Cerebellar Transcranial Direct Current Stimulation Applied over Multiple Days Does Not Enhance Motor Learning of a Complex Overhand Throwing Task in Young Adults

Cerebellar transcranial direct current stimulation (tDCS) enhances motor skill and learning in relatively simple motor tasks, but it is unclear if c-tDCS can improve motor performance in complex motor tasks. The purpose of this study was to determine the influence of c-tDCS applied over multiple days on motor learning in a complex overhand throwing task. In a double-blind, randomized, between-subjects, SHAM-controlled, experimental design, 30 young adults were assigned to either a c-tDCS or a SHAM group. Participants completed three identical experiments on consecutive days that involved overhand throwing in a pre-test block, five practice blocks with concurrent c-tDCS, and a post-test block. Overhand throwing endpoint accuracy was quantified as the endpoint error. The first dorsal interosseous muscle motor evoked potential (MEP) amplitude elicited by transcranial magnetic stimulation was used to quantify primary motor cortex (M1) excitability modulations via c-tDCS. Endpoint error significantly decreased over the 3 days of practice, but the magnitude of decrease was not significantly different between the c-tDCS and SHAM group. Similarly, MEP amplitude slightly increased from the pre-tests to the post-tests, but these increases did not differ between groups. These results indicate that multi-day c-tDCS does not improve motor learning in an overhand throwing task or increase M1 excitability.

Automated plantar contact area estimation in a dynamic state using K-Means clustering

BACKGROUND

Estimation of plantar contact area (PCA) can be used for a variety of purposes such as classification of foot types and diagnosis of foot abnormalities. While some techniques have been developed for assessing static PCA, understanding dynamic PCA may improve understanding of gait biomechanics. This study aims (1) to develop an approach to estimate PCA from video images of footprints during walking and (2) to assess the accuracy and generalizability of this method.

METHODS

A sample of 41 ambulatory, young adults (age = 24.3 ± 3.2 years, mass = 67.2 ± 16.9 kg, height = 1.63 ± 0.08 m) completed 10 trials walking on a raised transparent plexiglass platform. Foot contact during walking was recorded using a video camera placed under the platform. An image processing algorithm, Clustering Segmentation, was developed based on identifying color intensity between the PCA and the rest of the foot and plantar contact morphology.

RESULTS

The proposed approach was compared to manual hand tracing, which is widely accepted as the Gold Standard, as well as with an earlier automated approach (Lidstone et al., 2019). Results showed that Clustering Segmentation followed the Gold Standard closely in all phases of gait. The maximum PCA and the maximum PCA length and width generally increased with foot size, indicating that the algorithm could successfully estimate the PCA across a wide range of foot sizes. Results also showed that the proposed approach for obtaining the PCA may be used to characterize various foot types in a dynamic state.

CONCLUSION

Clustering Segmentation algorithm eliminates the need for subjective interpretation of the PCA. The results showed that the algorithm was considerably faster and more accurate than the earlier automated method. The proposed algorithm will be appropriate for assessment of foot abnormalities and provides complementary information to gait analysis.

Prediction of Diabetes Mellitus Progression Using Supervised Machine Learning

Diabetic peripheral neuropathy (DN) is a serious complication of diabetes mellitus (DM) that can lead to foot ulceration and eventual amputation if not treated properly. Therefore, detecting DN early is important. This study presents an approach for diagnosing various stages of the progression of DM in lower extremities using machine learning to classify individuals with prediabetes (PD; n = 19), diabetes without (D; n = 62), and diabetes with peripheral neuropathy (DN; n = 29) based on dynamic pressure distribution collected using pressure-measuring insoles. Dynamic plantar pressure measurements were recorded bilaterally (60 Hz) for several steps during the support phase of walking while participants walked at self-selected speeds over a straight path. Pressure data were grouped and divided into three plantar regions: rearfoot, midfoot, and forefoot. For each region, peak plantar pressure, peak pressure gradient, and pressure-time integral were calculated. A variety of supervised machine learning algorithms were used to assess the performance of models trained using different combinations of pressure and non-pressure features to predict diagnoses. The effects of choosing various subsets of these features on the model's accuracy were also considered. The best performing models produced accuracies between 94-100%, showing the proposed approach can be used to augment current diagnostic methods.

The effect of exercise modality on age-related changes observed during running

INTRODUCTION

With the increase in participation by older adults in endurance events, research is needed to evaluate how exercising throughout the lifespan can affect the aging process regarding gait and mobility. The purpose of this study was to determine how the type of exercise modality one participates in will affect age-related declines observed during running.

METHODS

Fifty-six individuals between the ages of 18-65 who considered running, resistance training or cycling/swimming as their primary form of activity participated in this study. Kinematics were captured using a 10-camera motion capture system while participants ran at a controlled pace of 3.5 m/s (± 5%) over a 10-m runway with force platforms collecting kinetic data. Eight successful trials were chosen for analysis. A one-way ANOVA assessed differences in mean kinematic and kinetic variables of interest between physical activity groups (α = 0.05).

RESULTS

Older resistance trainers exhibited greater maximal knee power compared to older runners. No other group differences were observed.

CONCLUSION

Despite type of exercise modality, regularly participating in exercise has positive effects. This is evident through the preservation of the function of the lower extremity with age, specifically function of the ankle, and its contribution to healthy movement patterns.

The effect of fatigue on running mechanics in older and younger runners

BACKGROUND

The presence of fatigue has been shown to modify running biomechanics. Throughout a run individuals become more fatigued, and the effectiveness of the musculoskeletal protective mechanism can diminish. Older adults are at an elevated risk for sustaining an overuse running related injury. This can be partially explained by changes in the musculoskeletal system and load attenuation.

RESEARCH QUESTION

The purpose was to compare post-fatigue running mechanics between older and younger runners.

METHODS

Thirty runners (15 young, 15 older) between the ages of 18-65 participated in this study. All participants ran at least 15 miles/week. Running kinematics were captured using a 10-camera motion capture system while participants ran over a 10-m runway with force platforms collecting kinetic data under two conditions: C1: rested state at a controlled pace of 3.5 m/s ( ± 5%); C2: post-exertional protocol where pace was not controlled, rather it was monitored based on heartrate and RPE representative of somewhat-hard to hard intensity exercise. Prior to C2, participants underwent an exertional protocol that consisted of a maximal exercise test to induce fatigue and a required cool-down. A 2 (state of fatigue) x 2 (age) MANOVA was run to test for the effects of fatigue and age and their interactions.

