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Background Falls among community-dwelling older adults are often triggered by uneven walkways. Joint coordination and its variability change with age and may place older adults at risk of falling. It is unclear how irregular surfaces impact lower-limb joint coordination and if such changes are exacerbated by aging. Research question To what extent do lower-limb inter-joint coordination and its variability, over flat and uneven brick walkways, differ between older and young healthy adults? Methods A motion-capture system collected kinematic data from walking trials on flat and uneven walkways in seventeen older (72.0 ± 4.2 years) and eighteen younger (27.0 ± 4.7 years) healthy adults. Continuous relative phase analyses were performed for the Knee-Hip and Ankle-Knee joint pairs. Mean Absolute Relative Phase (MARP) quantified coordination amplitude. Deviation Phase (DP) quantified coordinative variability. Two-way mixed ANOVA’s tested for effects of age, surface, and age × surface interactions. Results Uneven surfaces prompted more in-phase MARP inter-joint coordination in adults during most gait phases (p ≤ 0.024). Age × surface interactions were observed during initial contact (Ankle-Knee: p = 0.021, Knee-Hip: p = 0.001) and loading response (Knee-Hip: p = 0.017), with post-hoc analyses showing coordination accentuated in older adults. Uneven surfaces induced higher DP in Knee-Hip (p = 0.017) and Ankle-Knee joint coupling (p

Observations from laboratory-based gait analysis are difficult to extrapolate to real-world environments where gait behavior is modulated in response to complex environmental conditions and surface profiles. Inertial measurement units (IMUs) permit real-world gait analysis; however, automatic detection of surfaces encountered remains largely unexplored. The aims of this study are to quantify for machine learning models the effect of (1) random and subject-wise data splitting and (2) sensor location and count on surface classification performance. Thirty participants walked on nine surface conditions (flat-even, slope-up, slope-down, stairs-up, stairs-down, cobblestone, grass, banked-left, banked-right) wearing IMUs (wrist, trunk, bilateral thighs, bilateral shanks). Data were separated into gait cycles, normalized to 101 samples, and spilt into train and test sets (85 and 15%, respectively). For random splitting, trials were randomly assigned to the train or test set. In subject-wise splitting, all trials from 4 random participants were selected for testing. Linear discriminant analysis extracted features from the IMUs. Features were delivered to a neural network. F1-score evaluated model performance. Models achieved F1 scores of 0.96 and 0.78 using random and subject-wise splitting, respectively. Random splitting performance was mainly invariant to sensor location/count; however, subject-wise splitting showed best performance using lower-limb sensors. In general, stairs and sloped surfaces were easily predicted (F1 0.85) while banked surfaces were challenging, especially for subject-wise models (F1 ≈ 0.6). Neural networks can detect surfaces based on subtle changes in walking behavior captured by IMUs. Data splitting approaches and sensor location/count (subject-wise) have a non-negligible effect on model performance.

Background Inter-joint coordination and variability during gait provide insight into control and adaptability of the neuromuscular system. To date, coordination research has been restricted to laboratory settings, and it is unclear how these findings translate to real-world, outdoor walking environments. Research Question Compared to flat walking, to what extent do outdoor surfaces impact lower-limb inter-joint coordination and variability during gait, in healthy adults? Methods Data from inertial measurement units placed on the lower-back, thigh, and shank were extracted from thirty healthy young adults (15 females, 23.5 ± 4.2 years) during outdoor walking on flat (paved sidewalk); irregular (cobblestone, grass); sloped (slope-up, slope-down); and banked (banked-right, banked-left) surfaces. Sagittal joint angles for the right knee and hip were computed and partitioned by gait phase (stance and swing). Continuous Relative Phase analysis determined inter-joint coordination and variability for the knee-hip joint pair using Mean Absolute Relative Phase (MARP) and Deviation Phase (DP), respectively. One-way repeated measures ANOVAs tested surface effects. Post-hoc Bonferroni adjusted surface comparisons were assessed. Results Significant knee-hip surface effects were seen during all gait phases for MARP (p

Background Clinical tests of foot posture and mobility are not strongly related to the dynamic kinematics of the foot during gait. These measures may be more directly related to foot and ankle kinetics. The supination resistance test (SRT) is a clinical test that may more directly measure forces acting on the weightbearing foot to provide clinicians with insight about the loading of foot structures. Research Question What is the relationship between the SRT in relaxed calcaneal stance and in single-leg-stance and the kinetics and kinematics of the foot and ankle during gait? Methods 10 healthy adults between the ages of 18 and 65 were recruited to participate in this study. Three-dimensional motion analysis was performed using the Oxford Foot Model during gait. The results of the SRT were compared with peak midfoot and ankle joint moments, power generation and absorption, joint angles, and peak angular velocities and accelerations. Correlation coefficients were calculated to assess the strength of relationships between these variables and the SRT. Results The SRT demonstrated significant relationships with several variables. In relaxed calcaneal stance, the SRT was inversely related to maximum midfoot pronation moments (r = −0.51), maximum midfoot plantarflexion moments (rho = −0.71), and peak midfoot power generation (r = −0.61). In single-leg-stance, the SRT was significantly related to maximum midfoot plantarflexion moments (rho = −0.55) and peak midfoot power generation (r = −0.47). Significance The SRT is significantly associated to several kinetic variables that quantify midfoot loading during gait. Interventions that decrease supination resistance may have the potential to increase midfoot power generation.

