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Kinematics, kinetics and biomechanics of human gait are widely investigated fields of research. The biomechanics of locomotion have been described as characterizing muscle activations and synergistic control, i.e., spatial and temporal patterns of coordinated muscle groups and joints. Both kinematic synergies and muscle synergies have been extracted from locomotion data, showing that in healthy people four–five synergies underlie human locomotion; such synergies are, in general, robust across subjects and might be altered by pathological gait, depending on the severity of the impairment. In this work, for the first time, we apply the mixed matrix factorization algorithm to the locomotion data of 15 healthy participants to extract hybrid kinematic–muscle synergies and show that they allow us to directly link task space variables (i.e., kinematics) to the neural structure of muscle synergies. We show that kinematic–muscle synergies can describe the biomechanics of motion to a better extent than muscle synergies or kinematic synergies alone. Moreover, this study shows that at a functional level, modular control of the lower limb during locomotion is based on an increased number of functional synergies with respect to standard muscle synergies and accounts for different biomechanical roles that each synergy may have within the movement. Kinematic–muscular synergies may have impact in future work for a deeper understanding of modular control and neuro-motor recovery in the medical and rehabilitation fields, as they associate neural and task space variables in the same factorization. Applications include the evaluation of post-stroke, Parkinson's disease and cerebral palsy patients, and for the design and development of robotic devices and exoskeletons during walking. [ABSTRACT FROM AUTHOR]

Purpose: Understanding muscle-tendon forces (e.g., triceps surae and Achilles tendon) during locomotion may aid in the assessment of human performance, injury risk, and rehabilitation progress. Shear wave tensiometry is a noninvasive technique for assessing in vivo tendon forces that has been recently adapted to a wearable technology. However, previous laboratory-based and outdoor tensiometry studies have not evaluated running. This study was undertaken to assess the capacity for shear wave tensiometry to produce valid measures of Achilles tendon loading during running at a range of speeds. Methods: Participants walked (1.34 m⋅s-1) and ran (2.68, 3.35, and 4.47 m⋅s-1) on an instrumented treadmill while shear wave tensiometers recorded Achilles tendon wave speeds simultaneously with whole-body kinematic and ground reaction force data. A simple isometric task allowed for the participant-specific conversion of Achilles tendon wave speeds to forces. Achilles tendon forces were compared with ankle torque measures obtained independently via inverse dynamics analyses. Differences in Achilles tendon wave speed, Achilles tendon force, and ankle torque across walking and running speeds were analyzed with linear mixed-effects models. Results: Achilles tendon wave speed,Achilles tendon force, and ankle torque exhibited similar temporal patterns across the stance phase of walking and running. Significant monotonic increases in peak Achilles tendon wave speed (56.0-83.8 m⋅s-1), Achilles tendon force (44.0-98.7 N⋅kg-1), and ankle torque (1.72-3.68 N⋅m⋅(kg-1)) were observed with increasing locomotion speed (1.34-4.47 m⋅s-1). Tensiometry estimates of peak Achilles tendon force during running (8.2-10.1 body weights) were within the range of those estimated previously via indirect methods. Conclusions: These results set the stage for using tensiometry to evaluate Achilles tendon loading during unobstructed athletic movements, such as running, performed in the field. [ABSTRACT FROM AUTHOR]

An eccentrically lengthening, energy-absorbing, brake-driven model of hamstring function during the late-swing phase of sprinting has been widely touted within the existing literature. In contrast, an isometrically contracting, spring-driven model of hamstring function has recently been proposed. This theory has gained substantial traction within the applied sporting world, influencing understandings of hamstring function while sprinting, as well as the development and adoption of certain types of hamstring-specific exercises. Across the animal kingdom, both spring- and motor-driven muscle–tendon unit (MTU) functioning are frequently observed, with both models of locomotive functioning commonly utilising some degree of active muscle lengthening to draw upon force enhancement mechanisms. However, a method to accurately assess hamstring muscle–tendon functioning when sprinting does not exist. Accordingly, the aims of this review article are three-fold: (1) to comprehensively explore current terminology, theories and models surrounding muscle–tendon functioning during locomotion, (2) to relate these models to potential hamstring function when sprinting by examining a variety of hamstring-specific research and (3) to highlight the importance of developing and utilising evidence-based frameworks to guide hamstring training in athletes required to sprint. Due to the intensity of movement, large musculotendinous stretches and high mechanical loads experienced in the hamstrings when sprinting, it is anticipated that the hamstring MTUs adopt a model of functioning that has some reliance upon active muscle lengthening and muscle actuators during this particular task. However, each individual hamstring MTU is expected to adopt various combinations of spring-, brake- and motor-driven functioning when sprinting, in accordance with their architectural arrangement and activation patterns. Muscle function is intricate and dependent upon complex interactions between musculoskeletal kinematics and kinetics, muscle activation patterns and the neuromechanical regulation of tensions and stiffness, and loads applied by the environment, among other important variables. Accordingly, hamstring function when sprinting is anticipated to be unique to this particular activity. It is therefore proposed that the adoption of hamstring-specific exercises should not be founded on unvalidated claims of replicating hamstring function when sprinting, as has been suggested in the literature. Adaptive benefits may potentially be derived from a range of hamstring-specific exercises that vary in the stimuli they provide. Therefore, a more rigorous approach is to select hamstring-specific exercises based on thoroughly constructed evidence-based frameworks surrounding the specific stimulus provided by the exercise, the accompanying adaptations elicited by the exercise, and the effects of these adaptations on hamstring functioning and injury risk mitigation when sprinting. [ABSTRACT FROM AUTHOR]

Collecting large datasets for investigations into human locomotion is an expensive and labor-intensive process. Methods for 3D human pose estimation in the wild are becoming increasingly accurate and could soon be sufficient to assist with the collection of datasets for analysis into running kinematics from TV broadcast data. In the domain of biomechanical research, small differences in 3D angles play an important role. More precisely, the error margins of the data collection process need to be smaller than the expected variation between athletes. In this work, we propose a method to infer the global geometry of track and field stadium recordings using lane demarcations. By projecting estimated 3D skeletons back into the image using this global geometry, we show that current state-of-the-art 3D human pose estimation methods are not (yet) accurate enough to be used in kinematics research. [ABSTRACT FROM AUTHOR]

Chronic Non-Specific Low Back Pain (cNSLBP) has been identified as one of the leading global causes of disability and is characterized by symptoms without clear patho-anatomical origin. The majority of clinical trials assess cNSLBP using scales or questionnaires, reporting an influence of cognitive, emotional and behavioral factors. However, few studies have explored the effect of chronic pain in daily life tasks such as walking and avoiding obstacles, which involves perceptual-motor processes to interact with the environment. Are action strategies in a horizontal aperture crossing paradigm affected by cNSLBP and which factors influence these decisions ? 15 asymptomatic adults (AA) and 15 cNSLBP participants walked along a 14 m long path, crossing through apertures ranging from 0.9 to 1.8 times their shoulder width. Their movement was measured using the Qualisys system, and pain perception was evaluated by self-administered questionnaires. The cNSLBP participants stopped rotating their shoulders for a smaller aperture relative to their shoulder width (1.18) than the AA participants (1.33). In addition, these participants walked slower, which gave them more time to make the movement adaptations necessary to cross the aperture. No correlation was found between the variables related to pain perception and the critical point but the levels of pain were low with a small variability. This study shows that during a horizontal aperture crossing task requiring shoulder rotation to pass through small apertures, cNSLBP participants appear to exhibit a riskier adaptive strategy than AA participants by minimizing rotations that could induce pain. This task thus makes it possible to discriminate between cNSLBP participants and pain-free participants without measuring the level of pain. The identification number registered in the clinical trials is NCT05337995. • Investigation of cNSLBP movement strategies in an ecological context. • Horizontal aperture crossing paradigm discriminated the influence of cNSLBP. • cNSLBP participants stopped turning their shoulder at a smaller opening. • Pain perception scores were not correlated with the critical point but were low. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine strategies to absorb impact shock during RaceRunning in participants with neurological motor disorders. For this purpose, 8 RaceRunning athletes (4 male and 4 female) voluntarily took part in the study. Each participant performed a series of 100-m sprints with a RaceRunning bike. Acceleration of the tibia and head was measured with 2 inertial measurement units and used to calculate foot-impact shock measures. Results showed that RaceRunning pattern was characterized by a lack of impact peak in foot–ground contact time and the existence of an active peak after foot contact. Due to the ergonomic properties of the RaceRunning bike, shock is attenuated throughout the stance phase. In conclusion, the results revealed that RaceRunning athletes with neurological motor disorders are capable of absorbing impact shock during assisted RaceRunning using a strategy that mimics runners without disabilities. [ABSTRACT FROM AUTHOR]