RESULTS

No state of fatigue x age interaction was observed. A main effect of age for peak knee extension moment (Y > O; p = 0.01), maximum knee power (Y > O; p = 0.04), maximum hip power (O >Y; p = 0.04), and peak vertical ground reaction force (Y > O; p = 0.007). Regardless of age, participants exhibited decreased knee ROM (p = 0.007) and greater hip extension moment (p < 0.001) in C2 compared to C1.

CONCLUSION

While different in knee and hip mechanics overall, the subtle differences observed demonstrate that older runners exhibit comparable gait adaptions post-fatigue to younger volume-matched runners.

Influence of Cognitive Performance on Musculoskeletal Injury Risk: A Systematic Review

BACKGROUND

While a large number of studies have investigated the anatomic, hormonal, and biomechanical risk factors related to musculoskeletal (MSK) injury risk, there is growing evidence to suggest that cognition is an important injury contributor in the athletic population. A systematic review of the available evidence regarding the influence of cognitive performance on MSK injury risk has yet to be published in the sports medicine literature.

PURPOSE/HYPOTHESIS

The purpose was to determine the effects of cognition on (1) MSK biomechanics during sports-specific tasks and (2) MSK injury occurrence in the athletic population. It was hypothesized that athletes with lower cognitive performance would demonstrate biomechanical patterns suggestive of MSK injury risk and that injured athletes would perform worse on baseline measures of cognition as compared with their noninjured counterparts.

STUDY DESIGN

Systematic review.

METHODS

PubMed and SPORTDiscus were searched from January 2000 to January 2020. Manual searches were performed on the reference lists of the included studies. A search of the literature was performed for studies published in English that reported MSK biomechanics as a function of cognitive performance and MSK injury occurrence after baseline measures of cognition. Two independent reviewers extracted pertinent study data in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2009 guidelines and assessed study quality using the Quality Assessment Tool for Observational Cohort and Cross-sectional Studies from the National Institutes of Health. A meta-analysis was not performed, owing to the heterogeneous nature of the study designs.

RESULTS

Ten studies met inclusion criteria: 4 cognition-MSK biomechanics studies and 6 cognition-MSK injury studies. All 4 cognition-MSK biomechanics studies demonstrated that worse performance on measures of cognition was associated with lower extremity MSK biomechanical patterns suggestive of greater risk for MSK injury. The majority of the cognition-MSK injury studies demonstrated that injured athletes significantly differed on baseline cognition measures versus matched controls or that cognitive performance was a significant predictor for subsequent MSK injury.

CONCLUSION

Although the literature exploring cognitive contributions to MSK injury risk is still in its infancy, it is suggested that sports medicine personnel conduct baseline assessments of cognition-in particular, reaction time and working memory-to identify which athletes may be at elevated risk for future MSK injury.

Use of Pressure-Measuring Insoles to Characterize Gait Parameters in Simulated Reduced-Gravity Conditions

Prior researchers have observed the effect of simulated reduced-gravity exercise. However, the extent to which lower-body positive-pressure treadmill (LBPPT) walking alters kinematic gait characteristics is not well understood. The purpose of the study was to investigate the effect of LBPPT walking on selected gait parameters in simulated reduced-gravity conditions. Twenty-nine college-aged volunteers participated in this cross-sectional study. Participants wore pressure-measuring insoles (Medilogic GmBH, Schönefeld, Germany) and completed three 3.5-min walking trials on the LBPPT (AlterG, Inc., Fremont, CA, USA) at 100% (normal gravity) as well as reduced-gravity conditions of 40% and 20% body weight (BW). The resulting insole data were analyzed to calculate center of pressure (COP) variables: COP path length and width and stance time. The results showed that 100% BW condition was significantly different from both the 40% and 20% BW conditions, p < 0.05. There were no significant differences observed between the 40% and 20% BW conditions for COP path length and width. Conversely, stance time significantly differed between the 40% and 20% BW conditions. The findings of this study may prove beneficial for clinicians as they develop rehabilitation strategies to effectively unload the individual's body weight to perform safe exercises.

Relationship Between Cognitive Performance and Lower Extremity Biomechanics: Implications for Sports-Related Concussion

Background

Collegiate athletes with prior sports-related concussion (SRC) are at increased risk for lower extremity (LE) injuries; however, the biomechanical and cognitive mechanisms underlying the SRC-LE injury relationship are not well understood.

Purpose

To examine the association between cognitive performance and LE land-and-cut biomechanics among collegiate athletes with and without a history of SRC and to determine the association among multiple cognitive testing batteries in the same athlete cohort.

Study Design

Controlled laboratory study.

Methods

A cohort of 20 collegiate athletes with prior SRC (9 men, 11 women; mean ± standard deviation [SD] age, 20.5 ± 1.3 years; mean ± SD time since last SRC, 461 ± 263 days) and 20 matched controls (9 men, 11 women; mean ± SD age, 19.8 ± 1.3 years) completed land-and-cut tasks using the dominant and nondominant limbs. LE biomechanical variables and a functional visuomotor reaction time (FVMRT) were collected during each trial. Athletes also completed the Immediate Post-Concussion Assessment and Cognitive Test (ImPACT) and Senaptec Sensory Station assessments.

Results

In the SRC cohort, Pearson correlation coefficients indicated slower FVMRT was moderately correlated with decreased dominant limb (r = -0.512) and nondominant limb (r = -0.500) knee flexion, while increased dominant limb knee abduction moment was moderately correlated with decreased ImPACT Visual Memory score (r = -0.539) and slower ImPACT Reaction Time (r = 0.515). Most computerized cognitive measures were not associated with FVMRT in either cohort (P > .05).

Conclusion

Decreased reaction time and working memory performance were moderately correlated with decreased sagittal plane knee motion and increased frontal plane knee loading in collegiate athletes with a history of SRC. The present findings suggest a potential unique relationship between cognitive performance and LE neuromuscular control in athletes with a history of SRC injury. Last, we determined that computerized measures of cognitive performance often utilized for SRC management are dissimilar to sport-specific cognitive processes.

Clinical Relevance

Understanding the relationship between cognitive performance and LE biomechanics in athletes with prior SRC may inform future clinical management strategies. Future research should prospectively assess cognitive and biomechanical measures, along with LE injury incidence, to identify mechanisms underlying the SRC-LE injury relationship.

