Validation of a commercially available mobile application for velocity-based resistance training.

Background: Velocity-based training (VBT) is commonly used for programming and autoregulation of resistance training. Velocity may also be measured during resistance training to estimate one repetition maximum and monitor fatigue. This study quantifies the validity of Metric VBT, a mobile application that uses camera-vision for measuring barbell range of motion (RoM) and mean velocity during resistance exercises. Methods: Twenty-four participants completed back squat and bench press repetitions across various loads. Five mobile devices were placed at varying angles (0, ±10, and ±20°) perpendicular to the participant. The validity of Metric VBT was assessed in comparison to Vicon motion analysis using precision and recall, Lin's concordance correlation coefficient, and Bland-Altman plots. Proportional bias was assessed using linear regression. Results: Metric VBT accurately detected over 95% of repetitions. It showed moderate to substantial agreement with the Vicon system for measuring RoM in both exercises. The average Limits of Agreement (LoA) for RoM across all camera positions were -5.45 to 4.94 cm for squats and -5.80 to 3.55 cm for bench presses. Metric VBT exhibited poor to moderate agreement with the Vicon system for measuring mean velocity. The average LoA for mean velocity were 0.03 to 0.25 m/s for squats and -5.80 to 3.55 m/s for bench presses. A proportional bias was observed, with bias increasing as repetition velocity increased. Conclusions: Metric VBT's wide LoA for measuring RoM and mean velocity highlights significant accuracy concerns, exceeding acceptable levels for practical use. However, for users prioritizing repetition counts over precise RoM or mean velocity data, the application can still provide useful information for monitoring workout volume.

Effects of running-induced fatigue on joint kinematics and kinetics during overground running: a systematic review and meta-analysis.

This study evaluated the acute fatigue-inducing effect of distance running on kinematics and kinetics during overground running. Standardised mean differences (SMD) with 95% confidence intervals (95% CI) were used to pool data across 16 studies. Effects during consistent (pre- and post-fatigue running speed within ± 5%) versus varied speed running (difference of >5% between running speeds) were analysed separately. There was strong evidence that running-induced fatigue significantly increases ground contact times at consistent running speeds (SMD 0.52 [95% CI 0.22, 0.82]) and moderate evidence that step length shortens at varied running speeds (SMD -1.27 [95% CI -1.79, -0.75]). There was strong evidence that fatigue does not change peak: hip and knee flexion angles, hip adduction angle, hip and knee internal rotation angles, hip and knee extension moments, hip and knee abduction moments, knee abduction angle, knee flexion and extension moments, knee adduction moment, rearfoot eversion angle, and plantarflexion moments, or knee flexion and plantarflexion range of motion during stance. Running-induced fatigue increases contact times and reduces step length, whereas lower-body joint angles and moments are unchanged. Minimising changes in stride parameters could provide a mechanism for reducing the effects of fatigue on running performance.

Gait biomechanics do not differ between adolescents with and without patellofemoral pain.

OBJECTIVES: To determine if adolescents with patellofemoral pain exhibit different biomechanical characteristics to asymptomatic adolescents during walking and running. METHODS: Twenty-eight adolescents with patellofemoral pain (16 male, 12 female, mean [SD] age: 14.3 [1.7] years) and 24 asymptomatic adolescents (13 male, 11 female, mean [SD] age: 14.1 [1.6] years) participated. Participants walked and ran on an instrumented treadmill in a standardized athletic shoe. Continuous hip, knee, and ankle joint angles and moments, and frontal plane pelvic motion were compared between groups using one-dimensional statistical parametric mapping independent t-tests (alpha <0.05). Cadence and stride length were compared between groups using independent t-tests. RESULTS: During walking, adolescents with patellofemoral pain had a higher hip extension moment at 7%-8% of the gait cycle (p = 0.04) and walked with a shorter stride length (mean difference [95% confidence interval] = -0.07 [-0.1, -0.01] m). There were no other differences between groups during walking. During running, adolescents with patellofemoral pain had greater knee flexion than asymptomatic adolescents at 35%-40% of the gait cycle (p = 0.04) and ran with a higher cadence (mean difference [95% confidence interval] = 5.8 [2.0, 9.5] steps/min). There were no other statistically significant differences between groups during running. CONCLUSIONS: Adolescents with patellofemoral pain demonstrate few biomechanical differences to asymptomatic adolescents during walking and running. The identified differences are likely of limited clinical importance. Biomechanical alterations which have been previously associated with patellofemoral pain in adults, may not need to be the target of management of adolescent patellofemoral pain.