Humans readily traverse obstacles irrespective of whether they walk or run, despite strong differences between these gaits. Assuming that the control of human obstacle traversal may be either gait-specific or gait-independent, the present study investigates whether previous experience in an obstacle traversal task transfers between the two gaits, and, if this was the case, whether transfer worked both ways. To this end, we conducted a within-group comparison of kinematic adjustments during human obstacle traversal in both walking and running, with distinct participant groups for the two gait sequences. Participants (n = 12/12 (f/m), avg. 25 yo) were motion captured as they traversed obstacles at walking and running speeds on a treadmill, surrounded by an immersive virtual reality (VR) environment. We find that kinematics recorded in our VR setup are consistent with that obtained in real-world experiments. Comparison of learning curves reveals that participants are able to utilize previous experience and transfer learned adjustments from one gait to another. However, this transfer is not symmetrical, with previous experience during running leading to increased success rate in walking, but not the other way round. From a range of step parameters we identified lacking toe height of the trailing leg as the main cause for this asymmetry. [ABSTRACT FROM AUTHOR]

Some works have already studied human trajectories during spontaneous locomotion. However, this topic has not been thoroughly studied in the context of human-human interactions, especially during collaborative carriage tasks. Thus, this manuscript aims to provide a broad analysis of the kinematics of two subjects carrying a table. In the present study, 20 pairs of subjects moved a table to 9 different goal positions distant of 2.7–5.4 m. This was performed with only one or both subjects knowing the target location. The analysis of the collected data demonstrated that there is no shared strategy implemented by all the pairs to move the table around. We observed a great variability in the pairs' behaviours. Even the same pair can implement various strategies to move a table to the same goal position. Moreover, a model of the trajectories adopted by collaborating pairs was proposed and optimized with an inverse optimal control scheme. Even if it produced consistent results, due to the great variability which origins were not elucidated, it was not possible to accurately simulate the average trajectories nor the individual ones. Thus, the approach that was shown to be efficient to simulate single walking subjects failed to model the behaviour of collaborating pairs. [ABSTRACT FROM AUTHOR]

Comprehensive data sets for lower-limb kinematics and kinetics during slope walking and running are important for understanding human locomotion neuromechanics and energetics and may aid the design of wearable robots (e.g., exoskeletons and prostheses). Yet, this information is difficult to obtain and requires expensive experiments with human participants in a gait laboratory. This study thus presents an empirical mathematical model that predicts lower-limb joint kinematics and kinetics during human walking and running as a function of surface gradient and stride cycle percentage. In total, 9 males and 7 females (age: 24.56 ± 3.16 years) walked at a speed of 1.25 m/s at five surface gradients (-15%, -10%, 0%, +10%, +15%) and ran at a speed of 2.25 m/s at five different surface gradients (-10%, -5%, 0%, +5%, +10%). Joint kinematics and kinetics were calculated at each surface gradient. We then used a Fourier series to generate prediction equations for each speed's slope (3 joints x 5 surface gradients x [angle, moment, mechanical power]), where the input was the percentage in the stride cycle. Next, we modeled the change in value of each Fourier series' coefficients as a function of the surface gradient using polynomial regression. This enabled us to model lower-limb joint angle, moment, and power as functions of the slope and as stride cycle percentages. The average adjusted R2 for kinematic and kinetic equations was 0.92 ± 0.18. Lastly, we demonstrated how these equations could be used to generate secondary gait parameters (e.g., joint work) as a function of surface gradients. These equations could be used, for instance, in the design of exoskeletons for walking and running on slopes to produce trajectories for exoskeleton controllers or for educational purposes in gait studies. [ABSTRACT FROM AUTHOR]

Multiple sclerosis can cause locomotor and cognitive impairments even at lower levels of disability, which can impact daily life. The cognitive-motor dual task is commonly used to assess everyday locomotion. Thus, this study aimed to examine the effect of cognitive-motor dual tasks on gait parameters among patients with multiple sclerosis in the early disease stages and to determine whether dual tasks could be used as a clinical test to detect locomotion impairments. A systematic search of five databases was conducted in May 2024. The population of interest was patients with multiple sclerosis with an Expanded Disability Status Scale score of 4 or less. The following outcome measures were examined: spatiotemporal and kinematic parameters. The Newcastle–Ottawa Scale was used to assess the quality of the studies. Eleven studies including 270 patients with multiple sclerosis and 221 healthy controls. Three spatiotemporal parameters were modified both in patients with multiple sclerosis and healthy controls during dual-task performance: gait speed, stride length and the double support phase. No spatiotemporal parameter was affected during dual-task performance in patients with multiple sclerosis alone. Dual-task performance could be useful for assessing gait impairments in patients with multiple sclerosis provided that assessments and protocols are standardized. Nevertheless, the spatiotemporal parameters did not allow discrimination between patients with multiple sclerosis at an early stage and healthy controls. Three-dimensional gait analysis during dual-task performance could be a useful approach for detecting early gait impairments in patients with multiple sclerosis, assessing their progression and adjusting rehabilitation programs. • Three gait parameters were often modified in patients and controls during dual-task. • These parameters are not specific to early gait disorders in multiple sclerosis. • The review highlighted the heterogeneity of clinical, cognitive assessments and tasks. • 3D gait analysis could characterize early gait disorders in multiple sclerosis. [ABSTRACT FROM AUTHOR]

Background: Individuals with locomotive syndrome (LS) require nursing care services owing to problems with locomotion and the musculoskeletal system. Individuals with LS generally have a reduced walking speed compared with those without LS. However, differences in lower-limb kinematics and gait between individuals with and without LS are not fully understood. This study aimed to clarify the characteristics of the gait kinematics of individuals with LS using wearable sensors.Methods: We assessed 125 participants (mean age 73.0 ± 6.7 years) who used a public health promotion facility. Based on the 25-question Geriatric Locomotive Function Scale (GLFS-25), these participants were grouped into the non-LS (GLFS-25 < 7), LS-stage 1 (GLFS-25 7-16), and LS-stage 2 (GLFS-25 ≥ 16) groups (larger GLFS-25 scores indicate worse locomotive ability). Spatiotemporal parameters and lower-limb kinematics during the 10-m walk test were analyzed by the "H-Gait system", which is a motion analysis system that was developed by the authors and is based on seven inertial sensors. The peak joint angles during the stance and swing phases, as well as the gait speed, cadence, and step length were compared among all groups.Results: There were 69 participants in the non-LS group, 33 in the LS-stage 1 group, and 23 in the LS-stage 2 group. Compared with the non-LS group, the LS-stage 2 group showed significantly smaller peak angles of hip extension (9.5 ± 5.3° vs 4.2 ± 8.2°, P = 0.002), hip flexion (34.2 ± 8.8° vs 28.5 ± 9.5°, P = 0.026), and knee flexion (65.2 ± 18.7° vs 50.6 ± 18.5°, P = 0.005). The LS-stage 1 and LS-stage 2 groups had a significantly slower mean gait speed than the non-LS group (non-LS: 1.3 ± 0.2 m/s, LS-stage 1: 1.2 ± 0.2 m/s, LS-stage 2: 1.1 ± 0.2 m/s, P < 0.001).Conclusions: The LS-stage 2 group showed significantly different lower-limb kinematics compared with the non-LS group, including smaller peak angles of hip extension, hip flexion, and knee flexion. It would be useful to assess and improve these small peak joint angles during gait for individuals classified as LS-stage 2. [ABSTRACT FROM AUTHOR]

This study combines metabolic and kinematic measurements at the whole‐body level, with EMG and ultrasound measurements to investigate the influence of muscle‐tendon mechanical behavior on the energy cost (Cnet) of walking (from 2 to 8 km·h−1). Belly gearing (Gb = Δmuscle‐belly length/Δfascicles length) and tendon gearing (Gt = ∆muscle‐tendon unit length/∆muscle‐belly length) of vastus lateralis (VL) and gastrocnemius medialis (GM) were calculated based on ultrasound data. Pendular energy recovery (%R) was calculated based on kinematic data, whereas the cumulative activity per distance travelled (CMAPD) was calculated for the VL, GM, tibialis anterior, and biceps femoris as the ratio between their EMG activity and walking speed. Finally, total CAMPD (CMAPDTOT) was calculated as the sum of the CMAPD of all the investigate muscles. Cnet and CMAPDTOT showed a U‐shaped behavior with a minimum at 4.2 and 4.1 km·h−1, respectively; while %R, VL, and GM belly gearing showed an opposite trend, reaching a maximum (60% ± 5%, 1.1 ± 0.1 and 1.5 ± 0.1, respectively), between 4.7 and 5 km·h−1. Gt was unaffected by speed in GM (3.5 ± 0.1) and decreased as a function of it in VL. A multiple stepwise linear regression indicated that %R has the greatest influence on Cnet, followed by CMAPDTOT and GM belly gearing. The role of Gb on Cnet could be attributed to its role in determining muscle work: when Gb increases, fascicles shortening decreases compared with that of the muscle‐belly, thereby reducing the energy cost of contraction. [ABSTRACT FROM AUTHOR]

