cm” compared with the “0 cm” position. The time to reach maxRTD showed shorter tendencies for the “8 cm” position than for all other positions. The results indicate an underestimation of the plantar flexor maximal force potential with the current measuring technique. This could be critical in pre-post study designs where a 2-cm alteration in the chair position can induce an error of ~9% in the joint moment. The joint rotation could be reduced but not completely eliminated. For position standardization purposes, a pressure >220 kPa under the subject’s foot is needed to achieve the maximal joint moment. We discussed the possible origins (fascicle length, neural drive) of the increased joint moment. [ABSTRACT FROM AUTHOR]

Gait variability is a sensitive metric for assessing functional deficits in individuals with mobility impairments. To correctly represent the temporal evolution of gait kinematics, nonlinear measures require extended and uninterrupted time series. In this study, we present and validate a novel algorithm for concatenating multiple time-series in order to allow the nonlinear analysis of gait data from standard and unrestricted overground walking protocols. The full-body gait patterns of twenty healthy subjects were captured during five walking trials (at least 5 minutes) on a treadmill under different weight perturbation conditions. The collected time series were cut into multiple shorter time series of varying lengths and subsequently concatenated using a novel algorithm that identifies similar poses in successive time series in order to determine an optimal concatenation time point. After alignment of the datasets, the approach then concatenated the data to provide a smooth transition. Nonlinear measures to assess stability (Largest Lyapunov Exponent, LyE) and regularity (Sample Entropy, SE) were calculated in order to quantify the efficacy of the concatenation approach using intra-class correlation coefficients, standard error of measurement and paired effect sizes. Our results indicate overall good agreement between the full uninterrupted and the concatenated time series for LyE. However, SE was more sensitive to the proposed concatenation algorithm and might lead to false interpretation of physiological gait signals. This approach opens perspectives for analysis of dynamic stability of gait data from physiological overground walking protocols, but also the re-processing and estimation of nonlinear metrics from previously collected datasets. [ABSTRACT FROM AUTHOR]

An objective analysis of the human movement can help both clinical assessment and sports performance. Kinovea is a free 2D motion analysis software that can be used to measure kinematic parameters. This low-cost technology has been used in sports sciences, as well as in the clinical and research fields. One interesting tool is that it can measure an object (or person) passing in front of the camera, taking into account the perspective between the camera and the recorded object. Although it has been validated as a tool to assess time-related variables, few studies assessed its validity compared to a Gold Standard; furthermore, its reliability in different perspectives has not been previously assessed. The main objective of this study is to determine the validity of the Kinovea software compared to AutoCAD, and its intra and inter-rater reliability in obtaining coordinates data; a second objective is to compare their results at 4 different perspectives (90°, 75°, 60° and 45°) and to assess the inter and intra rater reliability at each perspective. For this purpose, a wire structure figure in the shape of a human lower limb was designed and measured in AutoCAD; it was then recorded during a pendular motion with a video-camera placed at distance of 5 m and analyzed with Kinovea in the 4 perspectives (90°, 75°, 60° and 45°). Each frame was examined by three observers who made two attempts. A multiple approach was applied involving the analysis of the systematic error, with a two-way ANOVA 2x4; the relative reliability with Intraclass Correlation Coefficient (ICC) and the Coefficient of Variance (CV) (95% confidence interval); and the absolute reliability with the Standard Error (SE). The results indicate that the Kinovea software is a valid and reliable tool that is able to measure accurately at distances up to 5 m from the object and at an angle range of 90°–45°. Nevertheless, for optimum results an angle of 90° is suggested. [ABSTRACT FROM AUTHOR]

A stable walking pattern is presumably essential to avoid falls. Stability of walking is most accurately determined by the short-term local dynamic stability (maximum Lyapunov exponent) of the body centre of mass. In many studies related to fall risk, however, variability of step width is considered to be indicative of the stability of the centre of mass during walking. However, other footfall parameters, in particular variability of stride time, have also been associated with increased risk for falling. Therefore, the aim of this study was to investigate the association between short-term local dynamic stability of the body centre of mass and different measures of footfall variability. Twenty subjects performed unperturbed walking trials on a treadmill and under increased (addition of 40% body weight) and decreased (harness system) demands to stabilise the body centre of mass. Association between stability of the centre of mass and footfall parameters was established using a structural equation model. Walking with additional body weight lead to greater instability of the centre of mass and increased stride time variability, however had no effect on step width variability. Supported walking in the harness system did not increase centre of mass stability further, however, led to a significant decrease of step width and increase in stride time variability. A structural equation model could only predict 8% of the variance of the centre of mass stability after variability of step width, stride time and stride length were included. A model which included only step width variability as exogenous variable, failed to predict centre of mass stability. Because of the failure to predict centre of mass stability in this study, it appears, that the stability of the centre of mass is controlled by more complex interaction of sagittal and frontal plane temporal and spatial footfall parameters, than those observed by standard variability measures. Anyway, this study does not support the application of step width variability as indicator for medio-lateral stability of the centre of mass during walking. [ABSTRACT FROM AUTHOR]

During development, motor skills are fundamental in supporting interactions with the external world. The ability to plan actions is a particularly important aspect of motor skill since it is involved in many daily activities. In this work, we studied the development of motor planning longitudinally in children with an older sibling with Autism Spectrum Disorder (ASD) who are at heightened risk (HR) for the disorder and children with no such risk (low risk; LR) using a shape sorter task. Children were observed at 14, 18, 24 and 36 months. Three HR children with a later diagnosis of ASD (HR-ASD) were analyzed separately from the rest of the sample. Behavioral and kinematic data indicated that precision demands significantly influenced children’s actions, and that children’s performance improved with age. No differences were found between the HR and LR groups, but a descriptive analysis of data from the three HR-ASD suggested differences in the variables describing children’s action (as reaching time and acceleration) as well as variables describing children’s performance (as the adjustment of the shapes). [ABSTRACT FROM AUTHOR]

Introduction: Measuring coronal plane gait kinematics of the pelvis and trunk during rehabilitation of participants with a lower extremity amputation is important to detect asymmetries in gait which are hypothesised as associated with secondary complaints. The aim of this study was to test the reproducibility and discriminant validity of a three-dimensional (3-D; inertial measurement units) and a two-dimensional (2-D; video-based) system. Methods: We tested the test-retest and inter-rater reproducibility of both systems and the 2-D system, respectively, in participants with a lower extremity amputation (group 1) and healthy subjects (group 2). The discriminant validity was determined with a within-group comparison for the 3-D system and with a between-group comparison for both systems. Results: Both system showed to be test-retest reliable, both in group 1 (2-D system: ICC3.1agreement 0.52–0.83; 3-D system: ICC3.1agreement 0.81–0.95) and in group 2 (3-D system: ICC3.1agreement 0.33–0.92; 2-D system: ICC3.1agreement 0.54–0.95). The 2-D system was also inter-rater reliable (group 1: ICC2.1agreement 0.80–0.92; group 2: ICC2.1agreement 0.39–0.90). The within-group comparison of the 3-D system revealed a statistically significant asymmetry of 0.4°-0.5° in group 1 and no statistically significant asymmetry in group 2. The between-group comparison revealed that the maximum amplitude towards the residual limb (MARL) in the low back (3-D system) and the (residual) limb—trunk angle (2-D system) were significantly larger with a mean difference of 1.2° and 6.4°, respectively, than the maximum amplitude of healthy subjects. However, these average differences were smaller than the smallest detectable change (SDC) of group 1 for both the MARL (SDCagreement: 1.5°) and the residual limb—trunk angle (SDCagreement: 6.7°-7.6°). Conclusion: The 3-D and 2-D systems tested in this study were not sensitive enough to detect real differences within and between participants with a lower extremity amputation and healthy subjects although promising reproducibility parameters for some of the outcome measures. [ABSTRACT FROM AUTHOR]