Enhancing the Accuracy of Vertical Ground Reaction Force Measurement During Walking Using Pressure-Measuring Insoles

Pressure-measuring insoles can be an attractive tool for measuring ground reaction force (GRF) since they are portable and can record multiple consecutive steps. Several researchers have, however, observed that these insoles are less accurate than instrumented force platforms. To address this issue, the authors identified transfer functions that best described each insole size to enhance the measurements of the vertical component of GRF during walking. GRF data were collected from 29 participants (6/23 male/female, 24.3 ± 6.7 yrs, 70.4 ± 23.9 kg, 1.66 ± 0.11 m) using Medilogic® pressure-measuring insoles and Kistler® force platforms for three walking trials. Participants provided the institutionally approved written consent (IRB #724468). The data from both instruments were preprocessed. A subset of the data was used to train the system identification toolbox (matlab) to identify the coefficients of several candidate transfer functions for each insole size. The resulting transfer functions were compared using all available data for each insole to assess which one modified the insole data to be closer to that of the force platform. All tested transfer functions moved the vertical component of GRF closer to the corresponding force platform data. Each insole size had a specific transfer model that that yielded the best results. Using system identification techniques produced transfer functions that, when using insole data of the vertical component of GRF as input, produced output that is comparable to the corresponding measurement using an instrumented force platform.

Landing Biomechanics in Adolescent Athletes With and Without a History of Sports-Related Concussion

Recent evidence suggests previously concussed athletes are at greater risk for lower-extremity (LE) injuries than are controls. However, little is known regarding the influence of sports-related concussion (SRC) on landing biomechanics that may provide a mechanistic rationale for LE injury risk. The purpose of this investigation was to examine LE drop-landing biomechanics in adolescent athletes with and without a previous SRC history. Participants included 10 adolescent athletes with an SRC history and 11 controls from multiple sports. Three-dimensional kinematic and kinetic data associated with LE injury risk were analyzed across 5 trials for 30- and 60-cm landing heights. Multivariate analyses indicated group differences in landing patterns from the 30- (P = .041) and 60-cm (P = .015) landing heights. Follow-up analyses indicated that concussed adolescent athletes demonstrated significantly less ankle dorsiflexion and knee flexion versus controls when performing drop landings. Our findings suggest that previously concussed adolescent athletes complete drop-landing maneuvers with ankle and knee joint kinematic patterns that suggest greater risk for LE injury. While limitations such as sport variety and explicit LE injury history are present, the results of this study provide a possible biomechanical rationale for the association between SRC and LE injury risk.

Children with Autism Spectrum Disorder Show Impairments During Dynamic Versus Static Grip-force Tracking

Impairments in visuomotor integration (VMI) may contribute to anomalous development of motor, as well as social-communicative, skills in children with autism spectrum disorder (ASD). However, it is relatively unknown whether VMI impairments are specific to children with ASD versus children with other neurodevelopmental disorders. As such, this study addressed the hypothesis that children with ASD, but not those in other clinical control groups, would show greater deficits in high-VMI dynamic grip-force tracking versus low-VMI static presentation. Seventy-nine children, aged 7-17 years, participated: 22 children with ASD, 17 children with fetal alcohol spectrum disorder (FASD), 18 children with Attention-Deficit Hyperactivity Disorder (ADHD), and 22 typically developing (TD) children. Two grip-force tracking conditions were examined: (1) a low-VMI condition (static visual target) and (2) a high-VMI condition (dynamic visual target). Low-frequency force oscillations <0.5 Hz during the visuomotor task were also examined. Two-way ANCOVAs were used to examine group x VMI and group x frequency effects (α = 0.05). Children with ASD showed a difficulty, above that seen in the ADHD/FASD groups, tracking dynamic, but not static, visual stimuli as compared to TD children. Low-frequency force oscillations <0.25 Hz were also significantly greater in the ASD versus the TD group. This study is the first to report VMI deficits during dynamic versus static grip-force tracking and increased proportion of force oscillations <0.25 Hz during visuomotor tracking in the ASD versus TD group. Dynamic VMI impairments may be a core psychophysiologic feature that could contribute to impaired development of motor and social-communicative skills in ASD. LAY SUMMARY: Children with autism spectrum disorder (ASD) show difficulties using dynamic visual stimuli to guide their own movements compared to their typically developing (TD) peers. It is unknown whether children without a diagnosis of ASD, but with other neurological disorders, show similar difficulties processing dynamic visual stimuli. In this study, we showed that children with ASD show a difficulty using dynamic, but not static, visual stimuli to guide movement that may explain atypical development of motor and social skills.

The Influence of Sport-Related Concussion on Lower Extremity Injury Risk: A Review of Current Return-to-Play Practices and Clinical Implications

Sport-related concussions (SRCs) are now classified as a major health concern affecting athletes across all sporting levels, with recent evidence suggesting upwards of 3.8 million SRCs occur each year. Multiple injury surveillance datasets have recently determined that athletes post-SRC, compared to non-concussed counterparts, are at greater risk for lower extremity (LE) injury beyond the resolution of traditional SRC assessment batteries. However, it is presently uncertain if common clinical practices (symptom reporting, neuropsychological (NP) examination, and static postural control analysis) can determine athletes at risk for LE injury following an SRC. A comprehensive review of the literature determined that these tools may not reveal subtle cognitive and neuromuscular deficits that lead to subsequent LE injury during dynamic sporting tasks. Current return-to-play (RTP) protocols should consider clarifying the addition of specific objective locomotor analysis, such as gait tasks and sport-specific maneuvers, to determine the risk of LE injury after an athlete has sustained an SRC.

A comparison of two techniques for center of pressure measurements

Introduction

Force platforms and pressure-measuring insoles are the most common tools used for measuring center of pressure. Earlier studies to assess these instruments suffered from limited sample sizes or an inadequate range of participant foot sizes. The purpose of this study was to propose new methods to extract and calculate comparably accurate center of pressure for the Kistler® force platform and Medilogic® insoles.

Methods

Center of pressure data were collected from 65 participants wearing pressure-measuring insoles (six different sizes). Participants walked over consecutive force platforms for three trials while wearing pressure-measuring insoles within socks. Onset force thresholds and center of pressure segment length thresholds were used to determine accurate center of pressure path length and width. A single step for each foot and trial was extracted from both instruments.

Results

A strong correlation was observed between instruments in center of pressure length (4.12 ± 6.72% difference, r = 0.74). Center of pressure width varied and was weakly correlated (–7.04 ± 4.48% difference, r = 0.11).

Conclusions

The results indicate that both instruments can measure center of pressure path length consistently and with comparable accuracy (differences < 10%). There were differences between instruments in measuring center of pressure path width, which were attributed to the limited number of sensors across the width of the insoles.