This study examined the effects of four micro-travel keyboards on forearm muscle activity, typing force, typing performance, and self-reported discomfort and difficulty. Twenty participants completed typing tasks on four commercially available devices with different key switch characteristics (dome, scissors, and butterfly) and key travels (0.55, 1.3, and 1.6 mm). The device with short travel (0.55 mm) and a dome type key switch mechanism was associated with higher muscle activities (6–8%,p < 0.01), higher typing force (12%, p < 0.001), slower typing speeds (8%, p < 0.01), and twice as much discomfort (p < 0.05), compared to the three other devices: short travel (0.55 mm) and butterfly switch design and long travel (1.3 and 1.6 mm) with scissor key switches. Participants rated the devices with larger travels (1.3 and 1.6 mm) with least discomfort (p = 0.015) and difficulty (p < 0.001). When stratified by sex/gender, these observed associations were larger and more significant in the female participants compared to male participants. Because the devices with similar travel but different key switch designs had difference in outcomes and devices with different travel were not different, and the results suggest that key travel alone does not predict typing force or muscle activity.

Changing directions while walking (turning gait), often with little planning time, is essential to navigating irregular surfaces in the built-environment. It is unclear how older adults reorient their bodies under these constraints and whether adaptations are related to declines in physiological characteristics.The aims of this study were to (1) investigate whether surface irregularity, late-cueing, and age negatively affect coordination, kinematics, and center of mass (COM) movement during 90° turning gait and (2) determine if adaptations correlate with declines in strength, balance, and reaction-time.Eighteen young (18-35 years) and sixteen older (65+ years) healthy adults participated in the study. Retro-reflective marker and trunk-accelerometry data were used to compute upper-body segmental reorientation timing, upper-body kinematics, and COM movement characteristics. Balance scores, lower-limb strength, and choice-reaction-times were also recorded.Young and older adults maintained a cranial-caudal (head, shoulders, pelvis) reorientation sequence (p ≤ 0.018), lowered head pitch (uneven surface; young p = 0.035 and old p 0.001), increased maximum COM acceleration (uneven surface and late-cueing; p ≤ 0.002), and decreased COM smoothness (uneven surface; p 0.001). Young adults increased shoulder roll (uneven surface and late-cueing; p ≤ 0.008). Reduced stride regularity (late-cueing) was observed in older (p 0.001), compared to young (p = 0.017), adults. Declines in strength (p ≤ 0.040) and balance (p = 0.018) were correlated with gait adaptations of older adults.Late-cueing on an uneven surface is challenging for older adults. These challenges are exacerbated by strength and balance deficits.

The aim of this study was to investigate if a machine learning algorithm utilizing triaxial accelerometer, gyroscope, and magnetometer data from an inertial motion unit (IMU) could detect surface- and age-related differences in walking. Seventeen older (71.5 ± 4.2 years) and eighteen young (27.0 ± 4.7 years) healthy adults walked over flat and uneven brick surfaces wearing an inertial measurement unit (IMU) over the L5 vertebra. IMU data were binned into smaller data segments using 4-s sliding windows with 1-s step lengths. Ninety percent of the data were used as training inputs and the remaining ten percent were saved for testing. A deep learning network with long short-term memory units was used for training (fully supervised), prediction, and implementation. Four models were trained using the following inputs: all nine channels from every sensor in the IMU (fully trained model), accelerometer signals alone, gyroscope signals alone, and magnetometer signals alone. The fully trained models for surface and age outperformed all other models (area under the receiver operator curve, AUC = 0.97 and 0.96, respectively; p ≤ .045). The fully trained models for surface and age had high accuracy (96.3, 94.7%), precision (96.4, 95.2%), recall (96.3, 94.7%), and f1-score (96.3, 94.6%). These results demonstrate that processing the signals of a single IMU device with machine-learning algorithms enables the detection of surface conditions and age-group status from an individual’s walking behavior which, with further learning, may be utilized to facilitate identifying and intervening on fall risk.