Although several studies have examined the effects of performing resistance training with different percentages of one-repetition maximum (1-RM), little is known of the neuromuscular effects and kinematics of lifting low to heavy loads with maximal movement velocity. The aim of this study is to compare muscle activation and kinematics in free-weight back squats with different loads. Thirteen resistance-training males (aged 24.2 ± 2.0 years, body mass 81.5 ± 9.1 kg, height 1.78 ± 0.06 m) with 6 ± 3 years of resistance-training experience conducted squats with 30%–100% of 1-RM. Barbell kinematics and electromyographic (EMG) activity of the vastus lateralis, vastus medialis, rectus femoris, semitendinosus, biceps femoris, and gluteus maximus were measured in the upward phase of each load. With increasing loads, the barbell velocity decreased, the upward phase duration increased, and the peak velocity occurred later. The muscle activation in all muscles increased with increasing loads but was not linear. In general, similar muscle activation in the prime movers was observed for loads between 40% and 60% of 1-RM and between 70% and 90% of 1-RM, with 100% of 1-RM being superior to the other loads when the loads were lifted at maximal intended velocity. However, the timing of maximal muscle activations was not affected by the different loadings for the quadriceps, but the timing was sequential and independent of loading (rectus femoris before vastus medial before vastus lateral). Maximal activation in the gluteus and semitendinosus increased with increasing loads. This means that for muscle activation, maximal lifting velocity may compensate for increased loads, which may allow resistance-trained athletes and individuals in rehabilitation to avoid heavy loads but still get the same muscle activation. [ABSTRACT FROM AUTHOR]

A robust and stratified pre-clinical natural knee model, which has the capability to more appropriately simulate the biomechanical environment in vivo, will deliver more efficient and reliable assessment of soft tissue interventions before clinical studies. In order to simulate the biomechanical function of the natural knee without the natural ligaments in place, there is a requirement to develop appropriate spring constraints for the natural knee model. Therefore, this study was to investigate the effect of spring constraints on the function and output of the natural porcine knee model, and determine the spring constraint which most closely replicated the function of the natural ligaments. Two linear compression springs with stiffnesses of 9 N/mm (spring-9) and 20 N/mm (spring-20) were set at different free lengths in the anterior-posterior (A/P) axis in a natural knee simulator. The kinematic (A/P displacement) and tribological properties (shear force) output of the simulator were compared at different spring settings. The most appropriate spring setting was determined by comparing the A/P displacement and shear force output at different spring settings with those of the all ligaments model. Spring-9 with a free length of 4 mm showed the minimal difference (-0.03±0.68 mm) in A/P displacement output and spring-20 with a free length of 5 mm showed the minimal difference (-0.10±0.73 mm) in A/P displacement output compared to the all ligament control. There was no statistical difference between the two minimal differences either in A/P displacement or in shear force (paired t-test, p = 0.58, and p = 0.68 respectively) when both spring settings matched most closely to the A/P kinematics of the intact knee. This indicated that both conditions were appropriate spring constraints settings in the A/P direction for the natural porcine knee model. [ABSTRACT FROM AUTHOR]

Head collisions in sport can result in catastrophic injuries to the cervical spine. Musculoskeletal modelling can help analyse the relationship between motion, external forces and internal loads that lead to injury. However, impact specific musculoskeletal models are lacking as current viscoelastic values used to describe cervical spine joint dynamics have been obtained from unrepresentative quasi-static or static experiments. The aim of this study was to develop and validate a cervical spine musculoskeletal model for use in axial impacts. Cervical spine specimens (C2-C6) were tested under measured sub-catastrophic loads and the resulting 3D motion of the vertebrae was measured. Specimen specific musculoskeletal models were then created and used to estimate the axial and shear viscoelastic (stiffness and damping) properties of the joints through an optimisation algorithm that minimised tracking errors between measured and simulated kinematics. A five-fold cross validation and a Monte Carlo sensitivity analysis were conducted to assess the performance of the newly estimated parameters. The impact-specific parameters were integrated in a population specific musculoskeletal model and used to assess cervical spine loads measured from Rugby union impacts compared to available models. Results of the optimisation showed a larger increase of axial joint stiffness compared to axial damping and shear viscoelastic parameters for all models. The sensitivity analysis revealed that lower values of axial stiffness and shear damping reduced the models performance considerably compared to other degrees of freedom. The impact-specific parameters integrated in the population specific model estimated more appropriate joint displacements for axial head impacts compared to available models and are therefore more suited for injury mechanism analysis. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to measure the movement of the cervical spine in healthy volunteers and patients with cervical spondylosis (CS) and describe the actual motion of the cervical spine using a three-dimensional (3D) CT reconstruction method. The results can enrich current biomechanical data of cervical spine and help to find the differences between the noted two groups. Materials and methods: 20 healthy volunteers underwent CT examination ranging from the clivus of the occiput (Oc) to the top of first thoracic vertebrae (T1) in a neutral position with left or right maximal axial rotation, while 26 CS patients received the same CT scan procedures in the neutral position with left and right maximum rotation. Subsequently, the three-dimensional images of the occiput and every cervical vertebrae (C1-C7) were reconstructed using medical software. 3 virtual non-collinear markers were placed on the prominent structures of foramen magnum and every cervical vertebrae. Then, the 3D orthogonal spatial coordinates were defined with these anatomical markers to represent the orientation and position of every vertebra. Segmental relative motions were calculated using Cardan angles in the 3D spatial coordinates. Finally, the differences between the two groups were analyzed with statistical software SPSS. Results: The cervical spine exhibited complicated 3D movements, which could be adequately described using the three-dimensional CT reconstruction method. Reliability analysis of the 3D CT reconstruction method showed inter-rater ICC of 0.90–0.99 and intra-rater ICC of 0.91–0.98, suggesting very good consistency. Besides, the rotation at the upper cervical spine (Oc-C2) took up at least 60% of the total cervical rotation. The coupled lateral bending movement of the upper cervical spine was opposite to the major motion, while the movement of the lower cervical spine followed the same direction as that of the major motion. Oc to C5 segments were all coupled with the back-extension movement. The relative translations of all adjacent segments in each direction were minimal. CS patients showed a significant decrease in the movement of the C4-C5 segment compared with healthy volunteers. Conclusion: The motion of the cervical spine was complicated and three-dimensional. The CT reconstruction method employed here was good at describing such movement. The 3D CT reconstruction method exhibited high reproducibility when measuring cervical spine movement. CS patients and healthy volunteers showed significant differences in the movement of some segments. [ABSTRACT FROM AUTHOR]

