Motor patterns of patients with spinal muscular atrophy suggestive of sensory and corticospinal contributions to the development of locomotor muscle synergies.

Complex locomotor patterns are generated by combination of muscle synergies. How genetic processes, early sensorimotor experiences, and the developmental dynamics of neuronal circuits contribute to the expression of muscle synergies remains elusive. We shed light on the factors that influence development of muscle synergies by studying subjects with spinal muscular atrophy (SMA, types II/IIIa), a disorder associated with degeneration and deafferentation of motoneurons and possibly motor cortical and cerebellar abnormalities, from which the afflicted would have atypical sensorimotor histories around typical walking onset. Muscle synergies of children with SMA were identified from electromyographic signals recorded during active-assisted leg motions or walking, and compared with those of age-matched controls. We found that the earlier the SMA onset age, the more different the SMA synergies were from the normative. These alterations could not just be explained by the different degrees of uneven motoneuronal losses across muscles. The SMA-specific synergies had activations in muscles from multiple limb compartments, a finding reminiscent of the neonatal synergies of typically developing infants. Overall, while the synergies shared between SMA and control subjects may reflect components of a core modular infrastructure determined early in life, the SMA-specific synergies may be developmentally immature synergies that arise from inadequate activity-dependent interneuronal sculpting due to abnormal sensorimotor experience and other factors. Other mechanisms including SMA-induced intraspinal changes and altered cortical-spinal interactions may also contribute to synergy changes. Our interpretation highlights the roles of the sensory and descending systems to the typical and abnormal development of locomotor modules.NEW & NOTEWORTHY This is likely the first report of locomotor muscle synergies of children with spinal muscular atrophy (SMA), a subject group with atypical developmental sensorimotor experience. We found that the earlier the SMA onset age, the more the subjects' synergies deviated from those of age-matched controls. This result suggests contributions of the sensory/corticospinal activities to the typical expression of locomotor modules, and how their disruptions during a critical period of development may lead to abnormal motor modules.

Tracking Bilateral Lower Limb Kinematics of Distance Runners on Treadmill Using a Single Inertial Measurement Unit.

Distance running related injuries are common, and many ailments have been associated with faulty posture. Conventional measurement of running kinematics requires sophisticated motion capture system in laboratory. In this study, we developed a wearable solution to accurately predict lower limb running kinematics using a single inertial measurement unit placed on the left lower leg. The running data collected from participants was used to train a model using long short-term memory (LSTM) neural networks with an inter-subject approach that predicted lower limb kinematics with an average accuracy of 80.2%, 85.8%, and 69.4% for sagittal hip, knee and ankle joint angles respectively for the ipsilateral limb. A comparable accuracy range was observed for the contralateral limb. The average RMSE (root mean squared error) of sagittal hip, knee and ankle were 8.76°, 13.13°, and 9.67° respectively for the ipsilateral limb. Analysis of contralateral limb kinematics was performed. The model established in this study can be used as a monitoring device to track essential running kinematics in natural running environments. Besides, the wearable solution can be an integral part of a real-time gait retraining biofeedback system for injury prevention and rehabilitation.

Effect of surface inclination on vertical loading rate and footstrike pattern in trail and road runners.

Trail runners have been reported to be more injury prone than road runners. Limited past studies have examined the difference in the running biomechanics between the two groups of runners. More importantly, the effect of surface inclination has not been fully investigated. Hence, this study examined the effect of surface inclination on running biomechanics in trail and road runners. Twenty trails and 20 road runners were recruited in this study. Trail runners appeared to be more experienced and had longer training distance per week (p < 0.001) compared to road runners. All participants ran at a self-selected pace on an instrumented treadmill in three inclination conditions (i.e., level, +10% uphill and -10% downhill) in a random order. Vertical average loading rate (VALR), vertical instantaneous loading rate (VILR) and footstrike angle (FSA) were measured using established methods. Trail runners experienced greater VILR (p = 0.039, Cohen's d = 2.9) with a greater FSA (p = 0.002, Cohen's d = 1.1) during downhill running than road runners. No significant differences in VALR, VILR and FSA were found between the two groups during level and uphill running. Our findings provide potential biomechanical rationale to explain a higher injury incidence among trail runners.

