Joint Kinematic Variables Research Articles

A comparison study of myoelectric regression performances when estimating different types of joint kinematic data

Myoelectric control is used in assistive devices such as powered prostheses or exoskeletons, and advances in this area could greatly improve the quality of life for individuals with motor disabilities. Regression machine learning models have been studied to provide a more natural and intuitive control of these devices. Such models have often been applied to estimate joint kinematic variables like angles, angular velocities, and accelerations, with the former receiving considerably more attention in the literature. Despite this prevailing focus, we proposed that employing velocities or accelerations as the target variable of myoelectric regressors instead of angles could lead to better regression performances. To investigate this, our study compares the performance of electromyogram (EMG) regressors in predicting each of these three joint kinematic variables. A comprehensive comparison was conducted, including different regression models, feature extraction methods, conditions, joints, and performance metrics. Overall, the performances of models estimating joint angular velocities or accelerations were consistently superior to those estimating angles. However, the differences between angular velocities and accelerations often were small and lacked statistical significance. These results were observed for most models, features, and conditions, not just the best-performing ones (which were: models = convolutional neural networks; features = waveform length, difference absolute mean value, and Willison amplitude; and conditions = wider and faster movements). Several factors were proposed to explain these findings in the context of current literature, including aspects of the EMG-kinematic signals relationships, kinematic waveform properties, studied movements, and the process for obtaining kinematic variables. Based on the results and discussion, recommendations for future works were made, and areas for further research were suggested, both aiming at improving myoelectric assistive technologies.

The development of an automated assessment system for resistance training movement

ABSTRACT Portable data collection devices and machine learning (ML) have been combined in autonomous movement analysis models for resistance training (RT) movements. However, input features for these models were mostly extracted empirically and subsequent models demonstrated limited interpretability and generalisability to real-world settings. This study aimed to investigate the utility of interpretable and generalisable modelling techniques and several data-driven feature extraction (FE) methods. This was achieved by developing machine learning movement analysis models for the barbell back squat and deadlift using markerless motion capture. 61 participants performed submaximal and maximal repetitions of both RT movements. Movement data was collected using two Azure Kinect cameras. Joint and segment kinematic variables were calculated from the collected depth imaging, and input features were extracted using traditional, manual FE methods and novel data-driven techniques. Classifiers were developed for several predefined technical deviations for both movements. Many of the addressed technical deviations could be classified with good levels of accuracy (≥70%) while the remainder were poor (55%–60%). Additionally, data-driven FE techniques were comparable to previous, traditional FE methods. Interpretable and generalisable modelling techniques can be utilised to good effect for certain classification tasks while data-driven FE techniques did not provide a consistent advantage over traditional FE methods.

Does Anterior Cruciate Ligament Reconstruction with a Hamstring Tendon Autograft Predispose to a Knee Valgus Alignment on Initial Contact during Landing? A Drop Vertical Jump Movement Analysis

The mechanism most correlated with anterior cruciate ligament (ACL) tears is the simultaneous valgus and external rotation of the knee. This study investigated if ACL reconstruction with a hamstring tendon autograft predisposes to “knee-in & toe-out” compared to ACL reconstruction with a patellar tendon autograft and to healthy individuals during a drop vertical jump. A three-dimensional markerless motion capture was used to conduct a case control study, collecting data from 11 healthy participants and 14 participants who underwent ACL reconstruction, 8 with a hamstring tendon autograft and 6 with a patellar tendon autograft, while performing a bilateral drop vertical jump. Joint kinematic variables such as angular positions, moments and velocities were obtained by processing video recordings with the Theia Markerless system and Visual3D. Differences between groups were calculated using the independent Sample T-test and One-Way ANOVA with Bonferroni post hoc adjustments. No significant differences were found at the peak knee valgus for the maximum valgus (mean difference (md): −2.14 ± 1.57 deg, t (23): 0.171, p = 0.187, d = 0.548), rotation (md: 1.04 ± 1.97°, t (23): 0.001, p = 0.601, d = 0.214) and flexion (md: −10.29 ± 11.82°, t (23): 0.917, p = 0.393, d = 0.351) of the knee, when comparing healthy participants with those who underwent ACL reconstruction. Vertical ground reaction forces were significantly higher in the healthy group when compared to the ACL reconstruction group (md: 20.11 ± 6.29 N/kg, t (23): 1.264, p = 0.049, d = 0.836). The knee extension angular moment and angular velocity were significantly higher for the healthy participants, when compared to participants who underwent ACL reconstruction with a patellar tendon autograft (md: 0.65 ± 0.18 Nm/kg, F (2.22): 7.090, p = 0.004, d = 0.804; md: −111.51 ± 38.31°/s, F (2.22): 4.431, p = 0.024, d = 1.000, respectively). ACL reconstruction with a hamstring tendon autograft does not increase the risk of a valgus knee alignment movement on initial contact during landing. Differences found in various parameters may justify the evaluation of the quality movement with a motion capture system while performing the drop vertical jump for the creation of specialized rehabilitation programs.