Locomotion in animals provides a model for adaptive behavior as it is able to deal with various kinds of perturbations. Work in insects suggests that this evolved flexibility results from a modular architecture, which can be characterized by a recurrent neural network allowing for various emerging attractor states. Whereas a lower control-level coordinates joint movements on a short timescale, a higher-level handles action selection on longer timescales. Implementation of such a control system on a walking hexapod robot was able to deal with various walking patterns including disturbances such as uneven terrain or loss of a leg. Here, we propose a cognitive expansion to the adaptive control system that allows dealing with novel challenging situations. This approach makes use of an internal simulation-based planner that is triggered when the model-free controller fails to recover from an unstable pose. Using a grounded internal body model, the planner then tries, in internal simulation, different solutions out of context, and thus, proposes a new plan to be executed on the real robot. We demonstrate the feasibility of this control approach for walking over terrain with uncertain footholds in three scenarios. [ABSTRACT FROM AUTHOR]

We developed and validated a multi-segment foot and ankle model for human walking and running. The model has 6-segments, and 7 degrees of freedom; motion between foot segments were constrained with a single oblique axis to enable triplanar motion [Joint Constrained (JC) model]. The accuracy of the JC model and that of a conventional model using a 6 degrees of freedom approach were assessed by comparison to segment motion determined with biplanar videoradiography. Compared to the 6-DoF model, our JC model demonstrated significantly smaller RMS differences [JC: 2.19° (1.43–2.73); 6-DoF: 3.25° (1.37–5.89)] across walking and running. The JC model is thus capable of more accurate musculoskeletal analyses and is also well suited for predictive simulations. [ABSTRACT FROM AUTHOR]

Background: Individuals experiencing age-related decline in locomotor functions are at high-risk of developing locomotive syndrome (LS). LS requires long-term care and greatly influences the quality of life and activities of daily living. The LS risk test was established as a diagnostic criterion by the Japanese Orthopedic Association. Although the relationship between the test and motor function has been established, few studies have reported on the characteristics of LS kinematically and kinetically.Research Question: Do elderly with LS show different kinetic and kinematic characteristics compared with healthy elderly during static standing and level walking?Methods: Forty-four Participants were divided into an LS group and a non-LS group based on the scores of the LS risk test. The standing posture and walking of the participants were measured using a three-dimensional motion capture system. The results of the groups were compared using an unpaired t-test, and then the characteristics of the LS group were extracted using logistic regression analysis.Results: LS group exhibited trunk flexion during both standing and gait. A higher intervertebral disc compressive force, which is the index of the low-back mechanical stress, during standing and an increase in ankle plantarflexion angle during walking were observed in LS group.Significance: This study determined the kinematic and kinetic features of elderly with LS. The findings suggest that parameters related to the trunk and ankle could be associated with LS. Further studying the characteristics of LS in older adults via motion analysis can help develop prevention and intervention methods for LS. [ABSTRACT FROM AUTHOR]

Salamanders are often used as a model of early tetrapod locomotion, due to their generalized tetrapod body plan. We imaged five individuals of wandering salamander, Aneides vagrans, during horizontal and vertical locomotion and compared kinematic and gait adjustments made to compensate for each condition. We used ImageJ to calculate duty factor, stride length, stride frequency, contralateral foot spread, heading of climbing, and forward velocity. Like other terrestrial salamanders, A. vagrans use a diagonal couplet, lateral sequence walk on horizontal surfaces. When walking vertically, however, they use a single‐foot gait, taking smaller steps and extending the duty factor compared with level walking. Salamanders adjusted their limbs to have a wider contralateral foot spread between fore‐ and hindfeet when walking downward as compared to walking upward or horizontally. These gait adjustments may minimize the risk of slipping or falling by increasing the number of contact points during the stride cycle, and by bringing their center of mass closer to the surface. We found that salamanders moved at a significantly faster velocity when traveling horizontally compared to vertically. Furthermore, we found no significant difference between upward and downward velocity, despite greater stride lengths in upward locomotion; this was explained by a higher stride frequency in downward locomotion. We estimate travel time up or down an old‐growth redwood tree to be on the scale of hours, a significant time investment that may encourage alternatives when available. These results suggest that, in an ecological context, while salamanders are capable of traveling straight down a redwood tree, they may simply tend to jump. [ABSTRACT FROM AUTHOR]

The current investigation examined muscle-tendon unit kinematics and kinetics in human participants asked to perform a hopping task for maximal performance with variational preceding milieu. Twenty-four participants were allocated post-data collection into those participants with an average hop height of higher (HH) or lower (LH) than 0.1 m. Participants were placed on a customized sled at a 20º angle while standing on a force plate. Participants used their dominant ankle for all testing and their knee was immobilized and thus all movement involved only the ankle joint and corresponding propulsive unit (triceps surae muscle complex). Participants were asked to perform a maximal effort during a single dynamic countermovement hop (CMH) and drop hops from 10 cm (DH10) and 50 cm (DH50). Three-dimensional motion analysis was performed by utilizing an infrared camera VICON motion analysis system and a corresponding force plate. An ultrasound probe was placed on the triceps surae muscle complex for muscle fascicle imaging. HH hopped significantly higher in all hopping tasks in comparison to LH. In addition, the HH group concentric ankle work was significantly higher in comparison to LH during all of the hopping tasks. Active muscle work was significantly higher in HH in comparison to LH as well. Tendon work was not significantly different between HH and LH. Active muscle work was significantly correlated with hopping height (r = 0.97) across both groups and hopping tasks and contributed more than 50% of the total work. The data indicates that humans primarily use a motor-driven system and thus it is concluded that muscle actuators and not springs maximize performance in hopping locomotor tasks in humans. [ABSTRACT FROM AUTHOR]

Background: Adaptation of the walking pattern to uphill walking demands immediate coordination between the lower limb segments. Nonetheless, knowledge about individual joints' responses and variability in response to the new slope angles are missing.Aims: This study investigated the impacts of uphill walking on the ankle, the knee and the hip joints angles and their variability.Methods: Twenty-three collegiate athletes (age: 22.04 ± 3.43years, body mass: 62.14 ± 9.26Kg, height: 168.29 ± 7.06 cm) walked on an inclined treadmill at 0 ° (level walking -LW), 5 ° (low-slope-walking -LSW), and 10 ° (high-slope-walking -HSW) slopes at their preferred walking speed (4.2 ± 0.51 km.h-1). The ankle, knee and hip joints angles and their variability (standard deviations) were calculated and analysed throughout the gait cycles in LW, LSW, and HSW.Results: Repeated measure ANOVA portrayed significant differences between the ankle joint angles in sagittal (p < .001, ηp2>.14), frontal (p < .05, ηp2>.14), and transverse (p < .005, .14 < ηp2>.01) planes. In the knee joint, the sagittal (p < .001, ηp2>.14), frontal (p < .05, ηp2>.14), and transverse (p < .05, ηp2>.14) angles were significantly different (p < 0.05). Similarly, in the hip joint, the sagittal (p < .05, ηp2>.14), frontal (p < .05, ηp2>.14), and transverse (p < .05, ηp2>.14) angles were significantly different. Ankle angle variability was significantly different in sagittal (P < .001, ηp2>.14), frontal (p = .002, ηp2>.14) and horizontal (P < .001, ηp2>.14) planes, as well as knee joint angle variability in sagittal, frontal and horizontal planes p < 0.001, ηp2>.14. The hip joint variability was considerably different in sagittal (p = .031, ηp2>.14) and horizontal (p < .05, ηp2>.14) planes.Conclusion: Uphill walking involves further modifications in the ankle, knee and hip joints angle to adjust the whole-body movements to a new slope. This adjustment resulted in a firm base of support, provided by the ankle, to regulate the knee and hip joints modifications. Nevertheless, it caused less ankle movement variability and could end up with injuries over long-term uphill walking. [ABSTRACT FROM AUTHOR]