Evaluation of a Restoration Algorithm Applied to Clipped Tibial Acceleration Signals.

Wireless accelerometers with various operating ranges have been used to measure tibial acceleration. Accelerometers with a low operating range output distorted signals and have been found to result in inaccurate measurements of peaks. A restoration algorithm using spline interpolation has been proposed to restore the distorted signal. This algorithm has been validated for axial peaks within the range of 15.0-15.9 g. However, the accuracy of peaks of higher magnitude and the resultant peaks have not been reported. The purpose of the present study is to evaluate the measurement agreement of the restored peaks using a low-range accelerometer (±16 g) against peaks sampled using a high-range accelerometer (±200 g). The measurement agreement of both the axial and resultant peaks were examined. In total, 24 runners were equipped with 2 tri-axial accelerometers at their tibia and completed an outdoor running assessment. The accelerometer with an operating range of ±200 g was used as reference. The results of this study showed an average difference of -1.40 ± 4.52 g and -1.23 ± 5.48 g for axial and resultant peaks. Based on our findings, the restoration algorithm could skew data and potentially lead to incorrect conclusions if used without caution.

Reliability of Ultrasound Imaging in Examining Integrity and Inflammation in the Dorsalis Pedis Artery.

OBJECTIVE: Assessment of small vessel inflammatory diseases such as rheumatoid vasculitis is challenging. Small arteries such as the dorsalis pedis artery (DPA) are difficult to assess for changes in the arterial wall with medical imaging. Ultrasound imaging is a viable tool for examining the integrity and inflammatory changes in the arterial wall; however, no empirical data on its reliability have been described. METHODS: We measured the intra- and inter-rater reliability of ultrasound measurements across five parameters evaluating arterial integrity of the proximal DPA in participants with and without small vessel disease. We recruited 10 participants with rheumatoid arthritis and 10 healthy controls. Two sonographers using ultrasound independently measured DPA lumen diameter, artery diameter, lumen-to-arterial diameter ratio, arterial Doppler velocity and inflammatory changes in the proximal wall of the DPA. The intraclass correlation coefficient (ICC) was used to evaluate 95% confidence intervals within and between raters. Bland-Altman analyses were used to assess limits of agreement and were compared with minimal clinically important differences (MCID). RESULTS: Four of five selected parameters were found to have excellent intra- and inter-rater reliability within and between raters (ICC = 0.903-0.996). Acceptable reliability was found for measurement of arterial blood flow velocity within raters (ICC = 0.815-0.909), but not between raters (ICC = 0.634). Standard mean errors in all parameters were within minimal clinically important differences. CONCLUSION: Ultrasound imaging has been found to be a reliable method of assessment of arterial integrity and inflammation of the proximal DPA in people with small vessel disease. Evaluation of arterial blood flow velocity requires cautious interpretation.

Personal belief on elastic tape and tape tension affect perceived performance, but not muscle activity and endurance.

BACKGROUND: Previous studies reported inconsistent outcomes on elastic taping for three potential reasons: 1) poor control of placebo effect; 2) no consensus regarding the optimal tape tension; and 3) lack of investigation on muscle endurance, as the proposed tape recoiling force may not promote peak force generation but exert a consistently low force and improve submaximal contraction. PURPOSE: This study compared the effects of elastic tape and its tension on muscle activity and endurance in people with extremely positive and negative personal belief on elastic tape. METHODS: Using a validated instrument, we identified 20 participants with extremely positive personal belief on elastic tape (+ belief), and 20 with extremely negative personal belief (- belief). They performed wrist isometric endurance tests under three taping conditions (i.e. no tape, 50%, and 100% tension). We measured isometric wrist extensor muscle endurance, electromyography muscle activity, and self-perceived performance for each condition. RESULTS: The differences between the two groups in isometric muscle endurance (p = .85) and muscle activity (p = .53) were not statistically significant, regardless of tape conditions. However, participants with + belief reported better perceived performance than those with - belief (p < .001, partial eta squared = 0.70). Specifically, 100% tape tension yielded stronger self-perceived performance than 50% tension (Cohen's d = 0.91) and no tape (Cohen's d = 1.86). On the other hand, participants with - belief perceived similar performance across tape tensions (p = .55). CONCLUSION: Elastic tape does not modulate muscle activity and enhance muscle endurance. People with a strong positive personal belief on elastic tape may perceive a better performance with a greater tape tension.