The purpose of this study was to investigate weight-bearing knee joint kinematic and neuromuscular responses during lateral, posterior, rotational, and combination (simultaneous lateral, posterior, and rotational motions) perturbations and post-perturbations phases in 30° flexed-knee and straight-knee conditions. Thirteen healthy female athletes participated. Knee joint angles and muscle activity of vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), semitendinosus (ST), lateral gastrocnemius (LG), and medial gastrocnemius (MD) muscles were computed. Knee abducted during lateral perturbations, whereas it adducted during the other perturbations. It was internally rotated during flexed-knee and externally rotated during straight-knee perturbations and post-perturbations. VL and VM's mean and maximum activities during flexed-knee perturbations were greater than those of straight-knee condition. BF's mean activities were greater during flexed-knee perturbations compared with straight-knee condition, while its maximum activities observed during combination perturbations. ST's maximum activities during combination perturbations were greatest compared with the other perturbations. LG and MG's activities were greater during straight-knee conditions. Compared with the perturbation phase, the mean and maximum muscles' activities were significantly greater during post-perturbations. The time of onset of maximum muscle activity showed a distinctive pattern among the perturbations and phases. The perturbation direction is an important variable which induces individualized knee kinematic and neuromuscular response.

Background Running is a popular physical activity that benefits health; however, running surface characteristics may influence loading impact and injury risk. Machine learning algorithms could automatically identify running surface from wearable motion sensors to quantify running exposures, and perhaps loading and injury risk for a runner. Research question (1) How accurately can machine learning algorithms identify surface type from three-dimensional accelerometer sensors? (2) Does the sensor count (single or two-sensor setup) affect model accuracy? Methods Twenty-nine healthy adults (23.3 ± 3.6 years, 1.8 ± 0.1 m, and 63.6 ± 8.5 kg) participated in this study. Participants ran on three different surfaces (concrete, synthetic, woodchip) while fit with two three-dimensional accelerometers (lower-back and right tibia). Summary features (n = 208) were extracted from the accelerometer signals. Feature-based Gradient Boosting (GB) and signal-based deep learning Convolutional Neural Network (CNN) models were developed. Models were trained on 90% of the data and tested on the remaining 10%. The process was repeated five times, with data randomly shuffled between train-test splits, to quantify model performance variability. Results All models and configurations achieved greater than 90% average accuracy. The highest performing models were the two-sensor GB and tibia-sensor CNN (average accuracy of 97.0 ± 0.7 and 96.1 ± 2.6%, respectively). Significance Machine learning algorithms trained on running data from a single- or dual-sensor accelerometer setup can accurately distinguish between surfaces types. Automatic identification of surfaces encountered during running activities could help runners and coaches better monitor training load, improve performance, and reduce injury rates.

Background Muscle co-contraction is an accepted clinical measure to quantify the effects of aging on neuromuscular control and movement efficiency. However, evidence of increased muscle co-contraction in old compared to young adults remains inconclusive. Research Question Are there differences in lower-limb agonist/antagonist muscle co-contractions in young and old adults, and males and females, during walking and stair use? Methods In a retrospective study, we analyzed data from 20 healthy young and 19 healthy old adults during walking, stair ascent, and stair descent at self-selected speeds, including marker trajectories, ground reaction force, and electromyography activity. We calculated muscle co-contraction at the knee (vastus lateralis vs. biceps femoris) and ankle (tibialis anterior vs. medial gastrocnemius) using the ratio of the common area under a muscle pairs’ filtered and normalized electromyography curves to the sum of the areas under each muscle in that pair. Results Old compared to young adults displayed 18%–22% greater knee muscle co-contractions during the entire cycle of stair use activities. We found greater (17%–29%) knee muscle co-contractions in old compared to young adults during the swing phase of walking and stair use. We found no difference in ankle muscle co-contractions between the two age groups during all three activities. We found no difference in muscle co-contraction between males and females at the knee and ankle joints for all three activities. Significance Based on our findings, we recommend clinical evaluation to quantify the effects of aging through muscle co-contraction to include the knee joint during dynamic activities like walking and stair use, and independent evaluation of the stance and swing phases.

The forward skating start is a fundamental skill for ice hockey players, yet extremely challenging given the low traction of the ice surface. The technique for maximum skating acceleration of the body is not well understood. The aim of this study was to evaluate kinematic ice hockey skating start movement technique in relation to a skater’s skill level. A 10-camera motion capture system placed on the ice surface recorded “hybrid-V” skate start movement patterns of high and low calibre male ice hockey players (n = 7, 8, respectively). Participants’ lower body kinematics and estimated body centre of mass (CoM) movement during the first four steps were calculated. Both skate groups had similar lower body strength profiles, yet high calibre skaters achieved greater velocity; skating technique differences most likely explained the performance differences between the groups. Unlike over ground sprint start technique, skating starts showed greater concurrent hip abduction, external rotation and extension, presumably for ideal blade-to-ice push-off orientation for propulsion. Initial analysis revealed similar hip, knee and ankle joint gross movement patterns across skaters, however, further scrutiny of the data revealed that high calibre skaters achieved greater vertical CoM acceleration during each step that in turn allowed greater horizontal traction, forward propulsion, lower double-support times and, accordingly, faster starts with higher stride rates.