Background: Control of dynamic balance in human walking is essential to remain stable and can be parameterized by the margins of stability. While frontal and sagittal plane margins of stability are often studied in parallel, they may covary, where increased stability in one plane could lead to decreased stability in the other. Hypothetically, this negative covariation may lead to critically low lateral stability during step lengthening.Research Question: Is there a relationship between frontal and sagittal plane margins of stability in able-bodied humans, during normal walking and imposed step lengthening?Methods: Fifteen able-bodied adults walked on an instrumented treadmill in a normal walking and a step lengthening condition. During step lengthening, stepping targets were projected onto the treadmill in front of the participant to impose longer step lengths. Covariation between frontal and sagittal plane margins of stability was assessed with linear mixed-effects models for normal walking and step lengthening separately.Results: We found a negative covariation between frontal and sagittal plane margins of stability during normal walking, but not during step lengthening.Significance: These results indicate that while a decrease in anterior instability may lead to a decrease in lateral stability during normal walking, able-bodied humans can prevent lateral instability due to this covariation in critical situations, such as step lengthening. These findings improve our understanding of adaptive dynamic balance control during walking in able-bodied humans and may be utilized in further research on gait stability in pathological and aging populations. [ABSTRACT FROM AUTHOR]

Background: Previous work has linked the eccentricity of the net ground reaction force (GRFnet) to increased mediolateral instability during single-step voluntary and compensatory stepping responses. The present work sought to understand the extent to which such control mechanisms for mediolateral stability are present during gait.Research Question: How do gait velocity and step width constraints influence the kinetic control of mediolateral stability control among healthy participants?Methods: 25 participants performed three walking conditions - normal walking with self-selected speed and foot-placement, fast walking with self-selected foot-placement, and narrowbase walking - across a 10-meter walkway. Lateral instability was quantified by the mediolateral margin of stability (MoSML). The frontal-plane eccentricity of the GRFnet was calculated as the difference between GRFnet vector orientation and that of a line joining the coordinates of COPnet and COM. Two discrete time-points (P1 and P2) following foot-contact were examined, as they have been suggested to be indicative of proactive and reactive COM control, respectively. Task-related differences in the magnitude and timing of kinematic and kinetic outcome variables were analysed using one-way ANOVAs with repeated-measures.Results: With constraints on step-width in narrow-base walking, participants exhibited reduced stability as evidenced by reduced MoSML, alongside reductions in the peak GRFnet eccentricity (θd) at P1. Participants exhibited no reduction in stability during fast walking, as revealed by the MoSML in part because of a similar onset of P1 within the gait cycle. P2 magnitude was larger in narrow-base walking relative to fast-walking, and occurred at an earlier point in the gait cycle.Significance: Findings suggest proactive mechanisms (i.e. P1) may predominantly regulate mediolateral stability during walking. Reactive mechanisms (i.e. P2), however, may be capable of offsetting instability in situations where proactive mechanisms are insufficient. [ABSTRACT FROM AUTHOR]

The kinematics of the body center of mass (bCoM) may provide crucial information supporting the rehabilitation process of people with transfemoral amputation. The use of magneto-inertial measurement units (MIMUs) is promising as it may allow in-the-field bCoM motion monitoring. Indeed, bCoM acceleration might be obtained by fusing the estimated accelerations of body segments' centers of mass (sCoM), the formers being computed from the measured accelerations by segment-mounted MIMUs and the known relative position between each pair of MIMU and underlying sCoM. This paper investigates how erroneous identifications of MIMUs positions impact the accuracy of estimated 3D sCoM and bCoM accelerations in transfemoral amputee gait. Using an experimental design approach, 215 simulations of erroneous identifications of MIMUs positions (up to 0.02 m in each direction) were simulated over seven recorded gait cycles of one participant. MIMUs located on the trunk and sound lower limbs were shown to explain up to 77% of the variance in the accuracy of the estimated bCoM acceleration, presumably due to the higher mass and/or angular velocity of these segments during gait of lower-limb amputees. Therefore, a special attention should be paid when identifying the positions of MIMUs located on segments contributing the most to the investigated motion. Sensitivity of the estimated vertical body center of mass acceleration to erroneous identifications of MIMU positions in the anteroposterior (AP), mediolateral (ML), and vertical (V) directions, expressed in percentage of the total variance of the estimation accuracy. [ABSTRACT FROM AUTHOR]

The compliant nature of distal limb muscle‐tendon units is traditionally considered suboptimal in explosive movements when positive joint work is required. However, during accelerative running, ankle joint net mechanical work is positive. Therefore, this study aims to investigate how plantar flexor muscle‐tendon behavior is modulated during fast accelerations. Eleven female sprinters performed maximum sprint accelerations from starting blocks, while gastrocnemius muscle fascicle lengths were estimated using ultrasonography. We combined motion analysis and ground reaction force measurements to assess lower limb joint kinematics and kinetics, and to estimate gastrocnemius muscle‐tendon unit length during the first two acceleration steps. Outcome variables were resampled to the stance phase and averaged across three to five trials. Relevant scalars were extracted and analyzed using one‐sample and two‐sample t‐tests, and vector trajectories were compared using statistical parametric mapping. We found that an uncoupling of muscle fascicle behavior from muscle‐tendon unit behavior is effectively used to produce net positive mechanical work at the joint during maximum sprint acceleration. Muscle fascicles shortened throughout the first and second steps, while shortening occurred earlier during the first step, where negative joint work was lower compared with the second step. Elastic strain energy may be stored during dorsiflexion after touchdown since fascicles did not lengthen at the same time to dissipate energy. Thus, net positive work generation is accommodated by the reuse of elastic strain energy along with positive gastrocnemius fascicle work. Our results show a mechanism of how muscles with high in‐series compliance can contribute to net positive joint work. [ABSTRACT FROM AUTHOR]

Background: Dysfunction in peripheral and neural structure with spastic cerebral palsy (CP) causes impaired performance and stability of various behaviors. Recent progress of quantification methods for the stability properties, which is based on the uncontrolled manifold hypothesis, has been applied to various neurological disorders. A prior study revealed that the ability for purposeful regulation of stability properties is weakened with CP during finger and hand actions. Successive regulation of stability properties is crucial for human locomotion; therefore, it is imperative to quantify the changes in the intersegmental coordination as to the stable performance in CP individuals during gait.Research Question: We hypothesized that (1) Spastic CP group will show smaller step length and gait velocity with larger variability, and (2) Spastic CP group will show no changes in average stability indices for both the COM and head position stabilization, while the smaller difference between stable and unstable posture during the gait cycle.Methods: Whole-body kinematic data during walking were collected from CP and control subjects. Step length, velocity, and coefficient of variation (CV) were calculated as spatiotemporal parameters. We quantified the intersegmental stability index in time-series during gait for the stabilization of the whole-body COM and head position.Results: The CP subjects showed smaller step length and velocity with larger CV than the controls. However, the CP group showed a significantly less difference in the stability indices between the single- and double-limb support phases as compared to the controls for both the COM and head position stabilization.Significance: Present study is the first to document the quantification of changing intersegmental stability in the spastic CP during locomotion. The dysfunction of intentional modulation of stability properties in CP individuals may be a more common problem, which is not limited to a specific body effector. [ABSTRACT FROM AUTHOR]

Lower limb amputation does not affect only physical and psychological functioning but the use of a prosthetic device can also lead to increased cognitive demands. Measuring cognitive load objectively is challenging, and therefore, most studies use questionnaires that are easy to apply but can suffer from subjective bias. Motivated by this, the present study investigated whether a mobile eye tracker can be used to objectively measure cognitive load by monitoring gaze behavior during a set of motor tasks. Five prosthetic users and eight able-bodied controls participated in this study. Eye tracking data and kinematics were recorded during a set of motor tasks (level ground walking, walking on uneven terrain, obstacle avoidance, stairs up and ramp down, as well as ramp up and stairs down) while the participants were asked to focus their gaze on a visual target for as long as possible. Target fixation times and increase in pupil diameters were determined and correlated to subjective ratings of cognitive load. Overall, target fixation time and pupil diameter showed strong negative and positive correlations, respectively, to the subjective rating of cognitive load in the able-bodied controls (−0.75 and 0.80, respectively). However, the individual correlation strength, and in some cases, even the sign, was different across participants. A similar trend could be observed in prosthetic users. The results of this study showed that a mobile eye tracker may be used to estimate cognitive load in prosthesis users during locomotor tasks. This paves the way to establish a new approach to assessing cognitive load, which is objective and yet practical and simple to administer. Nevertheless, future studies should corroborate these results by comparing them to other objective measures as well as focus on translating the proposed approach outside of a laboratory. • Eye-tracking can provide objective measures of cognitive load for lower limb prosthetic users. • Target fixation time and pupil diameter correlate with subjective ratings of cognitive load. • The strength of the correlation between the eye tracking measures and cognitive load is, however, subject-specific. • This work can lead to a practical and simple way to assess the cognitive load, both inside and outside the lab. [ABSTRACT FROM AUTHOR]