Lesser magnitudes of lower extremity variability during terminal swing characterizes walking patterns in children with autism

BACKGROUND

Anecdotally, children with Autism Spectrum Disorder have highly variable lower extremity walking patterns, yet, this has not been sufficiently quantified. As such, the purpose of this study was to examine walking pattern variability by way of lower extremity coordination and spatio-temporal characteristics in children with autism compared with individuals with typical development during over-ground walking.

METHODS

Bilateral continuous relative phase variability was computed for the thigh-leg, leg-foot, and thigh-foot segment couples for 11 children with autism and 9 children with typical development at each gait sub-phase. Furthermore, left and right stride lengths and stride width were computed and compared. The Model Statistic was utilized to test for statistical differences in variability between each child with autism to an aggregate group with typical development. Effect sizes were computed to determine the meaningfulness between responses for children with autism and typical development. Coefficient of variation and effect sizes were computed for stride lengths and stride width.

FINDINGS

Analysis revealed that children with autism exhibited differences in variability in each gait sub-phase. Notably, all but two children with autism exhibited lesser variability in all segment couples during terminal swing. Differences in stride lengths were relatively minimal, however, greater coefficient of variation magnitudes in stride width were observed in children with autism.

INTERPRETATION

This finding reveals that children with autism may have limited or a preferred movement strategy when preparing the foot for ground contact. The findings from this study suggest variability may be an identifiable characteristic during movement in children with autism.

Footwear and footstrike change loading patterns in running

Loading rates have been linked to running injuries, revealing persistent impact features that change direction among three-dimensional axes in different footwear and footstrike patterns. Extracting peak loads from ground reaction forces, however, can neglect the time-varying loading patterns experienced by the runner in each footfall. Following footwear and footstrike manipulations during laboratory-based overground running, we examined three-dimensional loading rate-time features in each direction (X, Y, Z) using principal component analysis. Twenty participants (9 M, 11 F, age: 25.3 ± 3.6 y) were analysed during 14 running trials in each of two footwear (cushioned and minimalist) and three footstrike conditions (forefoot, midfoot, rearfoot). Two principal components (PC) captured the primary loading rate-time features (PC1: 42.5% and PC2: 22.8% explained variance) and revealed interaction among axes, footwear, and footstrike conditions (PC1: F _{(2.1, 40.1)} = 5.6, p = 0.007, η ² = 0.23; PC2: F _{(2.0, 38.4)} = 62.3, p < 0.001, η ² = 0.77). Rearfoot running in cushioned footwear attenuated impact loads in the vertical direction, and forefoot running in minimalist footwear attenuated impact loads in the anterior-posterior and medial-lateral directions relative to forefoot running in cushioned shoes. Loading patterns depend on footwear and footstrike interactions, which require shoes that match the runner's footstrike pattern.

Concurrent Validity of an Automated Footprint Detection Algorithm to Measure Plantar Contact Area During Walking

BACKGROUND

Monitoring footprints during walking can lead to better identification of foot structure and abnormalities. Current techniques for footprint measurements are either static or dynamic, with low resolution. This work presents an approach to monitor the plantar contact area when walking using high-speed videography.

METHODS

Footprint images were collected by asking the participants to walk across a custom-built acrylic walkway with a high-resolution digital camera placed directly underneath the walkway. This study proposes an automated footprint identification algorithm (Automatic Identification Algorithm) to measure the footprint throughout the stance phase of walking. This algorithm used coloration of the plantar tissue that was in contact with the acrylic walkway to distinguish the plantar contact area from other regions of the foot that were not in contact.

RESULTS

The intraclass correlation coefficient (ICC) demonstrated strong agreement between the proposed automated approach and the gold standard manual method (ICC = 0.939). Strong agreement between the two methods also was found for each phase of stance (ICC > 0.78).

CONCLUSIONS

The proposed automated footprint detection technique identified the plantar contact area during walking with strong agreement with a manual gold standard method. This is the first study to demonstrate the concurrent validity of an automated identification algorithm to measure the plantar contact area during walking.

Computer interactions during walking workstation use moderately affects spatial-temporal gait characteristics

BACKGROUND

Due to increased sedentary workstyles, active workstations have shown the ability to increase activity while only moderately affecting work ability. However, previous examinations have not examine fine motor mousing tasks on tripping descriptors.

RESEARCH QUESTION

What affect do mousing tasks of varying target size have on tripping descriptors during walking workstation use?

METHODS

Three-dimensional kinematic data were collected while participants used a walking workstation completing one baseline and three mousing conditions of varying target sizes.

RESULTS

Target size main effects (p < 0.001) detected decreased stride length in all experimental conditions, which were supported by moderate effect sizes, and decreased stance width and time in double limb support (p < 0.001 for both comparisons). Stance width differences resulted in large effect sizes between baseline and all conditions, while only moderate effect sizes were observed between time in double limb support in baseline compared to all conditions. No changes in knee flexion range of motion were observed in response to target size (p = 0.278).

SIGNIFICANCE

These results indicate that walking workstation users shorten their stride length and decrease their base of support while completing mousing tasks. The placement of the upper extremities on the workstation desk likely acted as the primary mechanism to increase stability. It is concluded that performing mousing tasks of varying target size using a walking workstation does not pose greater risk for adverse gait events.

Electronic measurement of plantar contact area during walking using an adaptive thresholding method for Medilogic® pressure-measuring insoles

BACKGROUND

Pressure-measuring insoles have the potential to measure plantar contact area (PA) during walking. However, they are not widely used for this purpose because of the need for a reliable process that can convert the insole output into PA. The purposes of this study were to: (1) develop an adaptive-threshold method for pressure-measuring insoles that can improve the accuracy of the PA measurements during walking, and (2) experimentally assess the accuracy and generalizability of this method.

METHODS

A sample of 42 healthy, ambulatory, young adults (age=24.3±3.2years, mass=67.2±16.9kg, height=1.63±0.08m) completed 10 trials walking on an elevated walkway while wearing Medilogic^® pressure-measuring insoles (sizes 35-45). A total of six insole sizes were considered. Insole data were converted to PA using three unique adaptive-thresholds that were based on percentages of the maximum sum of digital values (MSDV) during an analyzed step. Three values were considered: 0.1%, 0.2%, and 0.3% of the MSDV. Additionally, a fixed-threshold, which is typically used to estimate PA, was assessed. These two techniques, applied to the insole worn on the left foot, were compared with PA obtained from high-resolution reference footprints obtained from optical pedography of the right foot and processed using digital image processing algorithms. An assumption of PA symmetry between the left (insole) and right (barefoot) feet was made and comparisons were conducted over the entire stance phase of walking. The generalizability of the algorithm was assessed by comparing PA errors from insoles with respect to the optical pedography results based on insole size criteria.