Effect of freezing of gait and dopaminergic medication in the biomechanics of lower limbs in the gait of patients with Parkinson’s disease compared to neurologically healthy

IntroductionThis study aims to evaluate the effects of medication, and the freezing of gait (FoG) on the kinematic and kinetic parameters of gait in people with Parkinson’s disease (pwPD) compared to neurologically healthy. MethodsTwenty-two people with a clinical diagnosis of idiopathic PD in ON and OFF medication (11 FoG), and 18 healthy participants (control) were selected from two open data sets. All participants walked on the floor on a 10-meter-long walkway. The joint kinematic and ground reaction forces (GRF) variables of gait and the clinical characteristics were compared: (1) PD with FoG (pwFoG) and PD without FoG (pwoFoG) in the ON condition and control; (2) PD with FoG and PD without FoG in the OFF condition and control; (3) Group (PD with FoG and PD without FoG) and Medication. Results(1) FoG mainly affects distal joints, such as the ankle and knee; (2) PD ON showed changes in the range of motion of both distal and proximal joints, which may explain the increase in step length and gait speed expected with the use of L-Dopa; and (3) the medication showed improvements in the kinematic and kinetic parameters of the gait of people with pwFoG and pwoFoG equally; (4) pwPD showed a smaller second peak of the vertical component of the GRF than the control. ConclusionThe presence of FoG mainly affects distal joints, such as the ankle and knee. PD presents a lower application of GRF during the impulse period than healthy people, causing lower gait performances.

Inertial-based gait metrics during turning improve the detection of early-stage Parkinson's disease patients.

Patients with early-stage Parkinson's disease (PD) exhibit various but subtle motor symptoms, especially postural instability and gait disorders (PIGD). Patients show deteriorated gait performance at turns as the complex gait task requires more limb coordination and postural stability control, which may help to discriminate signs of early PIGD. In this study, we firstly proposed an IMU-based gait assessment model for quantifying comprehensive gait variables in both straight walking and turning tasks from five domains: respectively gait spatiotemporal parameters, joint kinematic parameters, variability, asymmetry, and stability. Twenty-one patients with idiopathic Parkinson's disease at the early stage and nineteen age-matched healthy elderly adults were enrolled in the study. Each participant wore a full-body motion analysis system with 11 inertial sensors and walked along a path consisting of straight walking and 180-degree turns at a self-comfortable speed. A total of one hundred and thirty-nine gait parameters were derived for each gait task. We explored the factor effect of group and gait tasks on gait parameters using a two-way mixed analysis of variance. The discriminating ability of gait parameters between PD and the control group was evaluated using receiver operating characteristic analysis. Sensitive gait features were optimally screened (AUC>0.7) and categorized into 22 groups to classify PD and healthy controls based on a machine learning method. Results demonstrated that PD patients exhibited more gait abnormalities at turns, especially on the RoM and stability of the neck, shoulder, pelvic, and hip joints compared to the healthy control group. These gait metrics have good discriminating abilities to identify early-stage PD (AUC>0.65). Moreover, the inclusion of gait features at turns can significantly improve the classification accuracy compared to that only used parameters during straight walking. We show that quantitative gait metrics during turning have great potential to be used for enhancing early-stage PD detection.