Background: To navigate through dynamically changing environments and to avoid collisions with stationary and moving obstacles, older adults tend to over rely on their visual system because it is a more reliable source of information. Aging affects both visuomotor integration and visual perception, often resulting in the inability to produce appropriate adaptive locomotor actions in a timely manner.Research Question: Does peripheral visual information in the environment affected older adults' ability to complete a gap-crossing task with a set of closing doors at different rates (0.6-1.2 m/s)?Methods: Fifteen older adults (65-74 years) completed the study inside a virtual environment with three different levels of peripheral visual information: 1) empty; 2) stationary avatars; and 3) moving avatars. Kinematic data was collected using an Optotrak camera system to track the older adults' body movements during the task.Results: The results demonstrated that regardless of the environment or closing door speed, older adults maintained consistent approach speeds. However, older adults collided with the fastest moving doors a significant number of times at the fastest door closing rates for the empty and moving avatar conditions.Significance: Although it appears that older adults are able to attend on a central task (i.e., passing through closing doors) and maintain constant behaviours regardless of the visual information from peripheral environment, richness of the peripheral environment provides accurate feedback about self-motion affects success rates. [ABSTRACT FROM AUTHOR]

Background: The initiation in human locomotion is defined as the transition between upright stance and steady-state gait. While past literature abundantly investigated the initiation in bipedal gait, the initiation of handstand walking remains unexplored.Research Question: The current study aims to characterise the centre of pressure (CoP) and centre of mass (CoM) trajectory of handstand walking initiation as well as the spatiotemporal and kinematic parameters and balance strategy of this task. Also, the study examined the CoP trajectory similarity within- and between-participants using a coefficient of multiple correlation analysis.Methods: Nineteen gymnasts took part in this study. Handstand walking initiation trials were recorded using force plates and a stereophotogrammetric system. CoM and CoP trajectories were analysed during the Baseline, Preparation and Execution phases of the motor task.Results: We found that to successfully perform the handstand walking initiation, a shift of the CoM forward and towards the stance hand is required as a result of a lateral and posterior CoP shift. All participants performed a similar CoP pattern in the mediolateral direction, whereas two anteroposterior CoP displacement strategies were identified across participants based on different timing execution of posterior CoP shift. While CoP and CoM kinematic differences were identified during the Preparation Phase due to the adopted strategy, no significant difference was found in the Execution Phase for the spatiotemporal and kinematic characteristics.Significance: A better understanding of the required CoP/CoM patterns and balance control provides the basis for further neuromechanics research on the topic and could contribute to individualise training protocols to improve the learning of the task. [ABSTRACT FROM AUTHOR]

Background: The walk-to-run transition, which occurs during gradually increasing locomotion speed, has been addressed in research at least eight decades back.Research Question: Why does the walk-to-run transition occur? In the present review, we focus on the reason for the transition, more than on the consequences of it. The latter has historically constituted a primary focus.Methods: In the present review, we scrutinize related literature.Results: We present a unifying conceptual framework of the dynamics of human locomotion. The framework unifies observations of the human walk-to-run transition for providing a common understanding. Further, the framework includes a schematic representation of the dynamic interaction between entities of subsystems of the human body during locomotion and the physical environment. We propose that the moving human body can behave as a dynamic non-linear complex system, which basically functions in a self-organized fashion during locomotion. Further, that the stride rate plays a particular key role for the transition. Finally, we propose that the coincidence between attractor stability and minimum energy turnover during locomotion is a consequence of the evolution of the phenotype of the adult human body and the dynamics of the acute process of self-organization during locomotion.Significance: The novel insight from the present work contributes to the academic understanding of human locomotion, including in particular the central behavioural phenomenon of walk-to-run transition. Furthermore, the understanding is relevant for the ongoing work within for example locomotion rehabilitation and development of assistive devices. Regarding the latter, examples could be devices within neurorobotics and exoskeletons where the basic understanding of human locomotion increases the possibility of a successful combination of human and technology. [ABSTRACT FROM AUTHOR]

Computational modelling is an invaluable tool for investigating features of human locomotion and motor control which cannot be measured except through invasive techniques. Recent research has focussed on creating personalised musculoskeletal models using population-based morphing or directly from medical imaging. Although progress has been made, robust definition of two critical model parameters remains challenging: (1) complete tibiofemoral (TF) and patellofemoral (PF) joint motions, and (2) muscle tendon unit (MTU) pathways and kinematics (i.e. lengths and moment arms). The aim of this study was to develop an automated framework, using population-based morphing approaches to create personalised musculoskeletal models, consisting of personalised bone geometries, TF and PF joint mechanisms, and MTU pathways and kinematics. Informed from medical imaging, personalised rigid body TF and PF joint mechanisms were created. Using atlas- and optimisation-based methods, personalised MTU pathways and kinematics were created with the aim of preventing MTU penetration into bones and achieving smooth MTU kinematics that follow patterns from existing literature. This framework was integrated into the Musculoskeletal Atlas Project Client software package to create and optimise models for 6 participants with incrementally increasing levels of personalisation with the aim of improving MTU kinematics and pathways. Three comparisons were made: (1) non-optimised (Model 1) and optimised models (Model 3) with generic joint mechanisms; (2) non-optimised (Model 2) and optimised models (Model 4) with personalised joint mechanisms; and (3) both optimised models (Model 3 and 4). Following optimisation, improvements were consistently shown in pattern similarity to cadaveric data in comparison (1) and (2). For comparison (3), a number of comparisons showed no significant difference between the two compared models. Importantly, optimisation did not produce statistically significantly worse results in any case. [ABSTRACT FROM AUTHOR]

Background: The use of virtual reality (VR) in clinical settings has increased with the introduction of affordable, easy-to-use head-mounted displays (HMDs). However, some have raised concerns about the effects that HMDs have on posture and locomotion, even without the projection of a virtual scene, which may be different across ages.Research Question: How does HMD wear impact the kinematic measures in younger and older adults?Methods: Twelve healthy young and sixteen older adults participated in two testing conditions: 1) TUG with no HMD and 2) TUG with an HMD displaying a scene of the actual environment (TUGHMD). The dependent variables were the pitch, yaw, and roll peak trunk velocities (PTVs) in each TUG component, turning cadence, and the time to complete the TUG and its components - SIT-TO-STAND, TURN, WALK, and STAND-TO-SIT.Results: Wearing the HMD decreased turning cadence and pitch and yaw PTVs in all TUG components, decreased roll PTV in SIT-TO-STAND and TURN, and increased the time taken to complete all TUG components in all participants. Wearing the HMD decreased the pitch PTV in SIT-TO-STAND in older relative to younger adults. Wearing an HMD affected TUG performance in younger and older adults, which should be considered when an HMD is used for VR applications in rehabilitation.Significance: Our findings highlight the importance of considering the physical effect of HMD wear in clinical testing, which may not be present with non-wearable VR technologies. [ABSTRACT FROM AUTHOR]

Supplemental digital content is available in the text. When cyclists ride off the saddle, their center of mass (CoM) appears to go through a rhythmic vertical oscillation during each crank cycle. Just like in walking and running, the pattern of CoM movement may have a significant effect on the mechanical power that needs to be generated and dissipated by muscle. Purpose: To date, neither the CoM movement strategies during nonseated cycling nor the limb mechanics that allow this phenomenon to occur have been quantified. Methods: Here we estimate how much power can be contributed by a rider's CoM at each instant during the crank cycle by combining a kinematic and kinetic approach to measure CoM movement and joint powers of 15 participants riding in a nonseated posture at three individualized power outputs (10%, 30%, and 50% of peak maximal power) and two different cadences (70 and 120 rpm). Results: The peak-to-peak amplitude of vertical CoM displacement increased significantly with power output and with decreasing cadence. Accordingly, the greatest peak-to-peak amplitude of CoM displacement (0.06 ± 0.01 m) and change in total mechanical energy (0.54 ± 0.12 J·kg−1) occurred under the combination of high-power output and low cadence. At the same combination of high-power output and low cadence, we found that the peak rate of CoM energy loss (3.87 ± 0.93 W·kg−1) was equal to 18% of the peak crank power. Conclusion: Consequently, it appears that for a given power output, changes in CoM energy contribute to peak instantaneous power output at the crank, thus reducing the required muscular contribution. These findings suggest that the rise and fall of a rider's CoM acts as a mechanical amplifier during nonseated cycling, which has important implications for both rider and bicycle performance. [ABSTRACT FROM AUTHOR]