Posterolateral corner (PLC) structures of the knee joint comprise complex anatomical soft tissues that support static and dynamic functional movements of the knee. Most previous studies analyzed posterolateral stability in vitro under static loading conditions. This study aimed to evaluate the contributions of the lateral (fibular) collateral ligament (LCL), popliteofibular ligament (PFL), and popliteus tendon (PT) to cruciate ligament forces under simulated dynamic loading conditions by using selective individual resection. We combined medical imaging and motion capture of healthy subjects (four males and one female) to develop subject-specific knee models that simulated the 12 degrees of freedom of tibiofemoral and patellofemoral joint behaviors. These computational models were validated by comparing electromyographic (EMG) data with muscle activation data and were based on previous experimental studies. A rigid multi-body dynamics simulation using a lower extremity musculoskeletal model was performed to incorporate intact and selective resection of ligaments, based on a novel force-dependent kinematics method, during gait (walking) and squatting. Deficiency of the PLC structures resulted in increased loading on the posterior cruciate ligament and anterior cruciate ligament. Among PLC structures, the PT is the most influential on cruciate ligament forces under dynamic loading conditions. [ABSTRACT FROM AUTHOR]

This study tested the effect of two block setting conditions i.e., the usual block setting [US] and an anthropometry-driven block setting [AS] on the kinematic and kinetic parameters of the sprint start. Furthermore, we verified whether this effect is influenced by the relative lengths of the sprinter’s trunk and lower limbs i.e., the Cormic Index by subdividing sprinters into brachycormic, metricormic and macrocormic groups. Forty-two sprinters performed 6 maximal-effort 10 m sprints using the US and AS conditions. Dynamometric starting blocks measured forces generated by the sprinters. The times at 5 m and 10 m in the sprint trials were measured with photocells. Results showed that the anteroposterior block distances were significantly different between the two conditions (P<0.001). Across the sample, the horizontal block velocity, the rear peak force, the rear force impulse, the total force impulse, the horizontal block power, the ratio of horizontal to resultant impulse in the rear block, the first and second step lengths and the times at 5 m and 10 m improved in AS vs. US (P values from 0.05 to 0.001). Considering the interaction between the block setting condition and the Cormic Index, the rear peak force and the rear force impulse were significantly increased in the metricormic and brachycormic groups (P≤0.001) and the metricormic group (P<0.001), respectively. Kinetic variables in the rear block and the difference (Delta) in the front block/starting line distance between US and AS were related with each other (Adjusted R2 values from 0.07 to 0.36). In conclusion, AS was associated with improvement in the kinematic and kinetic parameters of the sprint start performance vs. US; however, AS is apparently best suited for metricormic sprinters. Further work is needed to verify how the sprint start kinetic and kinematic parameters are related to the front block/starting line distance and whether a block setting driven by the sprinter’s Cormic Index is able to improve sprint start performance. [ABSTRACT FROM AUTHOR]

Recent research has suggested that visual discrimination and detection may be enhanced during movement preparation and execution, respectively. The current study examined if visual perceptual processing is augmented prior to or during a movement through the use of an Inspection Time (IT) task. The IT task involved briefly presenting (e.g., 15–105 ms) a "pi" figure with differing leg lengths, which was then immediately masked for 400 ms to prevent retinal afterimages. Participants were subsequently required to choose which of the two legs was longer. In Experiment 1, participants (n = 28) completed the IT task under three movement conditions: no-movement (NM), foreperiod (FP), and peak velocity (PV). In the NM condition, participants solely engaged in the IT paradigm. In the FP condition, the IT stimulus was presented prior to movement execution when response planning was expected to occur. Finally, in the PV condition, participants made a rapid movement to a target, and the IT stimulus was presented when their limb reached peak velocity. In Experiment 2, participants (n = 18) also performed the IT task in the PV and NM condition; however, vision of the limb's motion was made available during the PV trials (PV-FV) to investigate the potential influence of visual feedback on IT performance. Results showed no significant differences in performance in the IT task between the NM and FP conditions, suggesting no enhancement of visual processing occurred due to response preparation (Experiment 1). However, IT performance was significantly poorer in the PV condition in comparison to both the NM and FP conditions (Experiment 1), and was even worse when visual feedback was provided (Experiment 2). Together, these findings suggest that visual perceptual processing is degraded during execution of a fast, goal-directed movement. [ABSTRACT FROM AUTHOR]

Looking for new opportunities in mechanical design, we are interested in studying the kinematic behaviour of biological joints. The real kinematic behaviour of the elbow of quadruped animals (which is submitted to high mechanical stresses in comparison with bipeds) remains unexplored. The sheep elbow joint was chosen because of its similarity with a revolute joint. The main objective of this study is to estimate the effects of elbow simplifications on the prediction of joint reaction forces in inverse dynamic simulations. Rigid motions between humerus and radius-ulna were registered during full flexion-extension gestures on five cadaveric specimens. The experiments were initially conducted with fresh specimens with ligaments and repeated after removal of all soft tissue, including cartilage. A digital image correlation system was used for tracking optical markers fixed on the bones. The geometry of the specimens was digitized using a 3D optical scanner. Then, the instantaneous helical axis of the joint was computed for each acquisition time. Finally, an OpenSim musculoskeletal model of the sheep forelimb was used to quantify effects of elbow joint approximations on the prediction of joint reaction forces. The motion analysis showed that only the medial-lateral translation is sufficiently large regarding the measuring uncertainty of the experiments. This translation assimilates the sheep elbow to a screw joint instead of a revolute joint. In comparison with fresh specimens, the experiments conducted with dry bone specimens (bones without soft tissue) provided different kinematic behaviour. From the results of our inverse dynamic simulations, it was noticed that the inclusion of the medial-lateral translation to the model made up with the mean flexion axis does not affect the predicted joint reaction forces. A geometrical difference between the axis of the best fitting cylinder and the mean flexion axis (derived from the motion analysis) of fresh specimens was highlighted. This geometrical difference impacts slightly the prediction of joint reactions. [ABSTRACT FROM AUTHOR]

3D joint kinematics can provide important information about the quality of movements. Optical motion capture systems (OMC) are considered the gold standard in motion analysis. However, in recent years, inertial measurement units (IMU) have become a promising alternative. The aim of this study was to validate IMU-based 3D joint kinematics of the lower extremities during different movements. Twenty-eight healthy subjects participated in this study. They performed bilateral squats (SQ), single-leg squats (SLS) and countermovement jumps (CMJ). The IMU kinematics was calculated using a recently-described sensor-fusion algorithm. A marker based OMC system served as a reference. Only the technical error based on algorithm performance was considered, incorporating OMC data for the calibration, initialization, and a biomechanical model. To evaluate the validity of IMU-based 3D joint kinematics, root mean squared error (RMSE), range of motion error (ROME), Bland-Altman (BA) analysis as well as the coefficient of multiple correlation (CMC) were calculated. The evaluation was twofold. First, the IMU data was compared to OMC data based on marker clusters; and, second based on skin markers attached to anatomical landmarks. The first evaluation revealed means for RMSE and ROME for all joints and tasks below 3°. The more dynamic task, CMJ, revealed error measures approximately 1° higher than the remaining tasks. Mean CMC values ranged from 0.77 to 1 over all joint angles and all tasks. The second evaluation showed an increase in the RMSE of 2.28°– 2.58° on average for all joints and tasks. Hip flexion revealed the highest average RMSE in all tasks (4.87°– 8.27°). The present study revealed a valid IMU-based approach for the measurement of 3D joint kinematics in functional movements of varying demands. The high validity of the results encourages further development and the extension of the present approach into clinical settings. [ABSTRACT FROM AUTHOR]