Influence of expertise level on techniques of applying top and back spins in cue sports

ABSTRACT This study compared the kinematics of upper body and cue stick among players of various skill levels when performing back spin and top spin shots. Twenty-eight male cue sports players were assigned to the novice (n = 10), intermediate (n = 9), or skilled groups (n = 9). The back spin and top spin tests were administrated while kinematic data were recorded using a 3D motion capture system. The results revealed greater upper limb joint ranges of motions (all p < 0.05), maximum angular velocities (all p < 0.05), and cue tip speed in the back spin than top spin shots (p < 0.001). None of joint kinematic or shot performance variables investigated was significantly different among the three skill levels (all p > 0.05). For the head movement, the novice group exhibited greater anteroposterior displacement than the skilled group (p = 0.020). In conclusion, except for the head movement, the upper body and cue stick kinematics did not significantly differ among players with varied skill levels. Greater joint ranges of motions and angular velocities were required to generate a faster cue tip speed for the back spin shots when compared with the top spin shots.

Task demand and load carriage experience affect gait variability among military cadets

Load carriage is an inevitable daily task for soldiers. The purposes of this study were to explore the extent to which gait variability (GV) is affected by load carriage and experience among military cadets, and whether experience-related differences in GV are dependent on task demand. Two groups of cadets (30 experienced, 30 less experienced) completed a load carriage task in each of three load conditions (no load, 16 kg, 32 kg). Three categories of GV measures were obtained: spatiotemporal variability, joint kinematic variability, and Lyapunov exponents. Compared to traditional mean gait measures, GV measures were more discriminative of experience: although both groups showed similar mean gait measures, the experienced participants had reduced variability in spatiotemporal measures (p ≤ 0.008) and joint kinematics (p ≤ 0.004), as well as lower levels of long-term local dynamic stability at the ankle (p = 0.040). In both groups, heavier loads were also caused increased GV (p ≤ 0.018) and enhanced short-term local dynamic stability at the knee (p = 0.014). These results emphasize the importance of GV measures, which may provide a more complete description of adaptability, stability, and control; highlight alternate movement strategies during more difficult load carriage; and capture experience-related differences in load carriage strategies.

Movement Variability and Loading Characteristics in Athletes With Athletic Groin Pain: Changes After Successful Return to Play and Compared With Uninjured Athletes.

Athletic groin pain (AGP) can lead to altered movement patterns during rapid deceleration and acceleration. However, the effect of AGP on movement variability and loading patterns during such actions remains less clear. To investigate, using a continuous lateral hurdle hop task, how movement variability and magnitude measures of 3-dimensional (3D) kinematic, kinetic, and vertical ground-reaction force (vGRF) variables are (1) affected by AGP (AGP vs uninjured controls [CON]) and (2) changed after successful rehabilitation (AGP prerehabilitation vs AGP postrehabilitation vs CON). Controlled laboratory study. A total of 36 athletes diagnosed with AGP and 36 uninjured CON athletes matched on age (18-35 years), level (subelite), and type of sports played (multidirectional field sport) performed a continuous lateral hurdle hop test that involved 10 side-to-side hops over a 15-cm hurdle. The 3D joint kinematic, kinetic, and vGRF variables (total, eccentric, and concentric; ground contact time, peak force, and impulse; and eccentric rate of force development) were examined. The AGP and CON groups were tested at baseline, and the AGP group was retested after participants successfully completed a standardized, exercise-based rehabilitation program targeting intersegmental control. There were no differences in baseline characteristics between the AGP (mean ± SD: age, 27.5 ± 4.8 years; height, 179.8 ± 6.3 cm; mass, 80.3 ± 7.1 kg) and CON (mean ± SD: age, 24.1 ± 4.5 years; height, 181.0 ± 5.8 cm; mass, 80.4 ± 8.2 kg) groups. At baseline, athletes with AGP demonstrated altered loading patterns in the vGRF (longer ground contact times, reduced peak force, and reduced rate of force development) compared with CON athletes, while no significant difference in any movement variability variables was evident. After rehabilitation, the athletes with AGP demonstrated significant changes in transverse and coronal plane hip and trunk kinematics, with no significant differences in vGRF variables compared with the CON group. The differences in baseline vGRF measures between the AGP and CON groups were no longer evident after athletes with AGP underwent rehabilitation. No differences in movement variability were evident between the AGP and CON groups, either before or after rehabilitation. Rehabilitation programs should consider targeting intersegmental hip and trunk movement patterns to positively influence loading patterns in athletes with AGP.