RESULTS

The adaptive-thresholds of 0.1%, 0.2%, and 0.3% of MSDV produced mean errors of 7.31±17.44%, -8.62±15.01%, and -20.45±14.18%, respectively. Using the 2-digital value fixed-threshold produced a mean error of 20.88±22.44%. The best performing adaptive-threshold varied among insole sizes.

CONCLUSION

It was observed that the fixed-threshold technique produced large magnitudes of errors. The proposed adaptive-thresholds of 0.1% and 0.2% of the MSDV reduced PA error to ±10% during walking. The adaptive-threshold method consistently reduced PA error vs. the fixed-threshold for each insole size.

Reviewing the Variability-Overuse Injury Hypothesis: Does Movement Variability Relate to Landing Injuries?

PURPOSE

Overuse injuries are common in sport, but complete understanding of injury risk factors remains incomplete. Although biomechanical studies frequently examine musculoskeletal injury mechanisms, human movement variability studies aim to better understand neuromotor functioning, with proposed connections between overuse injury mechanisms and changes in motor variability.

METHOD

In a narrative review, we discuss the variability-overuse injury hypothesis, which suggests repeated load application leads to mechanical tissue breakdown and subsequent injury when exceeding the rate of physiological adaptation. Due to the multidisciplinary nature of this hypothesis, we incorporate concepts from motor control, neurophysiology, biomechanics, as well as research design and data analysis. We therefore summarize multiple perspectives while proposing theoretical relationships between movement variability and lower extremity overuse injuries.

RESULTS

Experimental data are presented and summarized from published experiments examining interactions between experimental task demands and movement variability in the context of drop landing movements, along with comparisons to previous movement variability studies.

CONCLUSION

We provide a conceptual framework for sports medicine researchers interested in predicting and preventing sports injuries. Under performance conditions with greater task demands, we predict reduced trial-to-trial movement variability that could increase the likelihood of overuse injuries.

Weighted vest effects on impact forces and joint work during vertical jump landings in men and women

Weighted vest (WV) use during vertical jump landings (VJL) does not appear to alter peak vertical ground reaction forces (GRF) or peak joint torques. However, WV effects on joint work and sex differences during VJL are not well understood. This study assessed WV effects on vertical GRF and sagittal joint work during VJL in men and women. Twelve men and 12 women performed VJL wearing a WV with zero added mass (unloaded) and with 10% body mass (loaded) while GRF and kinematic data were obtained. Mixed-model analyses of variance (α = 0.05) and effect sizes (ES) were used to assess differences between sexes and/or load conditions. Regardless of sex, greater landing height (p < 0.001; ES = 0.37) and peak vertical GRF (p = 0.001; ES 0.51) occurred when unloaded, while greater landing time (p = 0.001; ES = 0.46) and negative lower extremity work (p < 0.001; ES = 0.41) occurred when loaded through greater negative work about the hip (p = 0.001; ES = 0.27) and ankle (p = 0.020; ES = 0.27). No differences in hip (p = 0.753; ES = 0.03), knee (p = 0.588; ES = 0.07), or ankle (p = 0.580; ES = 0.09) joint displacement were detected between loaded and unloaded conditions. Men exhibited greater landing heights (p < 0.001; ES = 2.49) and greater peak vertical GRF than women (p = 0.007; ES = 1.18), though women exhibited greater negative lower extremity work (p < 0.001; ES = 1.98) than men through greater negative knee (p < 0.001; ES = 1.98) and ankle (p = 0.032; ES = 0.94) work. No sex differences were detected for joint angular displacement about the hip (p = 0.475; ES = 0.30), knee (p = 0.666; ES = 0.18), or ankle (p = 0.084; ES = 0.71). These data revealed a unique load accommodation strategy during VJL with a WV characterized by greater lower extremity joint work performed via increased joint torque despite lesser landing height and peak vertical GRF. Women appear to perform greater lower extremity joint work than men during VJL despite lesser landing height and peak vertical GRF. Current and prospective WV users should be aware of their load accommodation strategy during VJL with an external load. Women may consider developing more refined load accommodation strategies for VJL regardless of whether external loading is applied to avoid performing excessive amounts of lower extremity work.

Lower extremity joint stiffness during walking distinguishes children with and without autism

How children with Autism Spectrum Disorder (ASD) and peers with typical development (TD) modulate lower extremity stiffness during walking could identify a mechanism for gait differences between groups. We quantified differences in lower extremity joint stiffness and linear impulses, along the vertical and anterior/posterior axes during over-ground walking in children with ASD compared to age- and gender-matched children with TD. Nine age- and gender-matched pairs of children, aged 5-12 years, completed the current study. Joint stiffness and linear impulses were computed in four sub-phases of stance: loading response, mid-stance, terminal stance, and pre-swing. The Model Statistic technique (α = 0.05) was used to test for statistical significance between the matched-pairs for each variable and sub-phase. Furthermore, dependent t-tests (α = 0.05) were utilized, at the group level, to determine whether significant differences existed between sub-phases. Results indicate that children with ASD may exhibit greater stiffness in pre-swing, and thus, produce inefficient propulsive forces during walking. We attribute these differences to sensory processing dysfunction previously observed in children with ASD.

Weighted Walking Influences Lower Extremity Coordination in Children on the Autism Spectrum

There is sparse quantitative research regarding gait coordination patterns of children on the autism spectrum, though previous studies, relying only upon observational data, have alluded to characteristically poor movement coordination. This study compared walking with a weighted vest, a backpack carriage, and an unloaded walking condition on lower extremity coordination among 10 male children (aged 8-17 years) on the autism spectrum. All participants completed 15 gait trials in the following three conditions: (a) unloaded, (b) wearing a backpack weighted with 15% body mass, and (c) wearing a vest weighted with 15% body mass. We used continuous relative phase analysis to quantify lower extremity coordination and analyzed data through both group and single-subject comparisons. We used the Model Statistic to test for statistical significance at each of the normalized data points for each segment couple (thigh-leg, leg-foot, and thigh-foot). The first 10 and last 10 stride blocks were tested for possible accommodation strategies. Group comparisons revealed no coordination changes among the three conditions (likely due to insufficient statistical power), while single-subject comparisons exposed significant decreased variability in gait coordination patterns ( p < .05) in both loaded conditions, relative to the unloaded condition. These participants exhibited variable coordination patterns during the unloaded gait. When walking with loads, coordination pattern variability of the lower extremities was decreased. This finding suggests that walking while carrying or wearing heavy objects may reduce the number of potential motor pattern choices and thus decrease the overall variability of lower extremity movement patterns. Additional research with a larger and more diverse participant sample is required to confirm this conclusion.