Background: The effect of cadence and work rate on the joint specific power production in cycling has previously been studied, but research has primarily focused on cadences above 60 rpm, without examining the effect of low cadence on joint contribution to power. Purpose: Our purpose was to investigate joint specific power production in recreational and elite cyclists during low- and moderate cycling at a range of different cadences. Methods: 18 male cyclists (30.9 ± 2.7 years with a work rate in watt at lactate threshold of 282.3 ± 9.3 W) performed cycling bouts at seven different pedalling rates and three intensities. Joint specific power was calculated from kinematic measurements and pedal forces using inverse dynamics at a total of 21 different stages. Results: A main effect of cadence on the relative to the total joint power for hip-, knee- and ankle joint power was found (all p < 0.05). Increasing cadence led to increasing knee joint power and decreasing hip joint power (all p < 0.05), with the exception at low cadence (<60 rpm), where there was no effect of cadence. The elite cyclists had higher relative hip joint power compared to the recreational group (p < 0.05). The hip joint power at moderate intensity with a freely chosen cadence (FCC) was lower than the hip joint power at low intensity with a low cadence (<60 rpm) (p < 0.05). Conclusion: This study demonstrates that there is an effect of cadence on the hip- and knee joint contribution in cycling, however, the effect only occurs from 60 rpm and upward. It also demonstrates that there is a difference in joint contribution between elite- and recreational cyclists, and provide evidence for the possibility of achieving higher relative hip joint power at low intensity than moderate intensity by altering the cadence. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this study was to investigate the effect of different incline-speed combinations, at equal external power outputs, on the mechanics and energetics of the double-poling (DP) technique in cross-country skiing. Methods: Fourteen elite male cross-country skiers performed treadmill DP on roller-skis at low, moderate, and high mean external power outputs (Pmean) up a shallow incline (5%, INC5), at which DP is preferred, and up a steep incline (12%, INC12), at which DP is not preferred. Speed was set to produce equal Pmean at both inclines. From recorded kinematics and dynamics, arm power (Parm) and trunk+leg power (PT+L) were derived, as were pole propulsion power (Ppole) and body mechanical energy perpendicular to the treadmill surface (Ebody⊥). Results: Over a locomotion cycle, the arms contributed 63% to Pmean at INC5 but surprisingly only 54% at INC12 (P<0.001), with no effect of Pmean (P = 0.312). Thus, the trunk and legs contributed substantially to Pmean both at INC5 (37%) and INC12 (46%). At both inclines, PT+L generation during the swing phase increased approximately linearly with Pmean, which increased Ebody⊥. Within the poling phase, ~30–35% of the body energy which was developed during the preceding swing phase was transferred into propulsive pole power on both inclines. At INC5, the amount of negative PT+L during the poling phase was larger than at INC12, and this difference increased with Pmean. Conclusions: The considerable larger amount of negative PT+L during poling at INC5 than at INC12 indicate that the legs and trunk generate more power than ‘necessary’ during the swing phase and thus must absorb more energy during the poling phase. This larger surplus of PT+L at INC5 seems necessary for positioning the body and poles so that high Parm generation can occur in a short time. At INC12, less Parm is generated, probably due to less advantageous working conditions for the arms, related to body and pole positioning. These incline differences seem linked to shorter swing and longer poling times during steep uphill DP, which are due to the increased influence of gravity and slower speed at steep inclines. [ABSTRACT FROM AUTHOR]

The benefits of using longer than self-selected poles have been shown in double poling, but these potential benefits have not been examined in the gear 3 ski skating sub-technique (G3), during which the poling movement is very similar to double poling. The aim of this study was to examine the effect of longer than self-selected poles on physiological and perceptual responses in the G3 sub-technique. Ten cross-country skiers and biathletes (VO2max 72.4 ± 3.0 ml∙min-1∙kg-1, age 20.1 ± 2.8 years, height 1.81 ± 0.03 m and weight 73.1 ± 4.6 kg) completed two tests, each with three different submaximal intensities, during roller skiing using the G3 technique. The first test was carried out at a fixed speed (10 km∙h-1) and the skiers performed two intervals of 5 min at 7, 9 and 11% inclination on a roller ski treadmill with self-selected poles (SSP) and 7.5 cm longer poles (LP) at each step. The second test had a fixed inclination of 4% and speeds of 14, 17 and 20 km∙h-1, also performed with SSP and LP at each step. At fixed speed, the oxygen uptake was 2.7% lower (P = 0.005) and the gross efficiency (GE) 2.1% higher (P = 0.01) with LP than with SSP at the steepest inclination of 11%. At fixed inclination, the oxygen uptake was 2.1% lower (P = 0.01) and the GE was 4.1% higher (P = 0.03) with LP than with SSP at the highest speed of 20 km∙h-1. At 14 km∙h-1, the oxygen uptake was 3.0% lower (P = 0.05) and GE was 3.8% higher (P = 0.03) with LP than with SSP. Our novel findings show that longer poles in the G3 technique may enhance the efficiency of skiing. [ABSTRACT FROM AUTHOR]

A typical optical based gait analysis laboratory uses expensive stereophotogrammetric motion capture systems. The study aims to propose and validate an affordable gait analysis method using augmented reality (AR) markers with a single action camera. Image processing software calculates the position and orientation of the AR markers. Anatomical landmark calibration is applied on the subject to calibrate each of the anatomical points with respect to their corresponding AR markers. This way, anatomical points are tracked through AR markers using homogeneous coordinate transformations, and the further processing of gait analysis is identical with conventional solutions. The proposed system was validated on nine participants of varying age using a conventional motion capture system on simultaneously measured treadmill gait trials on 2, 3 and 4.5 km/h walking speeds. Coordinates of the virtual anatomical points were compared using the Bland-Altman analysis. Spatial-temporal gait parameters (step length, stride length, walking base, cadence, pelvis range of motion) and angular gait parameters (range of motion of knee, hip and pelvis angles) were compared between measurement systems by RMS error and Bland-Altman analysis. The proposed method shows some differences in the raw coordinates of virtually tracked anatomical landmarks and gait parameters compared to the reference system. RMS errors of spatial parameters were below 23 mm, while the angular range of motion RMS errors varies from 2.55° to 6.73°. Some of these differences (e.g. knee angle range of motion) is comparable to previously reported differences between commercial motion capture systems and gait variability. The proposed method can be a very cheap gait analysis solution, but precision is not guaranteed for every aspect of gait analysis using the currently exemplified implementation of the AR marker tracking approach. [ABSTRACT FROM AUTHOR]

Annotation of foot-contact and foot-off events is the initial step in post-processing for most quantitative gait analysis workflows. If clean force plate strikes are present, the events can be automatically detected. Otherwise, annotation of gait events is performed manually, since reliable automatic tools are not available. Automatic annotation methods have been proposed for normal gait, but are usually based on heuristics of the coordinates and velocities of motion capture markers placed on the feet. These heuristics do not generalize to pathological gait due to greater variability in kinematics and anatomy of patients, as well as the presence of assistive devices. In this paper, we use a data-driven approach to predict foot-contact and foot-off events from kinematic and marker time series in children with normal and pathological gait. Through analysis of 9092 gait cycle measurements we build a predictive model using Long Short-Term Memory (LSTM) artificial neural networks. The best-performing model identifies foot-contact and foot-off events with an average error of 10 and 13 milliseconds respectively, outperforming popular heuristic-based approaches. We conclude that the accuracy of our approach is sufficient for most clinical and research applications in the pediatric population. Moreover, the LSTM architecture enables real-time predictions, enabling applications for real-time control of active assistive devices, orthoses, or prostheses. We provide the model, usage examples, and the training code in an open-source package. [ABSTRACT FROM AUTHOR]

