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Papers by skylar holmes

Research paper thumbnail of Cartilage Deformation Following A Walking Bout In Individuals With Anterior Cruciate Ligament Reconstruction

Medicine & Science in Sports & Exercise

Research paper thumbnail of Contributing factors to postural stability in Prader-Willi syndrome

Research paper thumbnail of Bone mineral density and its relationship with ground reaction force characteristics during gait in young adults with Prader-Willi Syndrome

Research paper thumbnail of Sex-Specific associations between hip muscle strength and foot progression angle

Journal of Electromyography and Kinesiology

Research paper thumbnail of Influence Of Knee Extensor Strength On Spatiotemporal Gait Parameters In Adults With Prader-willi Syndrome

Medicine and Science in Sports and Exercise, Sep 1, 2022

Research paper thumbnail of Influence of body mass index and anterior cruciate ligament reconstruction on gait biomechanics

Journal of Orthopaedic Research

Body mass index (BMI) and history of anterior cruciate ligament reconstruction (ACLR) independent... more Body mass index (BMI) and history of anterior cruciate ligament reconstruction (ACLR) independently influence gait biomechanics and knee osteoarthritis risk, but the interaction between these factors is unclear. The purpose of this study was to compare gait biomechanics between individuals with and without ACLR, and with and without overweight/obesity. We examined 104 individuals divided into four groups: with and without ACLR, and with low or high BMI (n = 26 per group). Three‐dimensional gait biomechanics were evaluated at preferred speed. The peak vertical ground reaction force, knee flexion angle and excursion, external knee flexion moment, and external knee adduction moment were extracted for analysis. Gait features were compared between groups using 2 (with and without overweight/obesity) × 2 (with and without ACLR) analysis of variance. Primary findings indicated that those with ACLR and high BMI had a larger external knee adduction moment compared with those with low BMI and...

Research paper thumbnail of Body Composition In Adults With Prader-willi Syndrome & Its Relationship With Gait Spatiotemporal Parameters

Medicine & Science in Sports & Exercise

Research paper thumbnail of Lower extremity coordination and joint kinetic distribution during gait in adults with and without Prader-Willi Syndrome

Research paper thumbnail of Knee extensor functional demand in individuals with knee osteoarthritis

Research paper thumbnail of Association between quadriceps function, joint kinetics, and spatiotemporal gait parameters in young adults with and without obesity

Gait & Posture, 2021

BACKGROUND Individuals with obesity have impaired gait and muscle function that may contribute to... more BACKGROUND Individuals with obesity have impaired gait and muscle function that may contribute to reduced mobility and increased fall risk. RESEARCH QUESTIONS (1) what is the difference in spatiotemporal gait parameters and joint kinetics between individuals with and without obesity; (2) what is the association between spatiotemporal gait parameters, joint kinetics, and quadriceps function? METHODS Forty-eight young adults with obesity (BMI = 33.0 ± 4.1 kg/m2) and 48 without obesity (BMI = 21.6 ± 1.7 kg/m2) completed assessments of quadriceps function (peak torque and early/late rate of torque development (RTD)) and walking biomechanics at self-selected speed. Spatiotemporal gait parameters (stance time, double support time, double support to stance ratio, step width, step length, cadence, and gait stability ratio (GSR)) and joint kinetics (total support moment, and relative contribution from extensor moments) were compared using one-way MANOVAs. Partial correlation examined the association between the total support moment and quadriceps function, and spatiotemporal gait parameters controlling for sex and speed. RESULTS Individuals with obesity walked with longer stance (p = 0.01), longer double-limb support (p < 0.001), wider steps (p < 0.001), lower cadence (p = 0.03), and a greater absolute (p < 0.001) but lesser normalized total support moment (p = 0.03) compared with adults without obesity. In those with obesity, greater PT was associated with less double limb support (p = 0.011) and smaller double support to stance ratio (p = 0.006); greater early RTD was associated with less double limb support (r = -0.455, p = 0.0021), less stance time (r = -0.384, p = 0.008), and a smaller double support to stance ratio (r = -0.371, p = 0.011). In those without obesity, a larger total support moment was associated with longer step length (r = 0.512, p < 0.001), lesser cadence (r = -0.497, p < 0.001), and smaller GSR (-0.460, p = 0.001). SIGNIFICANCE Individuals with obesity walk with altered spatiotemporal gait parameters and joint kinetics that may compromise stability. Extended periods of support may be a strategy used by individuals with obesity to increase stability during gait and accomodate insufficient quadriceps function.