Turning while walking is a crucial component of locomotion, often performed on irregular surfaces with little planning time. Turns can be difficult for some older adults due to physiological age-related changes. Two different turning strategies have been identified in the literature. During step turns, which are biomechanically stable, the body rotates about the outside limb, while for spin turns, generally performed with closer foot-to-foot distance, the inside limb is the main pivot point. Turning strategy preferences of older adults under challenging conditions remains unclear. The aim of this study was to determine how turning strategy preference in healthy older adults is modulated by surface features, cueing time, physiological characteristics of aging, and gait parameters. Seventeen healthy older adults (71.5 ± 4.2 years) performed 90° turns for two surfaces (flat, uneven) and two cue conditions (pre-planned, late-cue). Gait parameters were identified from kinematic data. Measures of lower-limb strength, balance, and reaction-time were also recorded. Generalized linear (logistic) regression mixed-effects models examined the effect of (1) surface and cuing, (2) physiological characteristics of ageing, and (3) gait parameters on turn strategy preference. Step turns were preferred when the condition was pre-planned (p

Background Patients with knee osteoarthritis often present with varus thrust and muscular co-contraction during gait. It is unclear if these adaptations are related. The objective was to examine the relationship between muscle co-contraction and varus thrust during gait in patients with knee osteoarthritis and to determine if these relationships are modulated by disease severity or history of knee ligament rupture. Methods Participants (n = 42, 23 women, mean age 58 years) with knee osteoarthritis completed gait trials at self-selected speeds. Varus thrust was measured with an eight camera motion capture system sampled at 100 Hz. Co-contraction ratios were measured with surface electromyography sampled at 2000 Hz over the quadriceps, hamstrings, and gastrocnemius. Disease severity was measured on radiographs and history of anterior cruciate ligament rupture was confirmed on magnetic resonance imaging. Linear regression analyses examined the relationship between varus thrust and co-contraction ratios after controlling for radiographic disease severity and history of anterior cruciate ligament rupture. Findings Higher vastus lateralis–lateral hamstring (b = 0.081, P 0.05). Radiographic disease severity or history of anterior cruciate ligament injury did not significantly contribute to regression models. Interpretation Greater quadriceps-hamstring co-contraction is associated with greater varus thrust in patients with knee osteoarthritis. Potential explanations include increased co-contraction may provide stability or there is a proprioceptive reflex that is independent of any stabilizing role. Research is needed to test these hypotheses.

Background Turning while walking is a crucial component of locomotion that is performed using an outside (step) or inside (spin) limb strategy. The aims of this paper were to determine how children with cerebral palsy perform turning maneuvers and if specific kinematic and kinetic adaptations occur compared to their typically developing peers. Methods Motion capture data from twenty-two children with cerebral palsy and fifty-four typically developing children were collected during straight and 90° turning gait trials. Experimental data were used to compute spatio-temporal parameters, margin of stability, ground reaction force impulse, as well as joint kinematics and kinetics. Findings Both child groups preferred turning using the spin strategy. The group of children with cerebral palsy exhibited the following adaptations during turning gait compared to the typically developing group: stride length was decreased across all phases of the turn with largest effect size for the depart phase (2.02), stride width was reduced during the turn phase, but with a smaller effect size (0.71), and the average margin of stability during the approach phase of turning was reduced (effect size of 0.98). Few overall group differences were found for joint kinematic and kinetic measures; however, in many cases, the intra-subject differences between straight walking and turning gait were larger for the majority of children with cerebral palsy than for the typically developing children. Interpretation In children with cerebral palsy, turning gait may be a better discriminant of pathology than straight walking and could be used to improve the management of gait abnormalities.

Flat feet in children are common, and at times symptomatic, but the relationship between function and symptoms or impairment is still unclear. We undertook a prospective, observational study comparing children with paediatric flexible flat foot (PFF) and children with neutral feet (NF) using three dimensional gait analysis (3DGA). It was hypothesised that children with PFF would demonstrate differences in both spatio-temporal parameters of gait and foot and ankle kinematics compared to the NF group and that these differences would correlate with impaired quality of life (QoL). The kinematic differences were expected to be most marked in hindfoot coronal plane motion and forefoot sagittal and transverse plane motion. Eighty-three children between the ages of 8 and 15 were recruited in this study: Forty-two were classified as having PFF and forty-one as NF. Each child underwent 3DGA and completed the Oxford Ankle Foot Questionnaire for Children (OxAFQ_C). Reduced OxAFQ_C physical domain scores in the PFF children were associated with slower walking speed (p=0.014) and reduced normalised stride length (p=0.008). PFF children also demonstrated significantly increased hindfoot eversion and forefoot supination during gait. Significant differences between groups were not observed for other foot and ankle joint motions. Increased maximum hindfoot eversion and increased forefoot supination correlated strongly with lower QoL scores in PFF children. These data further our understanding of the functional characteristics that lead to impaired QoL in PFF children. These findings will help guide the surveillance and management of children with this ubiquitous condition.