Background: Approximately 50 to 70% of post-stroke subjects present a reduction in the upper limb (UL) function even during the chronic phase. An adjuvant technique widely used in neurorehabilitation is elastic taping applications. However, its efficacy in UL treatment for post-stroke subjects still requires further investigation. Objective: To verify the effects of elastic tape (ET) used on the paretic shoulder in upper limb (UL) performance during a drinking task. Method: A single-center randomized sham-controlled crossover trial randomized thirteen post-stroke subjects with mild to moderate UL impairment for group allocation to receive first Sham Tape (ST) or first Elastic Tape (ET), with one month of washout. Kinematic measures of a drinking task were taken before and after each intervention (elastic and sham tape), using Three-Dimensional Motion Analysis, and studied using feature analysis and Statistical Parametric Mapping. Outcome measures included spatiotemporal variables, scalar kinematic parameters (starting angles, range of motion—ROM, and endpoint angles) and time-normalized kinematic waveforms of trunk and UL joint angles (scapulothoracic, humerothoracic and elbow). Results: Elastic tape provided common modifications throughout the task (shoulder more towards midline, reduced scapula protraction and trunk flexion) and important alterations at specific time-instants. At the end of the reaching phase, for both groups (ET and ST), the elastic tape increased elbow extension [ET: CI = 12.57 (6.90 to 18.17), p<0.001; ST: CI: 12.89 (6.79 to 18.98), p<0.001). At the end of transporting the glass to the mouth, patients who underwent the elastic tape intervention presented more shoulder elevation [ET: CI = 16.40 (4.28 to 28.52), p = 0.007; ST: CI: 15.13 (5.79 to 24.48), p = 0.002)]. Moreover, an increase of elbow extension at the end of transporting the glass to the table was observed for both groups [ET: CI = 8.13 (1.48 to 14.79), p = 0.014; ST: CI: 8.20 (4.03 to 12.38), p<0.001)]. However, no changes in the spatiotemporal parameters were observed for both groups during all the phases of the task (p>0.05). Conclusion: The ET changed UL joint motions and posture during a drinking task in chronic hemiparetic subjects, which defines its role as an adjuvant therapy. [ABSTRACT FROM AUTHOR]

With an emphasis on ballistic movements, an accurately anticipated neural control is an essential prerequisite to deliver a motor response coincidentally with the event of ground contact. This study investigated how previous knowledge of the ground condition affects proactive and reactive motor control in drop jumps (DJ). Thereby, human anticipatory capacity of muscle activation was investigated regarding neuromuscular activation, joint kinematics and peak forces associated with DJ performance. In 18 subjects, the effect of knowledge of two different surface conditions during DJs was evaluated. Peak force, ground-contact-time (GCT), rate of force development (RFD) and jump height were assessed. Electromyographic (EMG) activities of the m. soleus (SOL) and gastrocnemius medialis (GM) were assessed for 150ms before (PRE) and during ground contact (GC) for the short-, medium-, and long-latency responses. Ankle and knee joint kinematics were recorded in the sagittal plane.In the unknown conditions peak force, RFD and jump height declined, GCT was prolonged, proactive EMG activity (PRE) in SOL and GM was diminished (P<0.05). During GC, a decline in EMG activity in the unknown condition was manifested for SOL and GM for the SLR, MLR and LLR (P<0.05). Ankle and knee joint deflections during GC were increased in the unknown vs. known condition (P<0.05). Peak force, RFD and jump height were positively correlated to GM-EMG in PRE, SLR, MLR and LLR (P<0.05). Results revealed that proactive and reactive modulations in muscle activity prior and during GC are interrelated to the force-time characteristics and height of the jumps. The unknown condition revealed a comparable neuromuscular activity during pre-activation for both conditions, followed by an inhibition in the subsequent phase after touch down. These findings underline that anticipation is a determining factor influencing timing and adjustment of motor responses to accomplish ballistic movements regarding precision and performance. [ABSTRACT FROM AUTHOR]

Human ageing is accompanied by a progressive decline in leg-extensor power (LEP). LEP is typically measured with specialized and expensive equipment, which limits the large-scale applicability. Previously, sensor-based trunk kinematics have been used to estimate the vertical power required to elevate the body’s center of mass during functional tests, but the link with LEP and age remains to be investigated. Therefore, we investigated whether a body-fixed sensor-based analysis of power during stair ascent (SA) and sit-to-stand (STS) is positively related to LEP and whether its ability to detect age-related declines is similar. In addition, the effect of load during SA and STS was investigated. 98 adults (20–70 years) performed a leg press to assess LEP, SA and 5-repetition STS tests. In SA and STS, two conditions were tested: unloaded and loaded (+10% body mass). An inertial measurement unit was used to analyze (sub)-durations and vertical power. SA and STS power were more related to LEP than duration parameters (i.e. 0.80–0.81 for power and -0.41 –-0.66 for duration parameters, p < 0.05). The average annual age-related percent change was higher in SA power (-1.38%) than in LEP (-0.86%) and STS power (-0.38%) (p < 0.05). Age explained 29% in SA power (p < 0.001), as opposed to 14% in LEP (p < 0.001) and a non-significant 2% in STS power (p = 0.102). The addition of 10% load did not influence the age-related decline of SA and STS power nor the relationship with LEP. These results demonstrate the potential of SA tests to detect age-related deterioration in neuromuscular function. SA seems more sensitive to detect age-related changes than LEP, probably because of the additional balance component and plantar- and dorsiflexor activity. On the contrary, STS is less sensitive to age-related changes because of a ceiling effect in well-functioning adults. [ABSTRACT FROM AUTHOR]

Functional methods identify joint centres as the centre of rotation (CoR) of two adjacent movements during an ad-hoc movement. The methods have been used for functionally determining hip joint centre in gait analysis and have revealed advantages compared to predictive regression techniques. However, the current implementation of functional methods hinders its application in clinical use when subjects have difficulties performing multi-plane movements over the required range. In this study, we systematically investigated whether functional methods can be used to localise the CoR during a quasi-planar movement. The effects of the following factors were analysed: the algorithms, the range and speed of the movement, marker cluster location, marker cluster size and distance to the joint centre. A mechanical linkage was used in our study to isolate the factors of interest and give insight to variation in implementation of functional methods. Our results showed the algorithms and cluster locations significantly affected the estimate results. For all algorithms, a significantly positive relationship between CoR errors and the distance of proximal cluster coordinate location to the joint centre along the medial-lateral direction was observed while the distal marker clusters were best located as close as possible to the joint centre. By optimising the analytical and experimental factors, the transformation algorithms achieved a root mean square error (RMSE) of 5.3 mm while the sphere fitting methods yielded the best estimation with an RMSE of 2.6 mm. The transformation algorithms performed better in presence of random noise and simulated soft tissue artefacts. [ABSTRACT FROM AUTHOR]