Detecting side-to-side differences of lower limb biomechanics during single-legged forward landing after anterior cruciate ligament reconstruction

BackgroundMotion analysis can be used to evaluate functional recovery after anterior cruciate ligament (ACL) reconstruction; however, the biomechanics parameters of the lower limb that are specifically altered in ACL-reconstructed knees compared to the contralateral side are not well understood. This retrospective study aimed to compare side-to-side differences in lower limb biomechanics during the first 100 milliseconds (ms) after initial contact in a single-leg forward landing task. MethodsUsing three-dimensional motion analysis, lower joint kinematic and kinetic variables were measured 8–10 months postoperatively in 22 patients who had undergone ACL reconstruction. We determined side-to-side differences in lower limb biomechanics over the 100-ms timeframe after landing, and receiver operating characteristic (ROC) curve analyses were performed to calculate the area under the curve (AUC) for parameters showing significant side-to-side differences. ResultsDuring the 100-ms timeframe after landing, 58 kinematic and kinetic items showed significant side-to-side differences. Side-to-side differences in lower limb biomechanics over the 40-ms timeframe after landing existed. The ROC curve analysis identified 11 items with AUC values ≥ 0.70, including hip flexion, abduction moment, and knee joint power, and their AUC values were not significantly different. ConclusionHip flexion/abduction moment and knee power after GRF max could be used as outcomes for assessing functional recovery in patients who have undergone ACL reconstruction.

Effects of Age and Attentional Focus on the Performance and Coordination of the Sit-to-Stand Task

This study investigated whether age and attentional focus affect synergy organization of sit-to-stand (STS). Young and older adults performed STS while holding a cup under internal (IF) and external focus (EF) instructions. Uncontrolled manifold analysis was used to decompose trial-to-trial variability in joint kinematics into variability that preserves (VUCM) and interferes (VORT) with the horizontal and vertical positions of the center of mass (CoM) and cup. VUCM was significantly higher than VORT for all variables in both age groups and focus conditions. Older adults demonstrated higher VUCM for all variables and higher VORT for all variables except the vertical position of the cup. IF instructions benefited older adults, leading to decreased VORT of the vertical position of CoM and horizontal and vertical positions of the cup.

Bow-Side Kinematics Studies in Violinists: An Experimental Design Tracking Intra- and Inter-Musician Variability by Bow Stroke, String Played, and Tempo.

Comparison of bow-side kinematics in violinists is hindered by the scarcity of studies available. This makes meta-analysis impossible. This paper assesses the effect of music-based variables (bow stroke, tempo, and string played) on intra- and inter-participant variability in joint kinematics. The joint kinematics of nine high-level violinists were acquired via a motion capture system while they played a standardized piece of music involving contrasting bow strokes and strings at different tempi. Results were compared using linear mixed models using the root mean square (RMS) for each joint. We found highly individualized patterns of play, deduced from a low intra- but high inter-musician variability (4.2° vs 13.1° of normalized RMS) in joint kinematics. String played and bow stroke had the greatest effect on joint kinematics. The string played had the greatest impact on shoulder kinematics, and the bow stroke had the greatest impact on elbow and wrist kinematics. Based on these results, we propose guidelines for future research designed to study bow kinematics in the field of biomechanics of violin movements. For ease of comparison between studies and to limit the time and resources required, our main suggestions are to use repeated measures designs with a legato reference condition and to choose pieces of music spanning multiple strings.