Background Outdoor falls in community-dwelling older adults are often triggered by uneven pedestrian walkways. It remains unclear how older adults adapt to uneven surfaces typically encountered in the outdoor built-environment and whether these adaptations are associated to age-related physiological changes. Research question The aims of this study were to (1) compare gait parameters over uneven and flat brick walkways, (2) evaluate the differences between older and young adults for these two surfaces, and (3) assess if physiological characteristics could predict adaptations in older adults. Methods Balance, strength, reaction-time, full-body marker positions, and acceleration signals from a trunk-mounted inertial measurement unit were collected in seventeen older (71.5 ± 4.2 years) and eighteen young (27.0 ± 4.7 years) healthy adults to compute lower-limb joint kinematics, spatio-temporal parameters, dynamic stability, and accelerometry-derived metrics (symmetry, consistency, and smoothness). Results Both groups increased hip flexion at foot-strike, while decreasing ankle dorsiflexion, margin of stability, symmetry, and consistency on the uneven, compared to flat, surface. Older, compared to young, adults showed a larger increase in knee flexion at foot-strike and a larger decrease in smoothness on the uneven surface. Only young adults decreased hip abduction on the uneven surface. Strength, not balance nor reaction-time, was the main predictor of hip abduction in older adults on both surfaces. Significance While older adults may be especially vulnerable, uneven surfaces negatively impact gait, irrespective of age, and could represent a risk to all pedestrians.

The forward skating start is a fundamental skill for male and female ice hockey players. However, performance differences by athlete's sex cannot be fully explained by physiological variables; hence, other factors such as skating technique warrant examination. Therefore, the purpose of this study was to evaluate the body movement kinematics of ice hockey skating starts between elite male and female ice hockey participants. Male (n = 9) and female (n = 10) elite ice hockey players performed five forward skating start accelerations. An 18-camera motion capture system placed on the arena ice surface captured full-body kinematics during the first seven skating start steps within 15 meters. Males' maximum skating speeds were greater than females. Skating technique sex differences were noted: in particular, females presented ~10° lower hip abduction throughout skating stance as well as ~10° greater knee extension at initial ice stance contact, conspicuously followed by a brief cessation in knee extension at the moment of ice contact, not evident in male skaters. Further study is warranted to explain why these skating technique differences exist in relation to factors such as differences in training, equipment, performance level, and anthropometrics.

Stairs represent a barrier to safe locomotion for some older adults, potentially leading to the adoption of a cautious gait strategy that may lack fluidity. This strategy may be characterized as unsmooth; however, stair negotiation smoothness has yet to be quantified. The aims of this study were to assess age- and task-related differences in head and body center of mass (COM) acceleration patterns and smoothness during stair negotiation and to determine if smoothness was associated with the timed "Up and Go" (TUG) test of functional movement. Motion data from nineteen older and twenty young adults performing stair ascent, stair descent, and overground straight walking trials were analyzed and used to compute smoothness based on the log-normalized dimensionless jerk (LDJ) and the velocity spectral arc length (SPARC) metrics. The associations between TUG and smoothness measures were evaluated using Pearson's correlation coefficient (r). Stair tasks increased head and body COM acceleration pattern differences across groups, compared to walking (p 0.05). LDJ smoothness for the head and body COM decreased in older adults during stair descent, compared to young adults (p ≤ 0.015) and worsened with increasing TUG for all tasks (-0.60 ≤ r ≤ -0.43). SPARC smoothness of the head and body COM increased in older adults, regardless of task (p 0.001), while correlations showed improved SPARC smoothness with increasing TUG for some tasks (0.33 ≤ r ≤ 0.40). The LDJ outperforms SPARC in identifying age-related stair negotiation adaptations and is associated with performance on a clinical test of gait.

Turning is a common locomotor task essential to daily activity; however, very little is known about the forces and moments responsible for the kinematic adaptations occurring relative to straight-line gait in typically developing children. Thus, the aims of this study were to analyse ground reaction forces (GRFs), ground reaction free vertical torque (TZ), and the lower-limb joint kinetics of 90° outside (step) and inside (spin) limb turns. Step, spin, and straight walking trials from fifty-four typically developing children were analysed. All children were fit with the Plug-in Gait and Oxford Foot Model marker sets while walking over force plates embedded in the walkway. Net internal joint moments and power were computed via a standard inverse dynamics approach. All dependent variables were statistically analysed over the entire curves using the mean difference 95% bootstrap confidence band approach. GRFs were directed medially for step turns and laterally for spin turns during the turning phase. Directions were reversed and magnitudes decreased during the approach phase. Step turns showed reduced ankle power generation, while spin turns showed large TZ. Both strategies required large knee and hip coronal and transverse plane moments during swing. These kinetic differences highlight adaptations required to maintain stability and reorient the body towards the new walking direction during turning. From a clinical perspective, turning gait may better reveal weaknesses and motor control deficits than straight walking in pathological populations, such as children with cerebral palsy, and could potentially be implemented in standard gait analysis sessions.