Research paper thumbnail of The Relationship Between Gait Mechanics And Constant And Intermittent Pain In Individuals With Knee Osteoarthritis

Medicine & Science in Sports & Exercise, 2021

Research paper thumbnail of Sourcing evidence-based nutrition information

Research paper thumbnail of The influence of body mass index and sex on frontal and sagittal plane knee mechanics during walking in young adults

Gait & Posture, 2021

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Research paper thumbnail of Estimating Ground Reaction Force and Center of Pressure Using Low-Cost Wearable Devices

IEEE Transactions on Biomedical Engineering, 2021

Objective: Ambulatory monitoring of ground reaction force (GRF) and center of pressure (CoP) coul... more Objective: Ambulatory monitoring of ground reaction force (GRF) and center of pressure (CoP) could improve management of health conditions that impair mobility. Insoles instrumented with force-sensitive resistors (FSRs) are an unobtrusive, low-cost, and low-power technology for sampling GRF and CoP in real-world environments. However, FSRs have variable response characteristics that complicate estimation of GRF and CoP. This study introduces a unique data analytic pipeline that enables accurate estimation of GRF and CoP despite relatively inaccurate FSR responses. This paper also investigates whether inclusion of a complementary knee angle sensor improves estimation accuracy. Methods: Seventeen healthy subjects were equipped with an insole instrumented with six FSRs and a string-based knee angle sensor. Subjects walked in a straight line at self-selected slow, preferred, and fast speeds over an in-ground force platform. Twenty repetitions were performed for each speed. Supervised machine learning models estimated weight-normalized GRF and shoe size-normalized CoP, which were re-scaled to obtain GRF and CoP. Results: Anteroposterior GRF, Vertical GRF, and Anteroposterior CoP were estimated with a normalized root mean square error (NRMSE) of less than 5%. Mediolateral GRF and CoP were estimated with an NRMSE of 8.1% and 6.4%, respectively. Knee angle-related features slightly improved GRF estimates.

Research paper thumbnail of Association Between Ankle Kinematics And Knee Kinetics During Landing In Individuals With ACL Reconstruction

Medicine & Science in Sports & Exercise, 2021

Research paper thumbnail of The Functional Movement Screen Is Not Associated With Self-reported Disability, Gait, Or Drop Vertical Jump In Individuals With ACL Reconstruction

Medicine & Science in Sports & Exercise, 2020

METHODS: The endurance-trained group comprised 11 male collegiate cyclists (age, 19.7 ± 0.6 years... more METHODS: The endurance-trained group comprised 11 male collegiate cyclists (age, 19.7 ± 0.6 years; height, 168.4 ± 6.2 cm; weight, 62.7 ± 7.0 kg; body mass index, 22.1 ± 2.4 kg/m), and the untrained group comprised 9 male with no regular endurance training (age, 21.1 ± 1.8 years; height, 170.1 ± 6.6 cm; weight, 72.2 ± 8.1 kg; body mass index, 24.8 ± 1.5 kg/m). Peak oxygen uptake (VO2peak) was initially determined in all participants using incremental exercise test (37.9 ± 4.7 mL/min/kg in the untrained group vs. 60.5 ± 3.6 mL/min/kg in the endurance-trained group). At second visit, the popliteal artery flow-mediated dilation (%FMD) was assessed before and after a 3-h sitting period. During the sitting period, the popliteal artery diameter and blood velocity were measured every hour. RESULTS: The popliteal artery shear rate was significantly and similarly reduced during the sitting period in both groups (the untrained group and the endurance-trained group: 51.9 ± 19.2 sec vs. 58.3 ± 23.5 sec at pre-sit, 25.5 ± 10.9 sec vs. 25.5 ± 15.2 sec at 1h during sitting period, 19.4 ± 7.4 sec -1 vs. 27.5 ± 12.3 sec at 2h during sitting period, 21.4 ± 8.1 sec vs. 20.8 ± 8.3 sec at 3h during sitting period, 29.4 ± 13.9 sec vs. 29.7 ± 15.8 sec at post-sit, P < 0.001). In a 3-h sitting, a significant impairment in popliteal artery %FMD was observed in the untrained group (4.5 ± 0.6 % vs. 1.6 ± 0.2 % P = 0.003), but it was prevented in the endurance-trained group (6.9 ± 0.7 % vs. 6.2 ± 1.3 %, P < 0.431). CONCLUSIONS: In conclusion, the present study revealed that sitting-induced leg endothelial dysfunction is preventable in endurance-trained individuals.