The Immediate Biomechanical Effects of a Flat, Flexible School Shoe in Adolescents with Patellofemoral Pain.

INTRODUCTION: Treatment options for adolescent patellofemoral pain (PFP) are limited. School footwear might be a suitable intervention to modulate patellofemoral joint (PFJ) loads in adolescents with PFP. This study examined the immediate effects of a flat, flexible school shoe compared with a traditional school shoe on knee joint kinematics and kinetics, and PFJ reaction force during walking and running in adolescents with PFP. METHODS: A total of 28 adolescents (12 female, 16 male; mean ± SD age, 14.3 ± 1.7 yr) with PFP walked and ran on an instrumented treadmill in two randomly ordered conditions: (i) flat, flexible school shoe and (ii) traditional school shoe. Three-dimensional marker trajectory and ground reaction force data were sampled at 250 and 1000 Hz, respectively. Continuous ankle and knee joint angles and moments, PFJ reaction force, and ankle power were compared between conditions using one-dimensional statistical parametric mapping paired t -tests ( α < 0.05). RESULTS: Walking in the flat, flexible school shoe resulted in a significant reduction in knee flexion (15%-35% of gait cycle, P < 0.001), knee extension moment (15%-40% of gait cycle, P < 0.001), and PFJ reaction force (15%-40% of gait cycle, P < 0.001) compared with the traditional school shoe. During running, knee flexion (10%-33% of gait cycle, P < 0.001), knee extension moment (15%-25% of gait cycle, P < 0.001), and PFJ reaction force (15%-25% of gait cycle, P < 0.001) were lower when wearing the flat, flexible school shoe compared with the traditional school shoe. CONCLUSIONS: PFJ reaction force is reduced when adolescents walk and run in a flat, flexible school shoe compared with a traditional school shoe. Flat, flexible school shoes may be an effective intervention to modulate biomechanical factors related to PFP.

Flat flexible school shoes for adolescents with patellofemoral pain: a randomised, assessor-blinded, parallel-group feasibility trial.

Objectives: To determine the feasibility of conducting a large-scale randomised controlled trial on the efficacy of flat, flexible school footwear versus traditional school footwear in adolescents (aged 12-18 years) with patellofemoral pain (PFP). Methods: Adolescents with PFP were recruited for this study. Participants were randomised to wear either a (1) flat, flexible school shoe or (2) a traditional school shoe. Participants wore the shoes as per school requirements for 12 weeks. Feasibility was assessed by (1) adherence to allocated shoe wear of ≥75% of total weekly school shoe wear time (recorded through weekly log sheets), (2) a recruitment rate of one participant per fortnight and (3) a dropout rate of ≤ 20%. Descriptive statistics were used for feasibility outcomes. Results: 24 adolescents (15 men, 9 women, mean (SD) age 14.3 (1.7) years) participated in this study. Two participants (8%) were lost to follow-up. The recruitment rate was 1.7 participants per fortnight. 11 of 12 participants (91%) in the flat flexible shoe group and 9 of 10 participants (90%) in the traditional shoe group met the minimum adherence for shoe wear. Mean weekly shoe wear was 20 (7.6) and 21 (4.5) hours per week in the flat, flexible, and traditional shoe groups, respectively. Conclusion: Our results indicate that progression to a full-scale randomised controlled trial is feasible based on the current protocol. A full-scale randomised controlled trial powered to detect estimates of treatment efficacy using flat, flexible school shoes versus traditional school shoes is warranted and will guide evidence-based management of adolescent PFP.