Kinematics predictors of spatiotemporal parameters during gait differ by age in healthy individuals

Joint biomechanics and spatiotemporal gait parameters change with age or disease and are used in treatment decision-making. Research question: To investigate whether kinematic predictors of spatiotemporal parameters during gait differ by age in healthy individuals. Methods: We used an open dataset with the gait data of 114 young adults (M = 28.0 years, SD = 7.5) and 128 older adults (M = 67.5 years, SD = 3.8) walking at a comfortable self-selected speed. Linear regression models were developed to predict spatiotemporal parameters separately for each group using joint kinematics as independent variables. Results: In young adults, knee flexion loading response and hip flexion/extension were the common predictors of gait speed; hip flexion and hip extension contributed to explaining the stride length; hip flexion contributed to explaining the cadence and stride time. In older adults, ankle plantarflexion, knee flexion loading response, and pelvic rotation were the common predictors of the gait speed; ankle plantarflexion and knee flexion loading response contributed to explaining the stride length; ankle plantarflexion loading response and ankle plantarflexion contributed to explain the cadence, stride width and stride time. Significance: Our results suggest that the ability of joint kinematic variables to estimate spatiotemporal parameters during gait differs by age in healthy individuals. Particularly in older adults, ankle plantarflexion was the common predictor of the spatiotemporal parameters, suggesting the importance of the ankle for gait parameters in this age group. This provides insight for clinicians into the most effective evaluation and has been used by physical professionals in prescribing the most appropriate exercises to attenuate the effects produced by age-related neuromuscular changes.

Influence of metatarsophalangeal joint stiffness on take-off performances and lower-limb biomechanics in jump manoeuvres

ABSTRACT Forefoot and toes are prominent regions for locomotion and individual metatarsophalangeal joint (MTPJ) stiffness may be linked to jump take-off mechanics and performances. However, little is known about the relationships between MTPJ stiffness and take-off related variables. This study examined the relationship between individual MTPJ stiffness and biomechanical variables under various vertical countermovement jumps (CMJ) conditions. We measured MTPJ stiffness on 21 male university basketball players and then asked them to perform jumps under single, consecutive and running CMJ conditions. Pearson’s correlation coefficient was employed to examine the relationships between MTP passive stiffness and each jumping performance, ground reaction force (GRF) and joint kinematic and kinetic variables. The results indicated that MTPJ stiffness significantly correlated with maximum jump height (r = 0.49, moderate), peak take-off velocity (r = 0.47, moderate), peak take-off ankle plantarflexion moment (r = 0.68, strong), peak dorsiflexion moment (r = 0.60, strong) and peak take-off ankle power (r = 0.44, moderate) in consecutive CMJ. Only a moderate correlation between MTPJ stiffness and peak MTPJ extension take-off velocity (r = −0.46, moderate) was determined in a single CMJ. There were no significant correlations found in running CMJ conditions. These findings imply that higher MTPJ stiffness of participants was related to improved jump performances in consecutive jumps.

Biological Sex-Related Differences in Glenohumeral Dynamics Variability during Pediatric Manual Wheelchair Propulsion.

Shoulder pain and pathology are extremely common in adult manual wheelchair users with spinal cord injury (SCI). Within this population, biological sex and variability in shoulder joint dynamics have been shown to be important contributors to both shoulder pain and pathology. Sex-related differences in shoulder dynamics variability during pediatric manual wheelchair propulsion may influence a user's lifetime risk of shoulder pain and pathology. The purpose of this study was to assess the influence of biological sex on variability in three-dimensional (3-D) glenohumeral joint dynamics in pediatric manual wheelchair users with SCI. An inverse dynamics model computed 3-D glenohumeral joint angles, forces, and moments of 20 pediatric manual wheelchair users. Levene's tests assessed biological sex-related differences in variability. Females exhibited less variability in glenohumeral joint kinematics and forces, but greater variability in joint moments than males. Evaluation of glenohumeral joint dynamics with consideration for biological sex and variability strengthens our interpretation of the relationships among shoulder function, pain, and pathology in pediatric manual wheelchair users.Clinical Relevance- Female pediatric manual wheelchair users may be at an increased risk of shoulder repetitive strain injuries due to decreased glenohumeral joint motion and force variability during propulsion. This work establishes quantitative methods for determining the effects of biological sex on the variability of shoulder joint dynamics.