The influence of running shoes on familiarization time for treadmill running biomechanics evaluation.

This study investigated treadmill familiarisation time in different shoe conditions by comparing lower limb consecutive kinematics waveforms using a trend symmetry method to calculate trend symmetry index, range amplitude ratio and range offset. Eighteen young adults (26.6 ± 3.3 years, 7 females) completed three 10-minute running trials at their preferred running speed (2.30 ± 0.17 m/s) on a treadmill with three shoe conditions (i.e., usual, minimalist and maximalist shoes) in a random order. Sagittal lower limb kinematic data were recorded using inertial measurement units. The results showed that sagittal-plane kinematic waveforms in the hip, knee and ankle remained consistent (trend symmetry > 0.95) without extreme excursions (range amplitude ratio ≈ 1) over 10 minutes within each testing shoe condition. Significant time × shoe interaction effect was observed in range offset (i.e., absolute differences in the average degree of kinematic waveforms between consecutive minutes) at ankle (p = 0.029, ŋp2 = 0.096) and knee (p = 0.002, ŋp2 = 0.126). Post-hoc analysis suggested that running with novel shoes required a shorter time to achieve stable lower limb kinematics (2 to 3 minutes) compared with usual shoes (7 minutes). In conclusion, young healthy adults need up to 3 and 7 minutes to familiarise to the treadmill when running at their preferred speed with their novel and usual running shoes.

Footstrike angle cut-off values to classify footstrike pattern in runners.

Footstrike angle (FSA) has been widely used to classify footstrike pattern (FSP). However, inconsistent FSA cut-off values were adopted in previous studies. This study aimed to validate the FSA cut-off values in runners. Stride index, the gold standard to determine FSP, and FSA were obtained when 15 experienced runners, 14 novice runners and 14 untrained individuals performed 3-min run on an instrumented treadmill at their preferred running speeds in habitual, rearfoot, midfoot and forefoot strike patterns. According to the receiver operating characteristic curve associated with the Youden index, the optimal FSA cut-off values were -0.8° (i.e., cut-off angle for forefoot strike) -7.4° (i.e., cut-off angle for rearfoot strike) for runners. We observed minor differences in the FSA cut-off values across runners with various running experience and a wider cut-off range for midfoot strikers when a modified strike index was utilized. This validation study established cut-off footstrike angles for runners' FSP classification.

Age-Related Modifications of Muscle Synergies and Their Temporal Activations for Overground Walking.

Healthy ageing modifies neuromuscular control of human overground walking. Previous studies found that ageing changes gait biomechanics, but whether there is concurrent ageing-related modulation of neuromuscular control remains unclear. We analyzed gait kinematics and electromyographic signals (EMGs; 14 lower-limb and trunk muscles) collected at three speeds during overground walking in 11 healthy young adults (mean age of 23.4 years) and 11 healthy elderlies (67.2 years). Neuromuscular control was characterized by extracting muscle synergies from EMGs and the synergies of both groups were k -means-clustered. The synergies of the two groups were grossly similar, but we observed numerous cluster- and muscle-specific differences between the age groups. At the population level, some hip-motion-related synergy clusters were more frequently identified in elderlies while others, more frequent in young adults. Such differences in synergy prevalence between the age groups are consistent with the finding that elderlies had a larger hip flexion range. For the synergies shared between both groups, the elderlies had higher inter-subject variability of the temporal activations than young adults. To further explore what synergy characteristics may be related to this inter-subject variability, we found that the inter-subject variance of temporal activations correlated negatively with the sparseness of the synergies in elderlies but not young adults during slow walking. Overall, our results suggest that as humans age, not only are the muscle synergies for walking fine-tuned in structure, but their temporal activation patterns are also more heterogeneous across individuals, possibly reflecting individual differences in prior sensorimotor experience or ageing-related changes in limb neuro-musculoskeletal properties.

Effectiveness of gait retraining interventions in individuals with hip or knee osteoarthritis: A systematic review and meta-analysis.