Effects of treadmill running velocity on lower extremity coordination variability in healthy runners

With a growing interest in coordination variability and its role in endurance running, it is important to identify the effect of running velocity. The purpose of the current study was to investigate the effect of treadmill running velocity on the coordination and variability of coordination of lower extremity couplings of healthy runners during stance. Fourteen apparently healthy runners ran on a split-belt force instrumented treadmill at five different velocities. Continuous relative phase (CRP) was used to quantify coordination and variability (vCRP) between lower extremity couplings of the right limb (thigh-shank, thigh-foot, shank-foot) during three phases of stance (loading, mid stance, and propulsion). Multiple one-way repeated measure ANOVAs were conducted to identify differences among velocity conditions at each phase and discrete events (initial foot contact, peak knee flexion during stance, and toe-off). Thigh internal/external rotation (IR/ER)-Shank abduction/adduction (AB/AD) coupling was different during the propulsive phase (p = 0.02). Thigh flexion/extension-Shank flexion/extension showed the greatest differences in vCRP across velocity conditions with differences occurring during loading phase, mid stance, propulsive phase, and peak flexion (p < 0.05). Additionally, significant differences were seen in Thigh FL/EX-Shank FL/EX (toe-off, p = 0.01) and Thigh FL/EX-Foot inversion/eversion (IN/EV) (toe-off, p = 0.032). Interestingly, the decreases in vCRP values were accompanied by changes in center of mass vertical motion during stance, but not knee flexion angles. Increases in running velocity led to a more constrained running pattern through a reduction in degrees of freedom.

Performance Differences Among Skilled Soccer Players of Different Playing Positions During Vertical Jumping and Landing

Harry, JR, Barker, LA, James, CR, and Dufek, JS. Performance differences among skilled soccer players of different playing positions during vertical jumping and landing. J Strength Cond Res 32(2): 304-312, 2018-Both jumping and landing performance of skilled soccer players is diminished when task demands are increased. However, it is unclear if performance changes are specific to players of certain playing positions. Therefore, we assessed jumping and landing performance among skilled soccer players of different playing positions. Twenty-five National Collegiate Athletic Association (NCAA) Division 1 male soccer players (179.5 ± 7.8 cm, 75.5 ± 7.1 kg, 19.7 ± 1.2 years) performed maximum effort vertical jump landings (VJLs), whereas vertical ground reaction force (vGRF) data were obtained. Participants were stratified into goalkeeping (GK), defensive (DEF), midfield (MID), and attacking (ATT) group according to their primary playing position. One-way analyses of variance (α = 0.05) and effect sizes (ESs; large ≥ 0.80) were used to compare differences among groups. The jumping phase variables evaluated were jump height, unloading and amortization vGRF magnitudes, eccentric rate of force development, and the reactive strength index. Landing phase variables included the peak vGRF magnitude, vGRF loading rate, vGRF attenuation rate, and landing time. No statistically significant differences were detected for any jumping or landing variable (p ≥ 0.05). However, a number of large magnitude differences were detected during landing after ES calculations. Specifically, greater peak vGRF magnitudes were detected in DEF vs. both MID (ES = 1.08) and ATT (ES = 0.93), a greater vGRF loading rate occurred in DEF vs. MID (ES = 0.93), and a greater vGRF attenuation rate occurred in DEF vs. both MID (ES = 1.00) and AT (ES = 0.80). It is concluded that highly skilled soccer players possess position-specific abilities with respect to the landing phase of VJL. Skilled soccer players might experience enhanced training outcomes after VJL training regimens tailored to the specific demands of their primary playing position.

A Novel Approach to Assessing Head Injury Severity in Pediatric Patient Falls

INTRODUCTION

Pediatric patient falls with head-to-floor impact have the greatest potential for injury.

METHODS

An objective measure of head injury severity, the Head Injury Criterion (HIC₁₅), was calculated from anthropometric and biomechanical components of patient falls. A secondary aim was to compare HIC₁₅ levels with the hospital's subjective assignment of level of harm (1-9 scale) used for regulatory reports.

RESULTS

Adverse event reports yielded a sample of 49 falls from heights of 72.5 to 1793.0 cm by children ages 11 months through 17 years. Contact velocity from beginning to end was 2.81 to 6.16 ms. Mean acceleration was 19.5 to 95.3g. HIC₁₅ levels of impact ranged from 26.4 to 1,330.0, and mean force upon contact was 2.0 to 9.8 N/kg body mass. Seven (14.3%) children's HIC₁₅ levels exceeded age-specific thresholds, with no follow-up scheduled. Hospital-assigned levels of harm were not correlated with HIC₁₅ levels (r = .23, R² = .05, p = .12).

DISCUSSION

A point-of-care computerized HIC₁₅ algorithm would be useful for diagnostic and follow-up decisions.

Examination of gait parameters during perturbed over-ground walking in children with autism spectrum disorder

BACKGROUND

Many children with Autism Spectrum Disorder (ASD) are school-aged and typically carry a backpack. It is important to understand how this task affects walking. Weighted vests (WVs) often prescribed to mitigate behavioral effects of ASD. The effects of backpack and WV walking have not been examined in children with ASD.

AIMS

To quantify differences in lower extremity mechanics in children with ASD during WV and backpack walking.

METHODS

Eight male participants completed 15 trials in three conditions: body mass, and carrying or wearing a backpack or WV with 15% added body mass. Three-dimensional kinematic data were collected and normalized to 100% of the gait cycle. The Model Statistic was utilized to test for bilateral asymmetries between the lower extremity joints at all points along the gait cycle.

RESULTS

Analysis revealed similar numbers of significant asymmetries in hip (71.0, 70.4, 60.6), knee (68.4, 71.5, 74.6), and ankle (64.1, 68.9, 68.4) for unloaded, backpack, and WV, respectively.

CONCLUSION

Participants exhibited individualized kinematic symmetry-responses to the loaded conditions compared to the unloaded condition. These findings suggest that 15% body mass backpack or WV does not affect gait symmetry in children with ASD.