Australian secondary school principals', parents', and students' attitudes to prescribed school footwear guidelines.

BACKGROUND: Adolescents are often required to wear footwear that adheres to uniform guidelines at secondary school. There is a paucity of literature on factors influencing school footwear choice and what drives the development of school footwear guidelines. The aims of this study were to describe (i) current school footwear guidelines in secondary schools across Australia, (ii) factors that influence footwear choice in secondary school students and their parents, and (iii) principals, parents, and students' beliefs on factors which contribute to school footwear guidelines. METHODS: An online survey was distributed to principals, secondary school students (aged 14-19 years) and their parents across Australia. The survey included questions on current school footwear guidelines, factors influencing footwear choice (for students and parents), participants beliefs on the effect footwear has on musculoskeletal health, current and previous lower limb pain, and beliefs on factors that contribute to school footwear guidelines. Parent and student responses to factors that influence their footwear choice were compared using proportional odds logistic regression. Students and parents' responses to factors influencing footwear guidelines were compared to principal responses using proportional odds logistic regression. Significance was set at an alpha of < 0.05. RESULTS: Eighty principals, 153 parents and 120 secondary school students responded to the survey. 96% (77/80) of principals reported that their schools have set guidelines for school footwear. 88% of principals considered comfort to be important when developing school footwear guidelines. Proportional odds logistics regression showed that parents and students were 3.4 and 4.9 times more likely, respectively, than principals to rate comfort as being important when schools develop footwear guidelines. More than 40% of students reported experiencing musculoskeletal pain, and 70% of these students reported the pain to be exacerbated when in their school shoes. Less than a third of participants considered healthcare recommendations important to the development of footwear guidelines. CONCLUSIONS: Nearly all principals that participated in this survey had set guidelines for school footwear. There is a discord between parents, students, and principals on the importance that factors such as comfort, play in the development of school footwear guidelines.

The effect of footwear on mechanical behaviour of the human ankle plantar-flexors in forefoot runners.

PURPOSE: To compare the ankle plantar-flexor muscle-tendon mechanical behaviour during barefoot and shod forefoot running. METHODS: Thirteen highly trained forefoot runners performed five overground steady-state running trials (4.5 ± 0.5 m.s-1) while barefoot and shod. Three-dimensional kinematic and ground reaction force data were collected and used as inputs for musculoskeletal modelling. Muscle-tendon behaviour of the ankle plantar-flexors (soleus; medial gastrocnemius; and lateral gastrocnemius) were estimated across the stance phase and compared between barefoot and shod running using a two-way multivariate analysis of variance. RESULTS: During barefoot running peak muscle-tendon unit (MTU) power generation was 16.5% (p = 0.01) higher compared to shod running. Total positive MTU work was 18.5% (p = 0.002) higher during barefoot running compared to shod running. The total sum of tendon elastic strain energy was 8% (p = 0.036) greater during barefoot compared to shod running, however the relative contribution of tendon and muscle fibres to muscle-tendon unit positive work was not different between conditions. CONCLUSION: Barefoot forefoot running demands greater muscle and tendon work than shod forefoot running, but the relative contribution of tendon strain energy to overall muscle-tendon unit work was not greater.

Protocol for a randomised, assessor-blinded, parallel group feasibility trial of flat flexible school shoes for adolescents with patellofemoral pain.