BACKGROUND: Osteoarthritis is a chronic synovial joint disease leading to pain, stiffness, and gait dysfunction, resulting in a significant health and economic burden. Gait retraining strategies and tools are used to address biomechanical gait dysfunction and symptoms in individuals with osteoarthritis. However, there is limited evidence relating to their effectiveness. QUESTION: Do gait retraining strategies and tools improve gait biomechanics and symptoms in individuals with hip or knee osteoarthritis compared to control or alternate intervention? METHODS: Seven databases were searched using key words relating to osteoarthritis, gait retraining, and biomechanics. A best evidence synthesis was conducted on included studies. Where available, a meta-analysis was performed, and the standardised mean difference (SMD) and 95% confidence internals (CI) were reported. RESULTS: Eighteen studies were included. One study investigated gait retraining in participants with hip osteoarthritis and demonstrated limited evidence for improving gait biomechanics. Seventeen studies on knee osteoarthritis were included in the best evidence synthesis with six included in the meta-analysis. Gait retraining strategies which incorporated a real-time biofeedback tool, appear to have strong evidence for effectively modifying walking biomechanics. Moderate evidence was identified to support kinesiology taping improving pain scores. The meta-analysis pooled effect demonstrated significant improvements for knee adduction moment [SMD, -1.10; 95% CI. -1.85, -0.35] and the Western Ontario and McMaster Osteoarthritis Index in favour of gait retraining than a control intervention [SMD, -0.86; 95% CI. -1.33, -0.39]. All other interventions demonstrated evidence that was conflicting, limited, or not in favour of gait retraining. CONCLUSION: Gait retraining may be beneficial for improving biomechanics and symptoms in knee osteoarthritis, however due to the high heterogeneity and limited studies in the analysis, further research is required. Further high quality randomised controlled trials for knee and especially hip osteoarthritis investigating the effects of gait retraining on biomechanics and symptoms are required.

Strike index estimation using a convolutional neural network with a single, shoe-mounted inertial sensor.

Strike index is a measurement of the center of pressure position relative to the foot length, and it is regarded as a gold standard in classifying strike pattern in runners. However, strike index requires sophisticated laboratory equipment, e.g., force plates and optical motion capture. We present a method of estimating strike index using data from a shoe-mounted inertial measurement unit (IMU) analyzed by a participant-independent convolutional neural network (CNN), which consists of convolutional, max-pooling, and fully-connected layers. To promote data variability, 16 participants were required to land with three strike patterns (rearfoot, midfoot, and forefoot strike) while running on an instrumented treadmill in four conditions i.e., two footwear types and two running speeds. Using the proposed approach, strike index was estimated with a root mean square error of 6.9% and a R2 of 0.89. Training and testing the model with different variations of the data collected showed that the model was robust to changes in speed. The proposed approach enables accurate estimation of strike index outside of traditional gait laboratories. This solution potentially improves running performance and reduces injury risk in distance runners.

Gait difference between children aged 9 to 12 with and without potential depressive mood.

BACKGROUND: It has been reported that depression has an impact on both temporal spatial parameters and walking kinematics in adults. Given the difference in the walking biomechanics between adults and children, this study aimed to compare the gait difference in children aged 9-12 with and without potential depressive mood (PDM). METHODS: 49 children were recruited from local primary schools. We measured participants' depression level using Depression Anxiety Stress Scale (DASS) and classified them into control (i.e., DASS depression subscale score = 0.6 ± 1.4; n = 23) or PDM group (i.e., DASS depression subscale score = 21.3 ± 5.3; n = 26). Video gait analysis was employed to assess temporal spatial parameters and sagittal plane kinematics during self-paced overground walking. Independent t tests or Mann-Whitney tests were used to compare the gait parameters between the two groups. RESULTS: Participants exhibited similar gait speed, vertical oscillation of the centre of mass, stance time, swing time, step length, upper and lower limb kinematics between the two groups (p > 0.05). However, children with PDM displayed a greater head flexion than controls (p = 0.026; Cohen's d = 0.66; moderate effect). SIGNIFICANCE: Children with PDM may present a more slumped posture during walking when compared with their counterparts. This kinematics difference can potentially be used as a biomechanical marker for detection of mood problems in this cohort.