Assessing the validity of pressure-measuring insoles in quantifying gait variables

Introduction

Pressure-measuring insoles can provide a portable alternative to existing gait analysis tools. However, there is disagreement among researchers on their accuracy and the appropriate calibration methods. The purposes of this study were to (1) determine the validity of pressure-measuring insoles for calculating stance time and support-phase impulse during walking using two calibration procedures, and (2) examine the effect of insole size on the results.

Methods

Data were collected from 39 participants (23.5 ± 3.24 yrs, 66.7 ± 17.5 kg, 1.64 ± 0.09 m), each wearing appropriately sized insoles as they walked over two consecutive force platforms. Two calibration methods were evaluated: (1) manufacturer's recommendation, and (2) a participant weight-based approach. Qualitative and quantitative evaluations were conducted.

Results

The results indicated that the insoles measured longer stance times than the force platform (differences are less than 10%). Both calibration methods resulted in inaccurate impulse values (differences are 30 and 50% for the two calibration methods, respectively). The results showed that when using the first calibration method, impulse values depended on insole size. The second calibration consistently underestimated the impulse.

Conclusions

It was concluded that while the insoles provide acceptable qualitative representation of the gait, the two studied calibration methods may lead to a misleading quantitative assessment.

Three-dimensional impact kinetics with foot-strike manipulations during running

BACKGROUND

Lack of an observable vertical impact peak in fore/mid-foot running has been suggested as a means of reducing lower extremity impact forces, although it is unclear if impact characteristics exist in other axes. The purpose of the investigation was to compare three-dimensional (3D) impact kinetics among foot-strike conditions in over-ground running using instantaneous loading rate-time profiles.

METHODS

Impact characteristics were assessed by identifying peak loading rates in each direction (medial-lateral (ML), anterior-posterior (AP), vertical, and 3D resultant) following foot-strike instructions (fore-foot, mid-foot, subtle heel, and obvious heel strike). Kinematic and kinetic data were analyzed among 9 male participants in each foot-strike condition.

RESULTS

Loading rate peaks were observed in each direction and foot-strike condition, differing in magnitude by direction (3D resultant and vertical > AP > ML, p ≤ 0.031) and foot-strike: ML (fore-foot and mid-foot strike > obvious heel strike, p ≤ 0.032), AP (fore-foot and mid-foot strikes > subtle-heel and obvious heel strikes, p ≤ 0.023). In each direction, the first loading rate peak occurred later during heel strike running relative to fore-foot (p ≤ 0.019), with vertical and 3D resultant impact durations exceeding shear (ML and AP, p ≤ 0.007) in each condition.

CONCLUSION

Loading rate-time assessment identified contrasting impact characteristics in each direction and the 3D resultant following foot-strike manipulations, with potential implications for lower extremity structures in running.

Gait Retraining From Rearfoot Strike to Forefoot Strike does not change Running Economy

Gait retraining is a method for management of patellofemoral pain, which is a common ailment among recreational runners. The present study investigated the effects of gait retraining from rearfoot strike to forefoot strike on running economy, heart rate, and respiratory exchange ratio immediately post-retraining and one-month post-retraining in recreational runners with patellofemoral pain. Knee pain was also measured. Sixteen participants (n=16) were randomly placed in the control (n=8) or experimental (n=8) group. A 10-minute treadmill RE test was performed by all subjects. The experimental group performed eight gait retraining running sessions where foot strike pattern was switched from rearfoot strike to forefoot strike, while the control group received no intervention. There were no significant differences for running economy (p=0.26), respiratory exchange ratio (p=0.258), or heart rate (p=0.248) between the groups. Knee pain reported on a visual analog scale was also significantly reduced (p<0.05) as a result of retraining. The present study demonstrates that retraining from rearfoot strike to forefoot strike did not affect running economy up to one-month post-retraining while reducing running-related patellofemoral pain.

Prediction of calcaneal bone competence from biomechanical accommodation variables measured during weighted walking

Carrying weight while walking is a common activity associated with increased musculoskeletal loading, but not all individuals accommodate to the weight in the same way. Different accommodation strategies could lead to different skeletal forces, stimuli for bone adaptation and ultimately bone competence. The purpose of the study was to explore the relationships between calcaneal bone competence and biomechanical accommodation variables measured during weighted walking. Twenty healthy men and women (10 each; age 27.8 ± 6.8 years) walked on a treadmill at 1.34 m/s while carrying 0, 44.5 and 89 N weights with two hands in front of the body. Peak vertical ground reaction force and sagittal plane angular displacements of the trunk and left lower extremity during weight acceptance were measured and used to quantify accommodation. Calcaneal bone stiffness index T-score (BST) was measured using quantitative ultrasound. Correlation and stepwise multiple regression were used to predict calcaneal BST from the accommodation variables. Accommodations of the foot and ankle explained 29 and 54% (p ≤ .015) of the variance in calcaneal BST in different regression models. Statistical resampling using 1000 replications confirmed the strength and consistency of relationships, with the best model explaining 94% of the variance in calcaneal BST. Individuals who change foot and ankle function when carrying heavier weight likely alter the control of gravitational and muscular forces, thereby affecting calcaneal loading, bone adaptation and bone competence. These novel findings illustrate the importance of gait accommodation strategies and highlight a potential clinical consequence that requires further investigation.

Use of active video gaming in children with neuromotor dysfunction: a systematic review

AIM

To examine current evidence on use of active video gaming (AVG) to improve motor function in children with movement disorders including cerebral palsy, developmental coordination disorder, and Down syndrome.

METHOD

Scopus, MEDLINE, Cochrane Library, EMBASE, and CINAHL were searched. Included papers studied the use of AVG for improving movement-related outcomes in these populations. Parameters studied included health condition, strength of evidence, AVG delivery methods, capacity for individualizing play, outcomes addressed, effectiveness for achieving outcomes, and challenges/limitations.

RESULTS

The 20 extracted articles varied in quality. Studies involved children with six different conditions using AVG in clinical, home, or school settings for 49 different motor outcomes. Dosage varied in frequency and duration. Choice of games played and difficulty level were therapist determined (n=6) or child controlled (n=14). The most common study limitations were small sample sizes and difficulty individualizing treatment. All articles showed improvement in outcomes with AVG, although differences were not consistently significant compared with conventional therapy.

INTERPRETATION

Heterogeneity of measurement tools and target outcomes prevented meta-analysis or development of formal recommendations. However, AVG is feasible and shows potential for improving outcomes in this population. Additional investigations of dosing variables, utility as a home supplement to clinical care, and outcomes with larger sample sizes are merited.