Effects of foot progression angle on knee mechanics during an anticipated cutting task: A statistical parametric mapping approach

Cutting is considered a “high-risk” movement for anterior cruciate ligament (ACL) injuries. It has been established that sex differences exist during cutting, placing females at greater ACL injury risk. Foot progression angle (FPA) during landing has been shown to influence lower extremity mechanics, yet little is known how FPA influences mechanics during cutting. The purpose of this study was to compare two FPA conditions during cutting between males and females. Twenty-four males and females were tested using two FPA conditions: toe-in 15° (TI15) and toe-out 15° (TO15). Right knee joint kinematic and kinetic variables were measured using a motion capture system and force plate. Five successful trials were collected and compared between FPA conditions. One-dimensional statistical parametric mapping was used to assess changes in knee mechanics between males and females over the entire stance phase. The only sex × FPA effect found was knee flexion angle. Females cutting at TI15 had decreased knee flexion angle compared TO15 (p = 0.019). Significant sex main effects included knee abduction and rotation angles, and knee flexion and rotation moments. Significant FPA main effects included knee flexion, abduction and rotation angles. The results show cutting with a toe-in FPA of 15° is enough to induce changes in knee abduction angle while cutting with 15° toe-out FPA influenced knee flexion and rotation angles. These data suggest that different cutting FPAs may be influential on known ACL injury risk variables. However, more research is warranted on cutting FPA before FPA is targeted as part of ACL injury prevention protocols.

Kinematic factors associated with start performance in World-class male sprinters

The aim was to investigate the kinematic factors associated with successful performance in the initial acceleration phase of a sprint in the best male athletes in the World at the 2018 World Indoor Athletics Championships. High speed video (150 Hz) was captured for eight sprinters in the men’s 60 m final. Spatio-temporal and joint kinematic variables were calculated from the set position to the end of the first ground contact post-block exit (GC1). Normalised average horizontal external power (NAHEP) defined performance and was the dependent variable for a series of regression analyses. Clear relationships were found between GC1 NAHEP and 10-m time, 60-m time, change in velocity, acceleration and contact time in the first ground contact (r = –0.74, –0.64, 0.96, 0.91 and –0.56, respectively). Stepwise multiple linear regression of joint kinematic variables in the first ground contact revealed that trunk angle at take-off and thigh separation angle at take-off explained nearly 90% of variation in GC1 NAHEP (R2 = 0.89). The athletes’ projection at take-off with a forward leaning trunk and large thigh separation is characteristic therefore of excellent initial acceleration performance and this will be a good visual guide for technical coaching instruction. This was the first study of its kind to adopt such a research design in a World-class sample in a representative environment. Future studies that combine detailed kinematic and kinetic data capture and analysis in such a setting will add further insight to the findings of this investigation.

Jumping with barbell load: Assessment of lower limb joint kinematics and kinetics during landing

Loaded jumps are commonly used to improve leg muscle power. However, the additional load during jump-landing might increase the potential for overuse injury. Therefore, the aims of this study were to evaluate the effect that barbell load has on lower limb joint kinematics and kinetics during jump-landing and to evaluate the effect of arresting the barbell load at flight apex prior to landing on joint kinematic and kinetic variables. Barbell-loaded squat jumps (20, 40, and 60 kg) were investigated during two jump-landing conditions: 1) barbell-loaded (landing with barbell load) and 2) barbell-arrested (barbell load arrested at flight apex prior to jump-landing). Lower body kinematics and joint kinetics were assessed during jump-landing. In the barbell-loaded jump-landing condition, joint angles at initial contact decreased with increasing barbell load. Knee and hip peak power decreased (knee: −38%; hip: −46%), while ankle joint work increased with increasing barbell load. Joint moments, powers and work were decreased in the barbell-arrested condition compared to the barbell-loaded condition. Barbell-loaded jump-landings do not pose increased demands on the knee and the hip joint compared to bodyweight only jump-landings, due to the load-based reductions in jump height and joint kinematic adaptions. However, ankle joint contribution in energy dissipation is increased, possibly resulting in an increased overuse injury risk at this joint. Arresting the barbell load at flight apex prior to jump-landing substantially reduces the joint kinetics, hence serving as valuable training tool for athletes returning to sport after injuries.