Sensor-Based Gait Retraining Lowers Knee Adduction Moment and Improves Symptoms in Patients with Knee Osteoarthritis: A Randomized Controlled Trial.

The present study compared the effect between walking exercise and a newly developed sensor-based gait retraining on the peaks of knee adduction moment (KAM), knee adduction angular impulse (KAAI), knee flexion moment (KFM) and symptoms and functions in patients with early medial knee osteoarthritis (OA). Eligible participants (n = 71) with early medial knee OA (Kellgren-Lawrence grade I or II) were randomized to either walking exercise or gait retraining group. Knee loading-related parameters including KAM, KAAI and KFM were measured before and after 6-week gait retraining. We also examined clinical outcomes including visual analog pain scale (VASP) and Knee Injury and Osteoarthritis Outcome Score (KOOS) at each time point. After gait retraining, KAM1 and VASP were significantly reduced (both Ps < 0.001) and KOOS significantly improved (p = 0.004) in the gait retraining group, while these parameters remained similar in the walking exercise group (Ps ≥ 0.448). However, KAM2, KAAI and KFM did not change in both groups across time (Ps ≥ 0.120). A six-week sensor-based gait retraining, compared with walking exercise, was an effective intervention to lower medial knee loading, relieve knee pain and improve symptoms for patients with early medial knee OA.

Self-selected running gait modifications reduce acute impact loading, awkwardness, and effort.

Impact loading has been associated with running-related injuries, and gait retraining has been suggested as a means of reducing impact loading and lowering the risk of injury. However, gait retraining can lead to increased perceived awkwardness and effort. The influence of specifically trained and self-selected running gait modifications on acute impact loading, perceived awkwardness and effort is currently unclear. Sixteen habitual rearfoot/midfoot runners performed forefoot strike pattern, increased step rate, anterior trunk lean and self-selected running gait modifications on an instrumented treadmill based on real-time biofeedback. Impact loading, perceived awkwardness and effort scores were compared among the four gait retraining conditions. Self-selected gait modification reduced vertical average loading rate (VALR) by 25.3%, vertical instantaneous loading rate (VILR) by 27.0%, vertical impact peak (VIP) by 16.8% as compared with baseline. Forefoot strike pattern reduced VALR, VILR and peak tibial acceleration. Increased step rate reduced VALR. Anterior trunk lean did not reduce any impact loading. Self-selected gait modification was perceived as less awkward and require less effort than the specifically trained gait modification (p < 0.05). These findings suggest that self-selected gait modification could be a more natural and less effortful strategy than specifically trained gait modification to reduce acute impact loading, while the clinical significance remains unknown.

How Foot Progression Angle Affects Knee Adduction Moment and Angular Impulse in Patients With and Without Medial Knee Osteoarthritis: A Meta-Analysis.

OBJECTIVE: To investigate effects of foot progression angle (FPA) modification on the first and second peaks of external knee adduction moment (EKAM) and knee adduction angular impulse (KAAI) in individuals with and without medial knee osteoarthritis (OA) during level walking. METHODS: PubMed, Embase, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), Web of Science, and SPORTDiscus were searched from inception to February 2020 by 2 independent reviewers. Included studies compared FPA modification (toe-in or toe-out gait) interventions to lower EKAM and/or KAAI with natural walking. Studies were required to report the first or second peaks of EKAM or KAAI. RESULTS: Sixteen studies were included, and >85% of included patients were graded with Kellgren/Lawrence grade II-IV knee OA. Toe-in gait reduced the first EKAM peak (standardized mean difference [SMD] -0.75 [95% confidence interval (95% CI) -1.05, -0.45]) and KAAI (SMD -0.46 [95% CI -0.86, -0.07]), while toe-out gait reduced the second EKAM peak (SMD -1.04 [95% CI -1.34, -0.75]) in healthy individuals. For patients with knee OA, toe-out gait reduced the second EKAM peak (SMD -0.53 [95% CI -0.75, -0.31]) and KAAI (SMD -0.26 [95% CI -0.49, -0.03]), while toe-in gait did not affect both EKAM peaks and KAAI. CONCLUSION: Discrepancy in biomechanical effects of FPA modification was demonstrated between individuals with and without medial knee OA. Compared with natural walking, both toe-in and toe-out gait may be more effective in lowering EKAM and KAAI in healthy individuals. Toe-out gait may reduce EKAM and KAAI in patients with mild-to-severe knee OA. There is insufficient data from patients with early-stage knee OA, indicating that future research is required.