BACKGROUND: There are limited evidence-based treatment options for adolescents with patellofemoral pain (PFP). Flat, flexible footwear have been shown to reduce patellofemoral joint loading and pain in adults with PFP. The efficacy of this intervention in adolescents with PFP is not established. The primary aim of this study is to determine the feasibility of conducting a large-scale randomised controlled trial (RCT) of the effect of flat, flexible school footwear, when compared to traditional school footwear, in adolescents with PFP. The secondary aim is to describe changes in self-reported outcome measures for adolescents with PFP while wearing flat, flexible footwear when compared to traditional school shoes. METHODS: Twenty-four adolescents with PFP will be recruited from the community. Following baseline assessment, participants will be randomly allocated to receive either (i) flat, flexible school footwear or, (ii) traditional school footwear. Participants will wear the shoe as per school requirements throughout a 12-week intervention period. Feasibility will be assessed with (i) ≥ 75% adherence to allocated shoe wear of their total weekly school wear time, (ii) a recruitment rate of one participant per fortnight, and (iii) a dropout rate of ≤ 20%. Patient reported outcome measures will describe changes in knee pain, function, quality of life and global rating of change at 6 and 12 weeks. Descriptive statistics will be used for the primary outcomes of feasibility. DISCUSSION: This study will determine the feasibility of conducting a large scale RCT evaluating the effect of flat, flexible school shoes for adolescents with PFP. A full-scale study will guide evidence-based management of adolescent PFP. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry reference: ACTRN12621001525875 , Date registered: 9th November 2021.

Effect of concurrent strength and endurance training on run performance and biomechanics: A randomized controlled trial.

This parallel-group randomized controlled trial investigated the effect of concurrent strength and endurance (CSE) training on running performance, biomechanics, and muscle activity during overground running. Thirty moderately trained distance runners were randomly assigned to 10-week CSE training (n = 15; 33.1 ± 7.5 years) or a control group (n = 15; 34.2 ± 8.2 years). Participants ran ≥30 km per week and had no experience with strength training. The primary outcome measure was 2-km run time. Secondary outcome measures included lower limb sagittal plane biomechanics and muscle activity during running (3.89 m s-1 and maximal sprinting); maximal aerobic capacity (V̇O2 max); running economy; and body composition. CSE training improved 2-km run time (mean difference (MD): -11.3 s [95% CI -3.7, -19.0]; p = 0.006) and time to exhaustion during the V̇O2 max running test (MD 59.1 s [95% CI 8.58, 109.62]; p = 0.024). The CSE training group also reduced total body fat (MD: -1.05 kg [95% CI -0.21, -1.88]; p = 0.016) while total body mass and lean body mass were unchanged. Hip joint angular velocity during the early swing phase of running at 3.89 m s-1 was the only biomechanical or muscle activity variable that significantly changed following CSE training. CSE training is beneficial for running performance, but changes in running biomechanics and muscle activity may not be contributing factors to the performance improvement. Future research should consider other possible mechanisms and the effect of CSE training on biomechanics and muscle activity during prolonged running under fatigued conditions.

A comparison of plantarflexor musculotendon unit output between plyometric exercises and running.

OBJECTIVES: Plyometric exercises are used to prevent and rehabilitate plantarflexor running injuries. To facilitate exercise programming, this study compared plantarflexor musculotendon output during running to plyometric exercises. DESIGN: Experimental study with cross-over. METHODS: Fourteen trained distance runners performed running, ankle bouncing, A-skips, bounding, and hurdle jumps. Three-dimensional motion capture and force plate data were collected and computational simulations used to calculate gastrocnemius lateralis and soleus musculotendon peak forces, strain, power generation and absorption, and total positive and negative work. Percentage difference and standardised mean differences were used to compare variables between plyometrics and running. Musculotendon units were classified as energy generators or absorbers according to their net mechanical work. RESULTS: Both plantarflexors behaved as net energy generators during running. Plantarflexor peak force and power generation and absorption were lower in the A-skip and ankle bounce compared to running. Soleus behaved as a net energy absorber during hurdle jumps, with greater total negative work (16.5%; standardised mean difference 0.92) and higher peak strain (0.3%; standardised mean difference 0.28) during hurdle jumps than running. Gastrocnemius lateralis behaved as a net energy absorber during bounding, with greater total negative work (63.8%; standardised mean difference 0.81) and peak strain (0.4%; standardised mean difference 0.77) during bounding than running. CONCLUSIONS: The ankle bounce and A-skip may be appropriate exercises when runners desire lower plantarflexor loads than running. Hurdle jumps elicited high soleus loads but low gastrocnemius lateralis loads, highlighting the disparate function of the plantarflexors. Bounding demanded high plantarflexor musculotendon output and may be suitable when eccentric overload is desired.