Spatio-temporal parameters (STPs) are fundamental gait measures often used to compare children of different ages or gait ability. In the first case, non-dimensional normalisation (ND) of STPs using either leg-length or height is frequently conducted even though the process may not remove known inter-subject variability. STPs of children with and without disability can be compared through matched databases or using regression driven prediction. Unfortunately, database assignment is largely arbitrary and previous regressions have employed too few parameters to be successful. Therefore, the aims of this study were to test how well actual and ND STPs could be predicted from anthropometrics and speed and to assess if self-selected speed could be predicted from anthropometrics using multivariate regression in a cohort of eighty-nine typically developing children. Equations were validated on an extraneous dataset. We found that equations for actual step length, stride length, and cadence explained more than 84% of the variance compared to their ND counterparts. Moreover, only leg-length ND versions of these parameters were linearly proportional to speed. Prediction of single and double limb support times was weaker (R(2)=0.69 and 0.72, respectively) and we were unable to predict self-selected speed (R(2)

The role of flexible flat feet (FF) in the development of musculoskeletal symptoms at joints proximal to the ankle is unclear. We undertook an observational study to investigate the relationship between foot posture and the proximal joints in children. It was hypothesised that reduced arch height would be associated with proximal joint symptoms and altered gait kinematics and kinetics particularly in the transverse plane at the hip and knee. Ninety-five children between the ages of 8-15 were recruited into this ethically approved study. Foot posture was classified using the arch height index (AHI). The frequency of knee and hip/back pain was documented, and each child underwent three dimensional gait analysis. Reduced arch height was associated with increased odds of knee symptoms (p < 0.01) and hip/back symptoms (p = 0.01). A flat foot posture was also significantly associated with a reduction in the second peak of the vertical ground reaction force (p = 0.03), which concomitantly affected late stance hip and knee moments. A reduced AHI was also associated with increased pelvic retraction and increased knee valgus in midstance. No kinematic and kinetic parameter associated with a flat foot posture related to increased proximal joint symptoms in the FF group. Children with a flatter foot posture are more likely to have pain or discomfort at the knee, hip and back; however, the mechanisms by which this occurs remain unclear. Treating FF without explicit understanding of how it relates to symptoms is difficult, and further work in this area is required.

Dynamic forces and range of motion (ROM) were measured during on-ice skating using a standard hockey skate and a modified skate (MS) with an altered tendon guard and eyelet configuration. The objective of this study was to determine if these modifications resulted in biomechanical and performance changes during on-ice skating skills. The right skate of each type was instrumented with a calibrated strain gauge force transducer system to measure medial–lateral and vertical forces during ice skating. In addition, a goniometer was placed about the ankle and rear foot to measure ROM during skating. Ten subjects executed three skills: forward skating, crossovers inside foot and crossovers outside foot. The MS demonstrated significant gains of 5°–9° in dorsi-plantarflexion ROM (p 0.05) in mean work and power output was noted with the MS, although no improved times were observed during the skating skills. Potentially, some players may need a period of familiarization to take advantage of the design alterations of the MS.

Cross-slopes are a common terrain characteristic, however there is no biomechanical knowledge of the intra-foot adaptations required for running on these surface inclinations. The purpose of this study was to evaluate the kinematic changes induced within the foot while running on a transversely inclined surface. A three-segment foot model distinguishing between the hindfoot, forefoot, and hallux was used for this purpose. Nine healthy experienced male runners volunteered to perform level (0°) and cross-slope (10°) running trials barefoot at a moderate speed. Multivariate analysis of variance (MANOVA) for repeated measures was used to analyze the kinematics of the hindfoot with respect to tibia (HF/TB), forefoot with respect to hindfoot (FF/HF), and hallux with respect to forefoot (HX/FF) during level running (LR), incline running up-slope (IRU), and incline running down-slope (IRD) conditions. In the sagittal plane, the FF/HF angle showed greater dorsiflexion at peak vertical force production (MaxFz) in IRD compared to LR (p=0.042). The HX/FF was significantly more extended during IRU than LR at foot strike (p=0.027). More importantly, frontal plane asymmetries were also found. HF/TB angles revealed greater inversion at foot strike followed by greater eversion at MaxFz for IRU compared to IRD (p=0.042 and p=0.018, respectively). For the FF/HF angle, maximum eversion was greater during IRD than LR (p=0.035). Data suggests that running on cross-slopes can induce substantial intra-foot kinematic adaptations, whether this represents a risk of injury to both recreational and professional runners remains to be determined.

Despite cross-slope surfaces being a regular feature of our environment, little is known about segmental adaptations required to maintain both balance and forward locomotion. The purpose of this study was to determine kinematic adaptations of the foot segments in relation to transverse (cross-sloped) walking surfaces. Ten young adult males walked barefoot along an inclinable walkway (level, 0° and cross-slope, 10°). Kinematic adaptations of hindfoot with respect to tibia (HF/TB), forefoot with respect to hindfoot (FF/HF), and hallux with respect to forefoot (HX/FF) in level walking (LW), inclined walking up-slope (IWU), i.e., the foot at the higher elevation, and inclined walking down-slope (IWD), i.e., the foot at the lower elevation, were measured. Multivariate analysis of variance (MANOVA) for repeated measures was used to analyze the data. In the sagittal plane, the relative FF/HF and HX/FF plantar/dorsiflexion angles differed across conditions (p=0.024 and p=0.026, respectively). More importantly, numerous frontal plane alterations occurred. For the HF/TB angle, inversion of IWU and eversion of IWD was seen at heel-strike (p