Introduction: From among many studies observing the walking pattern throughout pregnancy, only two items monitor the influence of pregnancy on the movement system during gait considering the period before gestation. Research question: Does the women’s gait pattern at the end of the first trimester undergo changes in comparison to body movement pattern before pregnancy? Methods: All subjects who met the inclusion criteria gave signed and informed consent before the study. Two experimental sessions were arranged according to the same protocol: (P0) before pregnancy and (P1) at the end of the first trimester of pregnancy (12th week of gestation). At first the anthropometric measures were taken. Then, walking trials at a self-selected speed along a walkway were registered with Vicon 250 (Oxford Metrics Ltd.; Oxford, UK) and FreeMED force platform (Sensor Medica, Italy). Results: An analysis of anthropometric parameters in 12th pregnancy week demonstrated significant changes in mean values of waist circumference and waist to hip ratio as well as waist to height ratio indexes compared to the results before pregnancy. No significant differences were found in the basic kinematic gait parameters between experimental conditions. Significant increase of mean inter—ankle distance during double support phase occurred during the first trimester of pregnancy. Also, the ratio of the ankle separation width to the pelvic width was noticeably higher in gestation. Then, angular changes of the pelvis in coronal and transverse planes throughout gait cycle during pregnancy demonstrated significant differences compared to those measured before pregnancy. At the same time in the first trimester of pregnancy no adaptive changes in the pattern of feet loading take place. Significance: Since our study is of longitudinal character, in the course of pregnancy we expect compensatory mechanisms more clearly demonstrated. Therefore, we hope to identify a strategy of the gravid body progression in space. [ABSTRACT FROM AUTHOR]

The coordination of the human musculoskeletal system is deeply influenced by its redundant structure, in both kinematic and dynamic terms. Noticing a lack of a relevant, thorough treatment in the literature, we formally address the issue in order to understand and quantify factors affecting the motor coordination. We employed well-established techniques from linear algebra and projection operators to extend the underlying kinematic and dynamic relations by modeling the redundancy effects in null space. We distinguish three types of operational spaces, namely task, joint and muscle space, which are directly associated with the physiological factors of the system. A method for consistently quantifying the redundancy on multiple levels in the entire space of feasible solutions is also presented. We evaluate the proposed muscle space projection on segmental level reflexes and the computation of the feasible muscle forces for arbitrary movements. The former proves to be a convenient representation for interfacing with segmental level models or implementing controllers for tendon driven robots, while the latter enables the identification of force variability and correlations between muscle groups, attributed to the system’s redundancy. Furthermore, the usefulness of the proposed framework is demonstrated in the context of estimating the bounds of the joint reaction loads, where we show that misinterpretation of the results is possible if the null space forces are ignored. This work presents a theoretical analysis of the redundancy problem, facilitating application in a broad range of fields related to motor coordination, as it provides the groundwork for null space characterization. The proposed framework rigorously accounts for the effects of kinematic and dynamic redundancy, incorporating it directly into the underlying equations using the notion of null space projection, leading to a complete description of the system. [ABSTRACT FROM AUTHOR]

Background: Low-velocity motor vehicle crashes often lead to severe and chronic neck disorders also referred to as whiplash-associated disorders (WAD). The etiology of WAD is still not fully understood. Many studies using a real or simulated collision scenario have focused on rear-end collisions, whereas the kinematics and muscular responses during frontal-oblique collisions have hardly been investigated. In particular for rear-end collisions, drivers were shown to have a higher WAD risk than front seat passengers. Yet, independently from the impact direction, neither the muscular nor the kinematic responses of drivers and front seat passengers have been compared to date, although some findings indicate that the neck muscles have the potential to alter the head and neck kinematics, and that the level of neck muscle activity during impact may be relevant for the emergence of WAD. Objective: In this study, we quantitatively examined the subjects’ neck muscle activity during low-velocity left-frontal-oblique impacts to gain further insights into the neuromuscular mechanism underlying whiplash-like perturbations that may lead to WAD. Methods: In a within-subject study design, we varied several impact parameters to investigate their effect on neck muscle response amplitude and delay. Fifty-two subjects experienced at least ten collisions while controlling for the following parameters: change in velocity Δv (3 / 6 km/h), seating position (driver / front seat passenger), and deliberate pre-tension of the musculature (tense / relaxed) to account for a potential difference between an expected and an unexpected crash. Ten of the 52 subjects additionally ran the same experimental conditions as above, but without wearing a safety belt. Findings: There were significant main effects of Δv and muscle pre-tension on the reflex amplitude but not of seating position. As for the reflex delay, there was a significant main effect of muscle pre-tension, but neither of Δv nor of seating position. Moreover, neither the safety belt nor its asymmetrical orientation had an influence on the reflexive responses of the occupants. Conclusion: In summary, we did not find any significant differences in the reflex amplitude and delay of the neck musculature between drivers and front seat passengers. We therefore concluded that an increased risk of the driver sustaining WAD in frontal-oblique collisions, if it exists, cannot be due to differences in the reflexive responses. [ABSTRACT FROM AUTHOR]

Objective: We aimed to investigate the correlations between Upper Extremity Musculoskeletal Symptoms (MSD) and joint kinematics while playing the piano, as well as correlations between MSD and psychosocial, professional and personal habits, and bio-demographic risk factors of piano students. Method: This cross-sectional study included 15 piano students. The research tools included 3D motion capture, anthropometric measurements, and questionnaires for obtaining data about MSD, psychological, and personal factors. Results: The piano students recruited for this study experienced a variety of MSD during the past 12 months, with a particularly high prevalence of neck pain (80%). Extreme wrist extension and/or elbow flexion while playing the piano also correlated with MSD. Additionally, this study identified correlations between MSD and hand span (r = -.69, p≤.004) and number of playing hours per week (r = .58, p≤.024). Conclusions: Anthropometric factors and playing patterns should be considered together with well-known MSD risk factors, like extreme and repetitive movements. However, considering each joint singularly might not be sufficient to prevent the development of MSD when instructing the piano player; accordingly, joint synchronization should also be considered. [ABSTRACT FROM AUTHOR]

Patellofemoral pain (PFP) is one of the most common overuse injuries of the knee. Previous research has found that individuals with PFP exhibit differences in peak hip kinematics; however, differences in peak knee kinematics, where the pain originates, are difficult to elucidate. To better understand the mechanism behind PFP, we sought to characterize differences in knee gait kinematic waveform patterns in individuals with PFP compared to healthy individuals using fast Fourier transform (FFT). Sixteen control and sixteen individuals with PFP participated in a fast walk protocol. FFT was used to decompose the sagittal, frontal and transverse plane knee gait waveforms into sinusoidal signals. A two-way ANOVA and Bonferroni post hoc analysis compared group, limb and interaction effects on sagittal, frontal and transverse amplitude, frequency and phase components between control and PFP individuals gait waveforms. Differences in frequency and phase values were found in the sagittal and frontal plane knee waveforms between the control and PFP groups. The signal-to-noise ratio also reported significant differences between the PFP and control limbs in the sagittal (p<0.01) and frontal planes (p = 0.04). The findings indicate that differences in gait patterns in the individuals with PFP were not the result of amplitude differences, but differences attributed to temporal changes in gait patterns detected by the frequency and phase metrics. These changes suggest that individuals with PFP adopted a more deliberate, stiffer gait and exhibit altered joint coordination. And the FFT technique could serve as a fast, quantifiable tool for clinicians to detect PFP. [ABSTRACT FROM AUTHOR]