Background: Clinicians and footwear manufacturers often advise young children to wear soft-soled footwear when they are first learning to walk. There is limited evidence as to why this advice is given, and if soft-soled shoes are as close to barefoot as thought.Research Question: What are the differences in spatiotemporal measures of gait during walking and running in three common types of children's footwear with a soft-soled compared to barefoot in young children?Methods: The study used a quasi-experimental design, with the condition order randomised using a Latin square sequence. Forty-seven children were recruited (2 - 4 years). Participants walked or ran the length of a GAITrite mat in a randomized order for barefoot and soft-soled sneaker, boot and sandal conditions. Linear regression analyses were used to investigate the main effect of each soft-soled footwear compared to bare feet in the different gait parameters.Results: For walking and running trials, cadence decreased whereas step time and stride length increased in all footwear types compared to the barefoot condition. While wearing sneakers and sandals increased the stance percentage for walking and running trials, compared to barefoot, this difference was only apparent during the running trial for the boots. Likewise, although double support time increased for both the boots and sneakers in walking and running, compared to barefoot, this difference was only observed in the sandals during walking.Significance: This research found that various types of soft-soled footwear impacted gait compared to the barefoot condition, with some differences seen between walking and running trials. These findings challenge the assumption that soft-soled footwear facilitate a similar gait to barefoot walking and running, although the clinical significance of these differences is unknown. [ABSTRACT FROM AUTHOR]

Background: High-heeled shoes are currently preferred by women due to contemporary aesthetics. However, high-heeled shoes may increase the effort required to ascend stairs and, hence, alter biomechanical performance.Research Question: How do high-heel shoe parameters affect the pelvis position, lower extremities kinematics, and ground reaction force in young women during stair ascent motion?Methods: Stair ascent experiments were performed with 20 healthy adult women. The participants were instructed to ascend a 3-step staircase, wearing heeled shoes of different heel heights and heel types and one pair of flat shoes as the control group. Changes in lower body biomechanics were analyzed with kinematics and ground reaction force variables collected from the dominant limb. A two-way repeated ANOVA was performed to determine which variables were affected by heel type and which were affected by heel height or a combination of both.Results: As the heel height increased, an increased range of ankle dorsiflexion-plantarflexion, as well as pelvic rotation, was observed(P = 0.039 and P = 0.003, respectively). A thinner heel type displayed a larger pelvic forward tilt movement(P = 0.026)and 1st peak vertical force(P = 0.025), as well as a smaller 2nd peak vertical force (P = 0.002). With high heels, increased external rotation of the knee, inversion and plantar flexion, and flexion values of the knee were observed. We also observed decreased external rotation of the pelvis, ankle eversion, varum, and dorsiflexion.Significance: To stabilize body posture during stair ascent motion with high-heeled shoes, compensatory response including increasd pelvic range of motion and changing the joint angles of the lower extremities. [ABSTRACT FROM AUTHOR]

The Test of Gross Motor Development 2 (TGMD-2) is currently the standard approach for assessing fundamental movement skills (FMS), including locomotor and object control skills. However, its extensive application is restricted by its low efficiency and requirement of expert training for large-scale evaluations. This study evaluated the accuracy of a newly-developed video-based classification system (VCS) with a marker-less sensor to assess children's locomotor skills. A total of 203 typically-developing children aged three to eight years executed six locomotor skills, following the TGMD-2 guidelines. A Kinect v2 sensor was used to capture their activities, and videos were recorded for further evaluation by a trained rater. A series of computational-kinematic-based algorithms was developed for instant performance rating. The VCS exhibited moderate-to-very good levels of agreement with the rater, ranging from 66.1% to 87.5%, for each skill, and 72.4% for descriptive ratings. Paired t-test revealed that there were no significant differences, but significant positive correlation, between the standard scores determined by the two approaches. Tukey mean difference plot suggested there was no bias, with a mean difference (SD) of -0.16 (1.8) and respective 95% confidence interval of 3.5. The kappa agreement for the descriptive ratings between the two approaches was found to be moderate (k = 0.54, p < 0.01). Overall, the results suggest the VCS could potentially be an alternative to the conventional TGMD-2 assessment approach for assessing children's locomotor skills without the necessity of the presence of an experienced rater for the administration. [ABSTRACT FROM AUTHOR]

Background: A lack of movement coordination characterized by the undershoot or overshoot of the intended location with the hand, arm, or leg is often found in individuals with multiple sclerosis (MS). Standardized as Finger-to-Nose (FNT) and The Heel-to-Shin (HST) tests are the most frequently used tests for qualitative examination of upper and lower body coordination. Inertial sensors facilitate in performing quantitative motion analysis and by estimating body symmetry more accurately assess coordination lesion and imbalance.Objectives: To assess the body symmetry of upper and lower limbs quantitatively, and to find the best body symmetry indices to discriminate MS from healthy individuals (CO).Methods: 28 MS patients and 23 CO participated in the study. Spatiotemporal parameters obtained from six Inertial Measurement Units (IMUs) were placed on the upper and lower extremities during FNT and HST tests. All data were analyzed using statistical methods in MATLAB.Results: Asymmetry indices of temporal parameters showed a significant increase in upper body and lower body asymmetry of MS compared to CO. However, CO have a greater kinematic asymmetry compared to MS.Conclusion: Temporal parameters are the most sensitive to body asymmetry evaluation. However, range of motion is completely inappropriate if it is calculated for one movement cycle. [ABSTRACT FROM AUTHOR]

Background: During everyday locomotion, we cope with various internal or external perturbations (e.g. uneven surface). Uncertainty exists on how unpredictable external perturbations increase noise within the motor system and if they are compensated by employing covariation of the limb joints or rather due to decreased sensitivity of an altered posture.Research Question: Do continuous stochastic perturbations affect the structure of gait variability in young and healthy adults?Methods: In a cross-over study, gait kinematics of 21 healthy young sports students were registered during treadmill walking with and without continuous stochastic perturbations. Using the TNC method, the following aspects were analyzed: (a) the sensitivity of body posture to perturbations ('tolerance') decreasing gait variability, (b) the unstructured motor 'noise' increasing gait variability and (c) the amount of 'covariation' of the limb joints.Results: Compared to normal walking, gait variability was significantly increased (p < .001) during walking with perturbations. The negative effect of noise was partly compensated by improved 'covariation' of leg joints (p < .001). The aspect 'tolerance' had a small effect on increasing gait variability during stance phase (p < .001) and decreasing gait variability during swing phase (p < .001).Significance: Increased motor noise due to external perturbations is partly compensated by improved covariation of the limb joints. However, the effect of an altered posture slightly affects gait variability. Further studies should focus on different populations (e.g. older participants) to see if they use the same mechanism (improved covariation) to compensate for stochastic perturbations. [ABSTRACT FROM AUTHOR]

Background: Control of body orientation requires head motion detection by the vestibular system and small changes with respect to the gravitational acceleration vector could cause destabilization.Research Question: We aimed to compare the effects of different head orientations on gait stability in young adults, dancers and older adults.Methods: Three groups of 10 subjects were evaluated, the first composed of young adults (aged 18-30 years), the second composed of young healthy dancers under high performance dance training (aged 18-30 years), and the third group composed of community-dwelling older adults (aged 65-80 years). Participants walked on a treadmill at their preferred speed in four distinct head orientation conditions for four minutes each: control (neutral orientation); dynamic yaw (following a target over 45° bilaterally); up (15° neck extension), and down (40° neck flexion). Foot and trunk kinematic data were acquired using a 3D motion capture system and the gait pattern was assessed by basic gait parameters (step length, stride width and corresponding variability) and gait stability (local divergence exponents and margins of stability). Main effects of conditions and groups, as well as their interaction effects, were evaluated by repeated-measures analysis of variance.Results: Interactions of group and head orientation were found for both step length and stride width variability; main effects of head orientation were found for all evaluated parameters and main effects of group were found for step length and its variability and local divergence exponents in all directions.Significance: As expected, the older adults group showed less stable gait (higher local divergence exponent), the shortest step length and greater step length variability. However, contrary to expectation, the dancers were not more stable. The yaw condition was the most challenging for all groups and the down condition seemed to be least challenging. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to investigate the influence of walking speed on the pendular mechanism, cost of transport, mechanical efficiency and mechanical work in adults with lower-limb amputation, compared to a control group. Methods: Observational, cross sectional study. Ten subjects from an amputee rehabilitation clinic, with the same prosthetic knee and foot and ten healthy subjects were selected to form the experimental and the control group, respectively. Tridimensional kinematics data and oxygen uptake were collected simultaneously at five speeds: the self-selected walking speed (SSWS), two speeds above and below. Results: In the experimental group, the cost of transport was higher than in controls. Contrary to controls, in experimental group the minimum cost of transport and the maximum recovery did not coincide to the SSWS, but were reached at the maximum speed of the protocol. The mechanical efficiency in experimental group was lower, while the external mechanical work and pendular transduction were higher than in controls. Conclusions: The clinical relevance of these results is the concept, also supported by other studies, that interventions headed to increase the SSWS in the experimental group also increase and optimise the energetic economy and the pendulum efficiency of their locomotion. [ABSTRACT FROM AUTHOR]