The purpose of this study was to determine the effect of cross-slope on gait dynamics. Ten young adult males walked barefoot along an inclinable walkway. Ground reaction forces (GRFs), lower-limb joint kinematics, global pelvis orientation, functional leg-length, and joint reaction moments (JRMs) were measured. Statistical analyses revealed differences across limbs (up-slope [US] and down-slope [DS]) and inclinations (level; 0°; and cross-sloped, 6°). Adaptations included increases of nearly 300% in mediolateral GRFs (p < .001), functional shortening the US-limb and elongation of the DS-limb (p < .001), reduced step width (p = .024), asymmetrical changes in sagittal kinematics and JRM, and numerous pronounced coronal plane differences including increased US-hip adduction (and adductor moment) and decreased DS-hip adduction (and adductor moment). Data suggests that modest cross-slopes can induce substantial asymmetrical changes in gait dynamics and may represent a physical obstacle to populations with restricted mobility.

Turning while walking requires substantial joint kinematic and kinetic adaptations compared to straight walking in order to redirect the body centre of mass (COM) towards the new walking direction. The role of muscles and external forces in controlling and redirecting the COM during turning remains unclear. The aim of this study was to compare the contributors to COM medio-lateral acceleration during 90 degree pre-planned turns about the inside limb (spin) and straight walking in typically developing children. Simulations of straight walking and turning gait based on experimental motion data were implemented in OpenSim. The contributors to COM global medio-lateral acceleration during the approach (outside limb) and turn (inside limb) stance phase were quantified via an induced acceleration analysis. Changes in medio-lateral COM acceleration occurred during both turning phases, compared to straight walking (p < 0.001). During the approach, outside limb plantarflexors (soleus and medial gastrocnemius) contribution to lateral (away from the turn side) COM acceleration was reduced (p < 0.001), whereas during the turn, inside limb plantarflexors (soleus and gastrocnemii) contribution to lateral acceleration (towards the turn side) increased (p ≤ 0.013) and abductor (gluteus medius and minimus) contribution medially decreased (p < 0.001), compared to straight walking, together helping accelerate the COM towards the new walking direction. Knowledge of the changes in muscle contributions required to modulate the COM position during turning improves our understanding of the control mechanisms of gait and may be used clinically to guide the management of gait disorders in populations with restricted gait ability.

The conventional gait model (CGM) is a widely used biomechanical model which has been validated over many years. The CGM relies on retro-reflective markers placed along anatomical landmarks, a static calibration pose, and subject measurements as inputs for joint angle calculations. While past literature has shown the possible errors caused by improper marker placement, studies on the effects of inaccurate subject measurements are lacking. Moreover, as many laboratories rely on the commercial version of the CGM, released as the Plug-in Gait (Vicon Motion Systems Ltd, Oxford, UK), integrating improvements into the CGM code is not easily accomplished. This paper introduces a Python implementation for the CGM, referred to as pyCGM, which is an open-source, easily modifiable, cross platform, and high performance computational implementation. The aims of pyCGM are to (1) reproduce joint kinematic outputs from the Vicon CGM and (2) be implemented in a parallel approach to allow integration on a high performance computer. The aims of this paper are to (1) demonstrate that pyCGM can systematically and efficiently examine the effect of subject measurements on joint angles and (2) be updated to include new calculation methods suggested in the literature. The results show that the calculated joint angles from pyCGM agree with Vicon CGM outputs, with a maximum lower body joint angle difference of less than 10-5 degrees. Through the hierarchical system, the ankle joint is the most vulnerable to subject measurement error. Leg length has the greatest effect on all joints as a percentage of measurement error. When compared to the errors previously found through inter-laboratory measurements, the impact of subject measurements is minimal, and researchers should rather focus on marker placement. Finally, we showed that code modifications can be performed to include improved hip, knee, and ankle joint centre estimations suggested in the existing literature. The pyCGM code is provided in open source format and available at https://github.com/cadop/pyCGM.