The relationship between performance and biomechanics in middle-distance runners.

The present study aimed to identify movement patterns most related to running performance among highly trained middle-distance runners. Eleven male runners performed overground running trials on an indoor running track, and three-dimensional analyses techniques were used to measure running kinematics and kinetics. Performance was measured as season and personal best time over 1500 m. The average velocity during the running trials was 7.2 ± 0.3 m/s. The average season and personal best 1500 m race times were 3:49.7 ± 0:05.8 and 3:46.0 ± 0:08.3 minutes, respectively. Regression analysis revealed that a smaller range of sagittal-plane hip motion during swing, less thorax flexion at toe-off and a smaller ankle plantarflexion angle at contact accounted for 95.7% (p < 0.001) of the variation in season best running performance. Less sagittal-plane hip motion during swing and a smaller ankle plantarflexion angle at contact also explained 79% of the variance in personal best time. Slower middle-distance runners make initial ground contact with a more plantarflexed ankle and greater forward lean of the trunk. We recommend that coaches and runners pay attention to ankle, shank and thorax angles during technical development and training to identify opportunities to optimise middle-distance running mechanics and performance.

Effect of Strength Training on Biomechanical and Neuromuscular Variables in Distance Runners: A Systematic Review and Meta-Analysis.

BACKGROUND: Concurrent strength and endurance (CSE) training improves distance running performance more than endurance training alone, but the mechanisms underpinning this phenomenon are unclear. It has been hypothesised that biomechanical or neuromuscular adaptations are responsible for improvements in running performance; however, evidence on this topic has not been synthesised in a review. OBJECTIVE: To evaluate the effect of CSE training on biomechanical and neuromuscular variables in distance runners. METHODS: Seven electronic databases were searched from inception to November 2018 using key terms related to running and strength training. Studies were included if the following criteria were met: (1) population: 'distance' or 'endurance' runners of any training status; (2) intervention: CSE training; (3) comparator: running-only control group; (4) outcomes: at least one biomechanical or neuromuscular variable; and, (5) study design: randomised and non-randomised comparative training studies. Biomechanical and neuromuscular variables of interest included: (1) kinematic, kinetic or electromyography outcome measures captured during running; (2) lower body muscle force, strength or power outcome measures; and (3) lower body muscle-tendon stiffness outcome measures. Methodological quality and risk of bias for each study were assessed using the PEDro scale. The level of evidence for each variable was categorised according to the quantity and PEDro rating of the included studies. Between-group standardised mean differences (SMD) with 95% confidence intervals (95% CI) were calculated for studies and meta-analyses were performed to identify the pooled effect of CSE training on biomechanical and neuromuscular variables. RESULTS: The search resulted in 1578 potentially relevant articles, of which 25 met the inclusion criteria and were included. There was strong evidence that CSE training significantly increased knee flexion (SMD 0.89 [95% CI 0.48, 1.30], p < 0.001), ankle plantarflexion (SMD 0.74 [95% CI 0.21-1.26], p = 0.006) and squat (SMD 0.63 [95% CI 0.13, 1.12], p = 0.010) strength, but not jump height, more than endurance training alone. Moderate evidence also showed that CSE training significantly increased knee extension strength (SMD 0.69 [95% CI 0.29, 1.09], p < 0.001) more than endurance training alone. There was very limited evidence reporting changes in stride parameters and no studies examined changes in biomechanical and neuromuscular variables during running. CONCLUSIONS: Concurrent strength and endurance training improves the force-generating capacity of the ankle plantarflexors, quadriceps, hamstrings and gluteal muscles. These muscles support and propel the centre of mass and accelerate the leg during running, but there is no evidence to suggest these adaptations transfer from strength exercises to running. There is a need for research that investigates changes in biomechanical and neuromuscular variables during running to elucidate the effect of CSE training on run performance in distance runners.