Background: In the three-dimensional kinematic analysis of the trunk during human locomotion, a multi-segmental rigid-body model would be a better representation for the trunk compared with a single rigid-body model with regard to goodness-of-fit. However, there is a trade-off between data fitting and the simplicity of the model.Research Question: This study aimed to determine the optimal number of rigid-body segments during walking and running using Akaike's information criterion (AIC), which determines the model that has goodness-of-fit and is generalizable.Methods: Empirically obtained kinematic data for the trunk during walking and running were fitted by one-, two-, three-, and six-linked rigid-body models using a nonlinear optimization algorithm. The relative quality of these models was assessed using their bias-corrected AIC (AICc) value.Results: The AICc values of two- and three-linked rigid-body models were significantly smaller than those of one- or six-segment models for the walking trial. For the running trial, the AICc values of two-, three-, and six-segment models were significantly smaller than that of the single rigid-body model.Discussion: These results suggest that both two- and three-linked rigid-body models would be better than the one- and six-linked rigid-body representations for analyzing trunk movement during walking, whereas the two-, three-, and six-linked models would be comparably well-balanced models in terms of both the goodness-of-fit and generalizability for running analysis. [ABSTRACT FROM AUTHOR]

Background: Hip external rotation stiffness, midfoot passive mechanical resistance and foot alignment may influence on ankle, knee and hip movement in the frontal and transverse planes during gait.Research Question: Are hip stiffness, midfoot mechanical resistance and foot alignment associated with ankle, knee and hip kinematics during gait?Methods: Hip stiffness, midfoot mechanical resistance, and foot alignment of thirty healthy participants (18 females and 12 males) with average age of 25.4 years were measured. In addition, lower limb kinematic data during the stance phase of gait were collected with the Qualisys System (Oqus 7+). Stepwise multiple linear regressions were performed to identify if hip stiffness, midfoot torque, midfoot stiffness and foot alignment were associated with hip and knee movement in the transverse plane and ankle movement in the frontal plane with α = 0.05.Results: Reduced midfoot torque was associated with higher hip range of motion (ROM) in the transverse plane (r2 = 0.18), reduced hip stiffness was associated with higher peak hip internal rotation (r2 = 0.16) and higher ROM in the frontal plane (r2 = 0.14), reduced midfoot stiffness was associated with higher peak knee internal rotation (r2 = 0.14) and increased midfoot torque and midfoot stiffness were associated with higher peak knee external rotation (r2 = 0.36).Significance: These findings demonstrated that individuals with reduced hip and midfoot stiffness have higher hip and knee internal rotation and higher ankle eversion during the stance phase of gait. On the other hand, individuals with increased midfoot torque and stiffness have higher knee external rotation. These relationships can be explained by the coupling between ankle movements in the frontal plane and knee and hip movements in the transverse plane. Finally, this study suggests that midfoot passive mechanical resistance and hip stiffness should be assessed in individuals presenting altered ankle, knee and hip movement during gait. [ABSTRACT FROM AUTHOR]

Background: Naturally aligned toes, particularly hallux, have reported with gripping functions during locomotion, thus expanding the forefoot loading area.Research Question: The purpose of this study was aimed to investigate the influence of hallux abduction manipulation on the foot plantar pressure distribution and inter-segment kinematic alterations.Methods: Thirteen subjects participated in this toe manipulation study. A Footscan® pressure plate and Vicon motion capture system were utilized for the measurement of plantar pressure distribution and lower extremity and foot inter-segment kinematics during walking and running. Paired-sample t-test from statistical parametric mapping 1d was used to check the kinematic significance.Results: Peak pressure in third metatarsal (M3) increased significantly during walking under manipulation. Contact area increased in second metatarsal (M2) with manipulation during running. Peak pressure and pressure-time integral illustrated significant increases in M3, and the maximum force and impulse in fourth metatarsal (M4) increased significantly. Arch height index increased while walking with toe manipulation. The foot progression angle in the frontal plane showed significant decrease in mid-swing phase during walking and significant increase in mid-stance phase during running. The hallux relative to forefoot angles presented higher axial rotation in the frontal plane.Significance: Findings form this study showed centrally and laterally redistributed foot loadings and increased forefoot inter-segment flexibility with manipulation, which may be used as baseline to evaluate toe-manipulation interventions in foot disorders, specifically hallux valgus deformity. [ABSTRACT FROM AUTHOR]

Following incomplete spinal cord injury, people often move slowly in an effort to maintain stability during walking maneuvers. Here we examine how maneuver speed impacts frontal-plane stability in people with incomplete spinal cord injury. We hypothesized that the challenge to control frontal-plane stability would increase with maneuver speed; specifically, the minimum lateral margin of stability would be smaller and the required coefficient of friction to avoid a slip would be greater during fast vs. preferred speed maneuvers. We measured kinematics and ground reaction forces as 12 individuals with incomplete spinal cord injury performed side-step, lateral maneuvers at preferred and fast speeds. We examined four sequential steps: the Setup and Pushoff steps initiated the maneuver, and the Landing and Recovery steps arrested the maneuver. Our hypotheses were partially supported. Maneuver time was shorter during fast vs. preferred speed maneuvers (p = 0.003). Minimum lateral margin of stability was smaller during the Setup step of fast vs. preferred speed maneuvers (p = 0.026). We found no differences in minimum lateral margin of stability between speeds for the Landing and Recovery steps (p > 0.05). The required coefficient of friction was not different between fast and preferred speed maneuvers (p = 0.087). The greatest effect of increasing maneuver speed occurred during the Setup step; as speed increased, participants reduced their minimum lateral margin of stability ipsilateral to the maneuver direction. This action allowed maneuvers to be performed more quickly without requiring a greater lateral impulse during the Pushoff step. However, this strategy reduced passive stability. • People with incomplete spinal cord injury can increase walking maneuver speed. • People reduced their margin of stability as lateral maneuver speed increased. • Reducing the lateral margin of stability will enable faster maneuvers. [ABSTRACT FROM AUTHOR]

• This is the first experimental study on the thrust of flutter kick by humans. • The thrust by humans is lower than what is reported in aquatic animals. • The study reports the relationship between post-activation potentiation and kicking performance. • Post-activation potentiation increases thrust, which is going to enhance the kicking kinematics. • Kicking kinematics will thereby improve performance. Herein, we analyse by experimental techniques the human kicking thrust and measure the effect of a warm-up routine that includes post-activation potentiation (PAP) sets on front-crawl flutter kick thrust, kinematics, and performance. Sixteen male competitive swimmers with 22.13 ± 3.84 years of age were randomly assigned in a crossover manner to undergo a standard warm-up (non-PAP; control condition) and a warm-up that included PAP sets (PAP; experimental condition) consisting in 2 × 5 repetitions of unloaded countermovement jump. Participants performed a 25 m all-out trial in front-crawl with only flutter kicks eight min after each warm-up. Kinetics (i.e., peak thrust, mean thrust, and thrust-time integral) and kinematics (i.e., speed, speed fluctuation and kicking frequency) were experimentally collected by an in-house customized system composed of differential pressure sensors, speedo-meter, and underwater camera. Peak thrust (P = 0.02, d = 0.66) and mean thrust (P = 0.10, d = 0.40) were increased by 15% in PAP compared to non-PAP. Large and significant differences were noted in speed (P = 0.01, d = 0.54) and speed fluctuation (P = 0.02, d = 0.58), which improved by 10% in PAP compared with non-PAP. In conclusion, a warm-up that includes PAP sets improves kicking thrust, kinematics and performance. [ABSTRACT FROM AUTHOR]