Background: Increased navicular drop (NDro) and navicular drift (NDri) are associated with musculoskeletal pathology in adults. The aim of this study was to investigate navicular motion in children, with respect to foot posture, and identify altered patterns of motion that demonstrate midfoot dysfunction. Navicular motion in different activities was evaluated as well as the role of flexibility and body mass index (BMI). Methods: Twenty-five children with flatfeet and 26 with neutral feet (age range, 8-15) underwent gait analysis using a 12-camera Vicon MX system (Vicon, UK). Navicular motion indices were calculated from marker coordinates. Student t tests and Pearson’s correlation coefficient (R) were used to investigate navicular motion differences between groups. The relationship between NDRo, NDRi, and their dynamic counterparts was also assessed. Results: Normalized NDri (NNDri) and normalized NDro (NNDro) correlated strongly in neutral feet (R = 0.56, P = .003) but not in flatfeet (R = 0.18, P > .05). Flatfeet demonstrated reduced NNDri compared to neutral footed children (0.7 vs 1.6, P = .007). No difference was observed in NNDro between groups. Standard and dynamic measures of NDri and NDRo were highly correlated. Navicular motion correlated poorly with BMI and flexibility. Conclusion: Motion of the navicular in the transverse and the sagittal plane is important when investigating foot function. Uncoupling of this motion in flatfeet may indicate impaired midfoot function. Reduced navicular medial translation in flatfeet may indicate altered alignment of the talonavicular joint. Clinical Relevance: The measurement of dynamic navicular motion indices did not add information about dynamic foot function compared to measurement of static indices.

Turning is a requirement for most locomotor tasks; however, knowledge of the biomechanical requirements of successful turning is limited. Therefore, the aims of this study were to investigate the spatio-temporal and lower-limb kinematics of 90° turning. Seventeen typically developing children, fitted with full body and multi-segment foot marker sets, having performed both step (outside leg) and spin (inside leg) turning strategies at self-selected velocity, were included in the study. Three turning phases were identified: approach, turn, and depart. Stride velocity and stride length were reduced for both turning strategies for all turning phases (p

Multi-segment foot models are increasingly being used to evaluate intra and inter-segment foot kinematics such as the motion between the hindfoot/tibia (ankle) and the forefoot/hindfoot (midfoot) during walking. However, kinetic analysis have been mainly restricted to one-segment foot models and could be improved by considering a multi-segment approach. Therefore, the aims of this study were to (1) implement a kinetic analysis of the ankle and theoretical midfoot joints using the existing Oxford Foot Model (OFM) through a standard inverse dynamics approach using only marker, force plate and anthropometric data and (2) to compare OFM ankle joint kinetics to those output by the one-segment foot plugin-gait model (PIG). 10 healthy adolescents fitted with both the OFM and PIG markers performed barefoot comfortable speed walking trials over an instrumented walkway. The maximum ankle power generation was significantly reduced by approximately 40% through OFM calculations compared to PIG estimates (p

Though transversely inclined (cross-sloped) surfaces are prevalent, our understanding of the biomechanical adaptations required for cross-slope locomotion is limited. The purpose of this study was to examine ground reaction forces (GRF) in cross-sloped and level walking and running. Nine young adult males walked and ran barefoot along an inclinable walkway in both level (0°) and cross-slope (10°) configurations. The magnitude and time of occurrence of selected features of the GRF were extracted from the force plate data. GRF data were collected in level walking and running (LW and LR), inclined walking and running up-slope (IWU and IRU), and down-slope (IWD and IRD), respectively. The GRF data were then analyzed using repeated measures MANOVA. In the anteroposterior direction, the timing of the peak force values differed across conditions during walking (p=.041), while the magnitude of forces were modified across conditions for running (p=.047). Most significant differences were observed in the mediolateral direction, where generally force values were up to 390% and 530% (p

The biomechanics of level running are well researched (Novacheck 1998). However, less is known about the kinematic adaptations during cross-slope running (Fujii et al. 1999, Sussman et al. 2001). C...

Introduction: Turning while walking is a crucial part of locomotion, however little is known about the biomechanics of turning maneuvers. The aim of this study was to identify the adaptations required for healthy children to navigate turns. Patients/materials and methods: Thirty-one healthy children performed barefoot walking in a straight line and 90◦ turns at self-selected veolcity. Seventeen children (12 girls, 12.6±2.3 years, height 1.6±0.1m, and leg length 0.8±0.1 m) independently chose to perform turning with both the inside (spin) and outside (step) foot, andwere retained for statistical analysis. Three turning phases were analyzed (approach, turn, and depart strides) while left and right trialswere pooled. Retroreflectivemarkerswere used to automatically detect foot strike and foot off events [1] required to compute spatio-temporal data [2]. Spatial data were normalized to leg length while absolute temporal variables were reported [3]. One-way repeated measures ANOVA with Bonferroni correction were performed on stride velocity, stance time, stride length, and stride width. Results: Half of all children turned utilizing only the spin strategy while no child solely attempted step turns. Statistical analysis revealed that both turning conditions were different from straight walking. Themain differences occurred between turning phases for step and spin conditions while only a few differences were found between turning types (Table 1). Mean [95% confidence interval]. Superscripts indicate statistical difference from straight (*), approach stride same condition (a), turn stride same condition (t), and between conditions for the same phase (s). Discussion and conclusions: The present cohort preferred turning using an inside foot strategy regardless of an increased risk of fall and increasedmuscular demand previously reported [4] and decreased stride width found here. However, it remains unclear how other populations, such as childrenwith cerebral palsy, would perform turning maneuvers. Investigation of turning may provide greater insight into the biomechanical adaptations required for independent ambulation and may lead to the development of more functional rehabilitative programs and improved surgical outcomes.