Analysis of gait symmetry during over-ground walking in children with autism spectrum disorder

Gait symmetry is utilized as an indicator of neurologic function. Healthy gait often exhibits minimal asymmetries, while pathological gait exhibits exaggerated asymmetries. The purpose of this study was to examine symmetry of mechanical gait parameters during over-ground walking in children with Autism Spectrum Disorder (ASD). Kinematic and kinetic data were obtained from 10 children (aged 5-12 years) with ASD. The Model Statistic procedure (α=0.05) was used to compare gait related parameters between limbs. Analysis revealed children with ASD exhibit significant lower extremity joint position and ground reaction force asymmetries throughout the gait cycle. The observed asymmetries were unique for each subject. These data do not support previous research relative to gait symmetry in children with ASD. Many individuals with ASD do not receive physical therapy interventions, however, precision medicine based interventions emphasizing lower extremity asymmetries may improve gait function and improve performance during activities of daily living.

Lower extremity variability changes with drop-landing height manipulations

Landing is a common lower extremity injury mechanism in sport, with potential connections to movement control accessed through variability measures. We investigated intra-subject lower extremity variability changes following drop-landing height manipulations using standard deviation (SD) and coefficient of variation (CV) among lower extremity peak sagittal joint angles and moments. Fourteen healthy participants completed five drop-landing trials from five heights 20%, 60%, 100%, 140% and 180% maximum vertical jump height (MVJH). Peak joint angles and moments increased with greater landing height (p < 0.001), highlighting inter-joint differences (Flexion: Knee > Hip > Ankle, p < 0.001; Extensor Moment: Hip > Knee > Ankle, in excess of 60% MVJH, p < 0.05). Kinematic and kinetic SD increased with variable magnitudes, while CV decreased at greater landing heights (p ≤ 0.016). Decreased relative variability under greater task demands may underscore non-contact injury mechanisms from repetitive loading of identical structures.

A Comparative Evaluation of Gait between Children with Autism and Typically Developing Matched Controls

Anecdotal reports suggest children with autism spectrum disorder (ASD) ambulate differently than peers with typical development (TD). Little empirical evidence supports these reports. Children with ASD exhibit delayed motor skills, and it is important to determine whether or not motor movement deficits exist during walking. The purpose of the study was to perform a comprehensive lower-extremity gait analysis between children (aged 5-12 years) with ASD and age- and gender-matched-samples with TD. Gait parameters were normalized to 101 data points and the gait cycle was divided into seven sub-phases. The Model Statistic procedure was used to test for statistical significance between matched-pairs throughout the entire gait cycle for each parameter. When collapsed across all participants, children with ASD exhibited large numbers of significant differences (p < 0.05) throughout the gait cycle in hip, knee, and ankle joint positions as well as vertical and anterior/posterior ground reaction forces. Children with ASD exhibited unique differences throughout the gait cycle, which supports current literature on the heterogeneity of the disorder. The present work supports recent findings that motor movement differences may be a core symptom of ASD. Thus, individuals may benefit from therapeutic movement interventions that follow precision medicine guidelines by accounting for individual characteristics, given the unique movement differences observed.

Neuromechanical synergies in single-leg landing reveal changes in movement control

Our purpose was to examine changes in single-leg landing biomechanics and movement control following alterations in mechanical task demands via external load and landing height. We examined lower-extremity kinematic, kinetic, and electromyographic (EMG) adjustments, as well as changes in movement control from neuromechanical synergies using separate principal component analyses (PCA). Nineteen healthy volunteers (15M, 4F, age: 24.3±4.9y, mass: 78.5±14.7kg, height: 1.73±0.08m) were analyzed among 9 single-leg drop landing trials in each of 6 experimental conditions (3 load and 2 landing height) computed as percentages of subject bodyweight (BW, BW+12.5%, BW+25%) and height (H12.5% & H25%). Condition order was counterbalanced, including: 1.) BW·H12.5, 2.) BW+12.5·H12.5, 3.) BW+25·H12.5, 4.) BW·H25, 5.) BW+12.5·H25, 6.) BW+25·H25. Lower-extremity sagittal joint angles and moments (hip, knee, & ankle), vertical ground reaction force (GRFz), and electrical muscle activity (gluteus maximus, biceps femoris, vastus medialis, medial gastrocnemius, & tibialis anterior muscles), were analyzed in each trial. Biomechanical adjustments and neuromechanical synergies were assessed using PCA. Subjects reduced effective landing height through segmental configuration adjustments at ground contact, extending at the hip and ankle joints with greater load and landing height (p⩽0.028 and p⩽0.013, respectively), while using greater medial gastrocnemius pre-activation with greater load (p⩽0.006). Dimension reduction was observed under greater mechanical task demands, compressing and restructuring synergies among patterns of muscle activation, applied loads, and segmental configurations. These results provide insight into movement control and potential injury mechanisms in landing activities.

The effects of gait retraining in runners with patellofemoral pain: A randomized trial

BACKGROUND

Running popularity has increased resulting in a concomitant increase in running-related injuries with patellofemoral pain most commonly reported. The purpose of this study was to determine whether gait retraining by modifying footstrike patterns from rearfoot strike to forefoot strike reduces patellofemoral pain and improves associated biomechanical measures, and whether the modification influences risk of ankle injuries.

METHODS

Sixteen subjects (n=16) were randomly placed in the control (n=8) or experimental (n=8) group. The experimental group performed eight gait retraining running sessions over two weeks where footstrike pattern was switched from rearfoot strike to forefoot strike, while the control group performed running sessions with no intervention. Variables were recorded pre-, post-, and one-month post-running trials.

FINDINGS

Knee pain was significantly reduced post-retraining (P<0.05; effect size=0.294) and one-month follow-up (P<0.05; effect size=0.294). Knee abduction was significantly improved post-retraining (P<0.05; effect size=0.291) and one-month follow-up (P<0.05; effect size=0.291). Ankle flexion was significantly different post-retraining (P<0.05; effect size=0.547), as well as ankle range of motion post-retraining (P<0.05; effect size=0.425) and one-month follow-up (P<0.05; effect size=0.425).

INTERPRETATION

Findings suggest running with a forefoot strike pattern leads to reduced knee pain, and should be considered a possible strategy for management of patellofemoral pain in recreational runners. This trial is registered at the US National Institutes of Health (clinicaltrials.gov) #NCT02567123.