Toe-out gait decreases knee load during stair descent in healthy individuals

IntroductionBoth toe-out (TO) and toe-in (TI) gaits decrease knee load during walking and stair ascent. However, few reports have focused on stair descent, which requires a higher load compared with walking. ObjectivesThe purpose of this study was to investigate the effect of foot progression angle (FPA) on knee joint load and related variables during stair descent. MethodsTwenty-two healthy young adults performed a stair descent task at a predefined speed of 90 steps/min with normal gait, TO gait (15° > normal), and TI gait (15° < normal). 3D motion analysis was conducted. In addition, the ground reaction force (GRF) with 3 components, center of pressure (COP) positions, and sagittal and frontal plane hip and knee joint kinematic and kinetic variables were recorded during stair descent. ResultsThe medial GRF increased, and the COP position was more lateral in TO gait compared with normal and TI gait during stair descent. TO gait exhibited a significant decrease in the peak knee adduction moment by ∼20% compared with normal gait and by ∼23% compared with TI gait. In addition, the knee flexion moment in TI gait significantly increased compared with normal and TO gait. ConclusionsTO gait decreases knee joint load during stair descent. Our results might have important implications for patients with knee osteoarthritis (OA) or those at risk of developing knee OA. Moreover, it will be of great interest to those involved in the research or clinical practice dealing with the role of gait in pathologic conditions, such as OA.

Running speed does not influence the asymmetry of kinematic variables of the lower limb joints in novice runners

The purpose of this study was to evaluate kinematic variables at 5 running speeds (8 to 12 km/h), for the asymmetry between lower limbs. We also investigated the effects of running speed on the bilateral asymmetry of the lower limb joints kinematic variables among novice runners. Kinematic (200 Hz) running data were collected bilaterally for 17 healthy male novice runners (age: 23.1 ± 1.3 years, height: 1.77 ± 0.04 m, mass: 72.3 ± 4.57 kg, BMI: 23.1 ± 1.0 kg/m2) running on a treadmill at 5 fixed speeds (8, 9, 10, 11 and 12 km/h) in a randomized order. Symmetry angles (SA) were calculated to quantify gait asymmetry magnitude at each running speed. Overall, SPM analysis using paired t-tests revealed significant joints kinematic differences between the left lower limb and the right lower limb at each running speed. Significant differences between limbs were found for all joint kinematic variables in the ankle and hip, regardless of running speed. As for the knee angle, significant differences between legs were only found during the running speed of 11 km/h. For knee angle velocity, significant differences between legs were found in all running speeds except for 8 km/h. However, there was no noticeable difference in asymmetry values across running speeds. The findings of the current study indicate that gait asymmetry of joint kinematics variables between lower limbs during running is apparent in healthy novice runners. Meanwhile, running speed does not influence lower limb joints kinematic asymmetry among novice runners.

The trunk’s contribution to postural control under challenging balance conditions

BackgroundThe double inverted pendulum model is imprecise when applied to studies of postural control. Although multijoint analyses have improved our understanding of how balance is maintained, the exact role of the trunk remains unclear. Research questionsWhat is the trunk’s contribution in postural control with respect to the other joints and how do trunk muscles control trunk kinematics? MethodsThirty-six healthy athletes (handball, karate, long jump) performed a highly challenging balance task while the ground support was dynamically tilted in the sagittal plane. The center of force (CoF) as well as lower limb joint angles and the trunk-pelvis angle were respectively measured with a force platform and inertial measurement units. The amplitude, sway path and standard deviation of the CoF and the joint angles were then calculated. Electromyography was used to record the activity of the rectus abdominis, external obliquus, and erector spinae muscles. Multiple linear regressions were computed to determine the joints’ and muscles’ contributions (β-coefficients) in predicting CoF variables and trunk kinematics, respectively. ResultsThe linear combination of joint kinematic variables accounted for between 33 % and 75 % of the variance in the CoF. The ankle had the highestβ and was a significant predictor of all CoF variables. The trunk yielded the second highest β-coefficient and was a significant predictor of the CoF sway path. Electromyography variables accounted for no more than 35 % of the variance in the trunk kinematics, and erector spinae activity was the only significant predictor. SignificanceThe trunk appears to be the second most important element during this specific postural task, in the magnitude of body sway in particular. But neuromuscular control of these trunk processes is difficult to characterize with surface electromyography only. The trunk should be taken into account when seeking to improve overall postural control (e.g. during training, rehabilitation).