Elucidating whether there is a correlation between biomechanical functions and histomorphometric data in the rat sciatic nerve crush injury model would contribute to an accurate evaluation of the regeneration state without sacrificing animals. The gold standard for functional evaluation is the sciatic functional index (SFI) despite there being intrinsic shortcomings. Kinematic analysis is considered a reliable and sensitive approach for functional evaluation, most commonly assessed as ankle angle at various phases of a gait cycle. Studies utilizing the toe angle for functional evaluation are scarce, and changes in the toe angle following surgery remain unknown. The present study assessed correlations of ankle angle, toe angle and SFI with histomorphometric data, aiming to determine which parameters most accurately reflect changes in histomorphometric data over time. Six Lewis rats were designated as the control group. 30 animals received surgery, six of them were randomly selected on the first, second, third, fourth, and sixth week after surgery for measurements of ankle and toe angles in the “toe-off” phase, and for evaluation of SFI. Histomorphometric analysis were also performed, to determine the number of myelinated nerve fibers, diameters of myelinated nerve fibers, axon diameters, and myelin sheath thicknesses. Furthermore, we investigated changes in ankle angle, toe angle, SFI, and histomorphometric data over time, as well as correlations between ankle angle, toe angle, and SFI with histomorphometric data. The results revealed that changes in SFI, ankle angle, and toe angle highly correlate with histomorphometric data in the rat sciatic nerve crush injury model. Toe angle reflected changes in histomorphometric data with time more precisely than ankle angle or SFI did, and ankle angle was a better prognostic parameter than SFI. [ABSTRACT FROM AUTHOR]

Introduction: The translation of the navicular bone is thought to be a representative surrogate measure to assess foot pronation and hence foot function; however, it is not known how it is related to multi-segment foot kinematics. Methods: Cranio-caudal (NCC) and medio-lateral (NML) navicular translation and multi-segment foot kinematics from the Oxford Foot Model (OFM) were simultaneously assessed during the stance phase of walking in 20 healthy adults. Relationships to forefoot to hindfoot (FFtoHF), hindfoot to tibia (HFtoTBA) and global hindfoot (HFL) motion were explored by cross-correlations at zero phase shift. Results: FFtoHF sagittal, transversal and frontal plane angles showed median cross correlations of -0.95, 0.82 and 0.53 with NCC and of 0.78, -0.81 and -0.90 with NML. HFtoTBA transversal and frontal plane angles had correlations of 0.15 and 0.74 with NCC and of -0.38 and -0.83 with NML. The HFL frontal plane angle showed correlations of 0.41 and -0.44 with NCC and NML, respectively. Discussion: The strongest relationships were found between FFtoHF sagittal plane angles and NCC and between FFtoHF frontal plane angles and NML. However, cranio-caudal and medio-lateral navicular translation seem to be reasonable surrogates for the triplanar motion between the fore- and hindfoot. The medial longitudinal arch dropped and bulged medially, while the forefoot dorsiflexed, abducted and everted with respect to the hindfoot and vice-versa. The lower cross-correlation coefficients between the rear foot parameters and NCC/NML indicated no distinct relationships between rearfoot frontal plane and midfoot kinematics. The validity of rearfoot parameters, like Achilles tendon or Calcaneal angle, to assess midfoot function must be therefore questioned. The study could also not confirm a systematic relationship between midfoot kinematics and the internal/external rotation between the hindfoot and the tibia. The measurement of navicular translation is suggested as an alternative to more complex multi-segment foot models to assess foot function. [ABSTRACT FROM AUTHOR]

Community dwelling stroke survivors most often fall while walking. Understanding how post-stroke individuals control mediolateral footpath during walking may help elucidate the mechanisms that contribute to walking instability. By applying the Uncontrolled Manifold (UCM) approach, we investigated (1) how post-stroke individuals coordinate lower-extremity joint motions to stabilize mediolateral footpath of the swing leg, and (2) how the inter-joint coordination in footpath stabilization correlates to their walking stability. Nine stroke subjects and nine healthy controls walked on a treadmill at four different speeds. UCM analysis partitions the variance of kinematic configurations across gait cycles into “good variance” (i.e., the variance component leading to a consistent footpath) or “bad variance” (i.e., the variance component leading to an inconsistent footpath). We found that both groups had a significantly greater “good” than “bad” variance (p<0.05) for most of the swing phase, suggesting that mediolateral footpath is an important variable stabilized by the central nervous system during walking. Stroke subjects had significantly greater relative variance difference (ΔV) (i.e. normalized difference between “good” and “bad” variance) (p<0.05), indicating a stronger kinematic synergy in footpath stabilization, than the controls. In addition, the kinematic synergy in mediolateral footpath stabilization is strongest during mid-swing but weakest during late swing in healthy gait. However, this phase-dependent strategy is preserved for mid-swing but not for late swing in stroke gait. Moreover, stroke and healthy subjects demonstrated different relationships between UCM and walking stability measures. A stronger kinematic synergy in healthy gait is associated with better walking stability whereas having more “good variance” or stronger kinematic synergy in stroke gait is associated with less walking stability. The current findings suggest that walking with too much “good variance” in people following stroke, despite no effect on the footpath, may adversely affect their walking stability to some extent. [ABSTRACT FROM AUTHOR]

Freezing, an episodic movement breakdown that goes from disrupted gait patterns to complete arrest, is a disabling symptom in Parkinson’s disease. Several efforts have been made to objectively identify freezing episodes (FEs), although a standardized methodology to discriminate freezing from normal movement is lacking. Novel mathematical approaches that provide information in the temporal and frequency domains, such as the continuous wavelet transform, have demonstrated promising results detecting freezing, although still with limited effectiveness. We aimed to determine whether a computerized algorithm using the continuous wavelet transform based on baseline (i.e. no movement) rather than on amplitude decrease is more effective detecting freezing. Twenty-six individuals with Parkinson’s disease performed two trials of a repetitive stepping-in-place task while they were filmed by a video camera and tracked by a motion capture system. The number of FEs and their total duration were determined from a visual inspection of the videos and from three different computed algorithms. Differences in the number and total duration of the FEs between the video inspection and each of the three methods were obtained. The accuracy to identify the time of occurrence of a FE by each method was also calculated. A significant effect of Method was found for the number (p = 0.016) and total duration (p = 0.013) of the FEs, with the method based on baseline being the closest one to the values reported from the videos. Moreover, the same method was the most accurate in detecting the time of occurrence, and the one reaching the highest sensitivity (88.2%). Findings suggest that threshold detection methods based on baseline and movement amplitude decreases capture different characteristics of Parkinsonian gait, with the first one being more effective at detecting FEs. Moreover, robust approaches that consider both time and frequency characteristics are more sensitive in identifying freezing. [ABSTRACT FROM AUTHOR]