Difference in the running biomechanics between preschoolers and adults.

BACKGROUND: High vertical loading rate is associated with a variety of running-related musculoskeletal injuries. There is evidence supporting that non-rearfoot footstrike pattern, greater cadence, and shorter stride length may reduce the vertical loading rate. These features appear to be common among preschoolers, who seem to experience lower running injury incidence, leading to a debate whether adults should accordingly modify their running form. OBJECTIVE: This study sought to compare the running biomechanics between preschoolers and adults. METHODS: Ten preschoolers (4.2±1.6 years) and ten adults (35.1±9.5 years) were recruited and ran overground with their usual shoes at a self-selected speed. Vertical average (VALR) and vertical instantaneous loading rate (VILR) were calculated based on the kinetic data. Footstrike pattern and spatiotemporal parameters were collected using a motion capture system. RESULTS: There was no difference in normalized VALR (p=0.48), VILR (p=0.48), running speed (p=0.85), and footstrike pattern (p=0.29) between the two groups. Preschoolers demonstrated greater cadence (p<0.001) and shorter normalized stride length (p=0.01). CONCLUSION: By comparing the kinetic and kinematic parameters between children and adults, our findings do not support the notion that adults should modify their running biomechanics according to the running characteristics in preschoolers for a lower injury risk.

Running biomechanics before and after Pose® method gait retraining in distance runners.

Pose® Method gait retraining has been claimed to modify running form and prevent injury. This study examined the running biomechanics before and after Pose® Method gait retraining. Fourteen runners underwent a 4-week Pose® Method gait retraining program delivered by a certified coach. Paired t-tests were employed to compare vertical average (VALR) and instantaneous loading rates (VILR), lower limb kinematics, footstrike angle and trunk flexion in the sagittal plane before and after the training. Kinetically, there were no significant differences in the VALR (p= 0.693) and VILR (p= 0.782) before and after the training. Kinematically, participants exhibited greater peak hip flexion (p= 0.008) and knee flexion (p= 0.003) during swing. Footstrikeangle also reduced significantly (p= 0.008), indicating a footstrike pattern switch from rearfoot strike to midfoot strike. There was no significant difference in the trunk flexion in the sagittal plane after training (p= 0.658). After a course of Pose® Method gait retraining, runners demonstrated a footstrike pattern switch and some kinematics changes at the hip and knee joint during swing. However, injury-related biomechanical markers (e.g., VALR and VILR) and the trunk kinematics remained similar after training. Runners may consider other gait retraining programs for impact loading reduction.

Evaluation of COVID-19 Restrictions on Distance Runners' Training Habits Using Wearable Trackers.

The COVID-19 pandemic caused widespread disruption to many individuals' lifestyles. Social distancing restrictions implemented during this global pandemic may bring potential impact on physical activity habits of the general population. However, running is one of the most popular forms of physical activity worldwide and one in which it could be maintained even during most COVID-19 restrictions. We aimed to determine the impact of COVID-19 restrictions on runners' training habits through analyzing the training records obtained from their GPS enabled wearable trackers. Retrospective and prospective data were collected from an online database (https://wetrac.ucalgary.ca). Runners' training habits, including frequency, intensity and duration of training, weekly mileage and running locations were analyzed and compared 9 months before and after the start of COVID-19 restrictions in March 2020. We found that runners ran 3 km per week more (p = 0.05, Cohen's d = 0.12) after the start of COVID-19 restrictions, and added 0.3 training sessions per week (p = 0.03, Cohen's d = 0.14). Moreover, runners ran an additional 0.4 sessions outdoors (p < 0.01, Cohen's d = 0.21) but there was no significant change in the intensity or duration of training sessions. Our findings suggested that runners adopted slightly different training regimen as a result of COVID-19 restrictions. Our results described the collective changes, irrespective of differences in response measures adopted by various countries or cities during the COVID-19 pandemic.