Background: In many common multi-tasks, vision is used for two or more of the tasks, such as viewing cars, traffic signals, and the sidewalk curb at a crosswalk.Research Question: How does gaze diversion affect adaptive locomotion in young adults?Methods: Seventeen young adults completed a simple reaction time (RT) task while (1) standing and (2) during the approach to an obstacle on an 8 m walkway. Participants pressed a remote switch in response to a light cue (activated once during approach phase). The light cue was located either (1) on the obstacle (gaze diverted to obstacle) or (2) at eye level (gaze diverted away from obstacle). A gait baseline task with no RT task was included.Results: An interaction was observed (task (standing versus walking) by gaze location (on versus away from obstacle), p = 0.01), where RT was not affected by the gaze location in the standing task, but RT was longer when gaze was diverted away from the obstacle in the gait task. Furthermore, trail foot placement was closer to the obstacle when the gaze was diverted away from the obstacle (p = 0.002), which increased risk of tripping.Significance: Gaze diversion did not affect cognitive performance in the standing task, as information regarding the obstacle was not relevant for the standing task. However, completing a simple discrete visual cognitive task during obstacle crossing impaired both cognitive and gait performance, but only when gaze was diverted away from the obstacle. The impaired performance is likely due to the larger amount of structural interference when gaze was diverted away from the obstacle. These findings highlight the critical role of vision during the approach phase to an obstacle. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the present study was to investigate the effect of the unloader brace on medial compartment dynamic joint space (DJS) during gait, while simultaneously recording ground reaction force (GRF) in varus knee osteoarthritis (OA) patients using a highly accurate biplane radiography system which allowed continuous measurement of DJS from heel strike through the midstance phase of gait. The hypothesis was that DJS in the medial compartment would be greater with the unloader brace than without the brace during gait.Methods: After 2 weeks of daily use of the unloader brace, ten varus knee OA patients (age 52 ± 8 years) walked with and without the brace on an instrumented treadmill, while biplane radiographs of the OA knees were acquired at 100 Hz. Medial compartment DJS was determined from heel strike to terminal stance (0-40% of the gait cycle) using a validated volumetric model-based tracking process that matches subject-specific 3D bone models to the biplane radiographs. The GRF during gait was collected at 1000 Hz. Repeated-measures ANOVA was used to explore differences in medial compartment DJS and GRF between the unbraced and braced conditions. A patient-reported subjective questionnaire related to the brace use was collected at the time of the test.Results: Medial compartment DJS was significantly greater with the unloader brace than without the brace during gait (P = 0.005). The average difference was 0.3 mm (95% confidence interval 0.1-0.4 mm). No significant difference was observed in terms of vertical GRF between the two conditions. The questionnaire showed participants felt reduced pain when wearing the brace.Conclusion: The unloader brace has the significant effect of increasing medial compartment DJS during gait, which supports the underlying premise that the unloader brace reduces pain by increasing medial joint space during dynamic loading activities.Level Of Evidence: III. [ABSTRACT FROM AUTHOR]

The purpose of this study was to explore the extent of multifractality in unperturbed and constrained locomotion, and to determine if multifractality predicted gait adaptability. Young, healthy participants (n = 15) walked at preferred and slow speeds, as well as asymmetrically (one leg at half speed) on a split-belt treadmill. Stride time multifractality was assessed via local detrended fluctuation analysis, which evaluates the evolution of fluctuations both spatially and temporally. Unperturbed walking exhibited monofractal behavior. Asymmetric walking displayed greater multifractality in the faster moving limb, indicating more intermittent periods of extreme high or low variance. Multifractality was not associated with adaptation to asymmetric walking. These findings further suggest that unperturbed locomotion is monofractal and establish that perturbed walking yields multifractal behavior. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the effects of galvanic vestibular stimulation (GVS) on path trajectory and body rotation during a triangle completion task. Participants (N = 17, female, 18-30 years) completed the triangle completion task in virtual reality using two different size triangles. GVS was delivered at three times each participant's threshold in either the left or right direction prior to the final leg of the triangle and continued until the participant reached their final position. Whole body kinematics were collected using an NDI Optotrak motion tracking system. Results revealed a significant main effect of GVS on arrival error such that no GVS (NGVS) had significantly smaller arrival errors than when GVS was administered. There was also a significant main effect of GVS on angular error such that NGVS had significantly smaller error than GVSaway and GVStowards. There was no significant difference between GVS trials in path variability during the final leg on route to the final position. These results demonstrate that vestibular perturbation reduced the accuracy of the triangle completion task, affecting path trajectory and body position during a path integration task in the absence of visual cues. [ABSTRACT FROM AUTHOR]

Background: Locomotion on stairs is challenging for balance control and relates to a significant number of injurious falls. The visual system provides relevant information to guide stair locomotion and there is evidence that peripheral vision is potentially important.Research Question: This study investigated the role of the lower visual field information for the control of stair walking. It was hypothesized that restriction in the lower visual field (LVF) would significantly impact gaze and locomotor behaviour specifically during descent and during transition phases emphasizing the importance of the LVF information during online control.Methods: Healthy young adults (n = 12) ascended and descended a 7-step staircase while wearing customized goggles that restricted the LVF. Three visual conditions were tested: full field of view (FULL); 30° (MILD), and 15° (SEVERE) of lower field of view available. Stride time, head pitch angle and handrail use were assessed during approach, transition steps (two steps at the top and bottom of the stairs) and middle step phases.Results: Transient downward head pitch angle increased with LVF restriction, while walk speed decreased and handrail use increased. Occlusion impaired stair descent more strongly than ascent reflected by a larger downward head pitch angles and slower walk times. LVF restriction had a greater influence on stride time and head angle during the approach and first transition compared to other stair regions.Significance: Information from the lower visual field is important to guide stair walking and particularly when negotiating the first few steps of a staircase. Restriction in the lower visual field during stair walking results in more cautious locomotor behaviour such as walking slower and using the handrails. In daily activities, tasks or conditions that restrict or alter the lower visual field information may elevate the risk for missteps and falls. [ABSTRACT FROM AUTHOR]

Background: The number of individuals participating in organised races is increasing, with few studies undertaken in ecologically-valid settings. Running involves cyclical movements and activation of lower-extremity muscles, with fatigue and foot-strike pattern proposed as factors contributing to running-related injuries.Research Question: Our aim was to investigate the effects of running a 12-km race on plantar pressure distribution, postural balance, foot-strike pattern, and plantar-flexion strength. A secondary aim was to compare actual versus anticipated race finishing times and foot-strike patterns.Methods: Twenty-four recreationally competitive runners (15 males, 9 females) completed the following tests immediately before and after a 12-km race: (1) plantar pressure distribution in self-selected bilateral stance; (2) 30-seconds eyes-closed feet-together postural balance; (3) running foot-strike angle; and (4) peak plantar-flexion isometric force. In-race foot-strike angle and patterns were also assessed at 3 and 10 km.Results: Post-race left and right foot plantar pressure distribution, postural balance, and plantar-flexion force measures significantly differed from pre-race measures. These changes were associated with small to large standardised effects (absolute ES: 0.42 to 0.94). On average, the relative pressure under the left foot decreased by 3.2 ± 5.0%; the centre of pressure path length and area of the 95th percentile ellipse from the balance test increased by 5.7 ± 8.9 cm and 18.2 ± 21.3 cm2; and peak plantar-flexion isometric force decreased by 0.23 ± 0.28 times body weight. Participants predicted their finishing times relatively well, but not their foot-strike patterns. No meaningful change in foot-strike angle or pattern was observed pre- to post-race, or between 3 and 10 km.Significance: Running a 12-km race influenced neuromuscular measures, confirming racing-induced fatigue in our recreationally competitive runners. However, these alterations did not lead to observable changes in foot-strike pattern, indicating that this measure might not be appropriate for quantifying fatigue in recreationally competitive runners. [ABSTRACT FROM AUTHOR]

Background: Circumvention of pedestrians is an essential requirement of community ambulation and can be challenging to reproduce in laboratory or clinical settings. Virtual reality (VR) is a powerful tool that allows investigations, assessments or training of such tasks under ecological but controlled conditions. The extent to which current VR technologies can elicit responses similar to those observed in the physical world, however, remains to be determined.Research Questions: (1) To what extent does the circumvention of static pedestrians in VR differ from that observed in the physical environment (PE)? and; (2) To what extent does the inter-trial variability of obstacle circumvention outcomes differ in VR vs. the PE?Methods: Healthy young participants (n = 13) were assessed while walking and avoiding a collision with an interferer that stood either at 3.0 and 3.5 m from the participant's starting position (experimental trials) or that exited to the side (catch trials). The task was performed in the PE and VE, in a random order. A female collaborator acted as interferer in the PE and her kinematics was used to create the avatar used in the VE.Results: Compared to the PE, the circumvention of a static pedestrian in VR was characterized by larger obstacle clearances and slower walking speeds. Characteristics of circumvention strategy such as the preferred side of circumvention, response to obstacle position and pattern of speed adaptation were similar between VR and the PE. Inter-trial variability for the different outcomes were also similar between the two environments.Significance: Differences in obstacle clearance and speed indicate the use of "safer" circumvention strategies in VR. However, the patterns of locomotor adaptation that were largely similar between the two environments which suggests that VR is a valuable tool to study, assess and possibly train complex locomotor tasks such as obstacle avoidance. [ABSTRACT FROM AUTHOR]