Objectives: We investigated sex-based differences in speed, sub-technique selection, and kinematic patterns during low- (LIT) and high-intensity training (HIT) for classical cross-country (XC) skiing across varying terrain. Methods: Six male and six female elite XC skiers with an approximately 15% differences in VO2max (men: 68.9±2.9 mL·min-1·kg-1, women: 60.1±3.3 mL·min-1·kg-1) were monitored using a multi-sensor system to collect time-synchronised data of heart rate, speed, and multiple tri-axial inertial measurements units while XC skiing on a 5-km competition track. Results: Men skied 21% faster than women during HIT (5.9±0.3 m·s-1 vs. 4.9±0.2 m·s-1, P < .001), with the greatest difference (26%) while skiing on flat terrain, whereas skiing speed did not significantly differ between men and women during LIT. At similar instructed intensity and rating of perceived effort, women exhibited significantly higher relative heart rate (85±2% vs. 71±3% of maximum) and blood lactate levels (4.0±1.3 vs. 1.2±0.2 mmol/L) during LIT (all P < .001) than men, whereas physiological responses did generally not differ between the sexes during HIT. During both intensities and among both sexes, double poling (DP) was the sub-technique most used relative to distance, followed by miscellaneous sub-techniques (MISC), diagonal stride (DIA), kick double poling (DK) and herringbone (HRB). In relation to distance women used DIA more than men during LIT (22% vs. 17%, P = .009) and HIT (23% vs. 12%, P = .001), whereas men used MISC, including tucking and turning, more than women during LIT (39% vs. 25%, P = .017) and HIT (41% vs. 30%, P = .064). In particular, men used DP more than women while skiing the uphill sections during both LIT (24% vs. 11%, P = .015) and HIT (39% vs. 13%, P = .002). Conclusions: Our findings provide novel insights into sex-based differences in speed, sub-technique selection, and kinematic patterns during LIT and HIT for classical skiing. [ABSTRACT FROM AUTHOR]

Observing others’ actions desynchronizes electroencephalographic (EEG) rhythms and modulates corticospinal excitability as assessed by transcranial magnetic stimulation (TMS). However, it remains unclear if these measures reflect similar neurofunctional mechanisms at the individual level. In the present study, a within-subject experiment was designed to assess these two neurophysiological indexes and to quantify their mutual correlation. Participants observed reach-to-grasp actions directed towards a small (precision grip) or a large object (power grip). We focused on two specific time points for both EEG and TMS. The first time point (t1) coincided with the maximum hand aperture, i.e. the moment at which a significant modulation of corticospinal excitability is expected. The second (t2), coincided with the EEG resynchronization occurring at the end of the action, i.e. the moment at which a hypothetic minimum for action observation effect is expected. Results showed a Mu rhythm bilateral desynchronization at t1 with differential resynchronization at t2 in the two hemispheres. Beta rhythm was more desynchronized in the left hemisphere at both time points. These EEG differences, however, were not influenced by grip type. Conversely, motor potentials evoked by TMS in an intrinsic hand muscle revealed an interaction effect of grip and time. No significant correlations between Mu/Beta rhythms and motor evoked potentials were found. These findings are discussed considering the spatial and temporal resolution of the two investigated techniques and argue over two alternative explanations: i. each technique provides different measures of the same process or ii. they describe complementary features of the action observation network in humans. [ABSTRACT FROM AUTHOR]

Background: Up to 80% of wheelchair users are affected by shoulder pain. The Clinical Practice Guidelines for preservation of upper limb function following spinal cord injury suggest that using a proper wheelchair propulsion technique could minimize the shoulder injury risk. Yet, the exact relationship between the wheelchair propulsion technique and shoulder load is not well understood. Objective: This study aimed to examine the changes in shoulder loading accompanying the typical changes in propulsion technique following 80 min of low-intensity wheelchair practice distributed over 3 weeks. Methods: Seven able-bodied participants performed the pre- and the post-test and 56 min of visual feedback-based low-intensity wheelchair propulsion practice. Kinematics and kinetics of propulsion technique were recorded during the pre- and the post-test. A musculoskeletal model was used to calculate muscle force and glenohumeral reaction force. Results: Participants decreased push frequency (51→36 pushes/min, p = 0.04) and increased contact angle (68→94°, p = 0.02) between the pre- and the post-test. The excursion of the upper arm increased, approaching significance (297→342 mm, p = 0.06). Range of motion of the hand, trunk and shoulder remained unchanged. The mean glenohumeral reaction force per cycle decreased by 13%, approaching significance (268→232 N, p = 0.06). Conclusions: Despite homogenous changes in propulsion technique, the kinematic solution to the task varied among the participants. Participants exhibited two glenohumeral reaction force distribution patterns: 1) Two individuals developed high force at the onset of the push, leading to increased peak and mean glenohumeral forces 2) Five individuals distributed the force more evenly over the cycle, lowering both peak and mean glenohumeral forces. [ABSTRACT FROM AUTHOR]

The influence of age on spinal muscle activation patterns and its relation to kinematics is poorly understood. We aimed at understanding age-related changes to spine and trunk muscle activity in addition to spinal and lower limb kinematics during treadmill walking under various conditions. An observational study was conducted evaluating asymptomatic young (n = 10; 3F, 7M; 26.3±2.5yrs) and older (n = 9; 3F, 6M; 67.1±4.2yrs) adults’ treadmill walking at 2km/h and 4km/h, each at 0, 1, 5, and 10% inclination. Unilateral (right side) electromyography (EMG) was recorded from deep and superficial multifidus (intramuscular) and erector spinae and abdominal obliques (surface); trunk and leg kinematics were also measured. Muscle activity was characterised by peak amplitude and duration of activity, and the time-point of peak amplitude in the gait cycle (0–100%). Peak activation in older adults was lower for the superficial multifidus (p<0.0001) and higher for the thoracolumbar (p<0.001) and lumbar erector spinae (p<0.01). The duration of activation was longer in older adults for all muscles (p<0.05) except the superficial multifidus, and longer during faster walking for all participants. The time-point of peak amplitude in the gait cycle was earlier in older participants for the external obliques (p<0.05). Walking speed appeared to influence muscle activity more than inclination. Older adults used less spine, trunk and lower limb motion, except at the ankle. Age-related differences within multifidus and between paravertebral and trunk muscles were inconsistent. Walking at 4km/h at 5–10% inclination may specifically target the lumbar paravertebral muscles. [ABSTRACT FROM AUTHOR]

Musculoskeletal injuries (MSI) in the military reduce soldier capability and impose substantial costs. Characterizing biomechanical surrogates of MSI during commonly performed military tasks (e.g., load carriage) is necessary for evaluating the effectiveness of possible interventions to reduce MSI risk. This study determined the effects of body-borne load distribution, load magnitude, and walking speed on tibiofemoral contact forces. Twenty-one Australian Army Reserve soldiers completed a treadmill walking protocol in an unloaded condition and wearing four armor types (standard-issue and three prototypes) with two load configurations (15 and 30 kg) for a total of 8 armor x load ensembles. In each ensemble, participants completed a 5-minute warm-up, and then walked for 10 minutes at both moderate (1.53 m⋅s-1) and fast (1.81 m⋅s-1) speeds. During treadmill walking, three-dimensional kinematics, ground reaction forces, and muscle activity from nine lower-limb muscles were collected in the final minute of each speed. These data were used as inputs into a neuromusculoskeletal model, which estimated medial, lateral and total tibiofemoral contact forces. Repeated measures analyses of variance revealed no differences for any variables between armor types, but peak medial compartment contact forces increased when progressing from moderate to fast walking and with increased load (p<0.001). Acute exposure to load carriage increased estimated tibiofemoral contact forces 10.1 and 19.9% with 15 and 30kg of carried load, respectively, compared to unloaded walking. These results suggest that soldiers carrying loads in excess of 15 kg for prolonged periods could be at greater risk of knee MSI than those with less exposure. [ABSTRACT FROM AUTHOR]