Research paper thumbnail of Dynamic Quadriceps Strength are Associated with Self-Reported Disability Following ACL Reconstruction

Medicine & Science in Sports & Exercise, 2018

Research paper thumbnail of Sagittal Plane Gait Mechanics are Associated with Femoral Cartilage Thickness After ACL Reconstruction

Medicine & Science in Sports & Exercise, 2018

Distance running is a popular recreational activity despite high rates of overuse injury. The eff... more Distance running is a popular recreational activity despite high rates of overuse injury. The efficacy of wearing minimalist shoes to prevent injury has been debated. We previously reported that minimalist runners are more likely to experience site-specific lower extremity pain; however, no clear relationship has been established between shoe type, forefoot (FF) shape (Egyptian, Morton's, or square), and pain. Therefore, the purpose of this study is to examine self-reported pain in the lower limbs in minimalist and traditionally shod runners with various forefoot types. METHODS: Following consent, 48 experienced runners (age: 27.5 ±9.3 yrs, hgt: 172.2 ±10.2 cm, mass: 70.6 ±15.6 kg, gender: 18M/30F) who reported running at least 10 miles a week for the past three months, completed a visual analog scale (VAS) about pain they experience in five common sites of injury: knee, ankle, calf, shin, and foot. A score of ≥3 on the VAS was considered pain. Shoes were categorized as either minimalist (n=40 feet, midsole drop <4mm) or traditional (n=56 feet, midsole drop>4mm). Superior view photographs were taken of the FF and were categorized as Egyptian (EF) (n=73 feet, typical foot with Hallux the most distal toe), Morton's (MF) (n=10 feet, 2 nd toe longer than Hallux), or square (SQ) (n=13 feet, Hallux and 2 nd toe equal length). Separate three-factor chi-square analyses determined if shoe type (minimalist, traditional) and forefoot type (EF, MF, SQ) were related to pain (yes, no). (α=0.05). RESULTS: More minimalist runners with EF reported pain (61.8%; p=0.004) when compared to MF (50%) or SQ (20%). More minimalist runners with EF reported calf pain (77.8%; p=0.028) than those with MF (0%) or SQ (20%). FF type did not relate to pain at any other site. CONCLUSION: Runners with EF are more likely to report pain in at least one location, and specifically in the calf, than runners with other FF shapes when wearing minimalist vs traditional shoes. Minimalist shoes encourage the runner to strike the ground with the forefoot; however, this requires more eccentric loading of the calf musculature and Achilles tendon. Our minimalist runners with EF reported more calf pain than those with other FF types. Other FF types may be better able to absorb the foot contact and muscle forces better than a more typical foot when wearing minimalist shoes.

Research paper thumbnail of Quadriceps Strength and Landing Symmetry Following ACL Reconstruction

Medicine & Science in Sports & Exercise, 2018

Individuals with anterior cruciate ligament reconstruction (ACLR) are at a significant greater ri... more Individuals with anterior cruciate ligament reconstruction (ACLR) are at a significant greater risk of knee osteoarthritis (OA). The heelstrike transient (HST) during gait is indicative of impulsive/high-rate loading, which has been implicated in cartilage degradation and knee OA development. The quadriceps attenuates loading during gait, and quadriceps dysfunction following ACLR may contribute to impulsive loading and knee OA risk. PURPOSE: To determine the differences in quadriceps function between impulsive loaders and non-impulsive loaders during walking gait. METHODS: Forty-five volunteers with unilateral ACLR participated in this study (32F, 20±3 years old, 71±19 kg, 1.7±0.1 m, 23±15 [range 7-58] months post-ACLR). Quadriceps function in the ACLR limb was quantified during maximal isometric contraction at 90° of knee flexion via the peak torque, rate of torque development (RTD) from 20% to 80% of the interval from onset to peak torque, RTD from onset to 100 ms, and RTD from 100ms to 200ms. All values were normalized to body mass. Gait biomechanics were assessed during overground walking at a self-selected pace. A trial was classified as possessing a HST if the ratio of the vertical ground reaction force peak immediately following heelstrike to the impending local minimum exceeded 1.2. Subjects were classified as "Impulsive" loaders if a HST was identified in at least 3 of 5 of trials. Independent t-tests and correlations were utilized for the analysis. RESULTS: 31% of the subjects were identified as Impulsive loaders. However, there were no significant differences between Impulsive and Normal loaders for RTD 20-80% (0.41±0.46 vs. 0.42±0.44, p=0.96), RTD 0-100ms (2.9±1.9 vs. 3.5±2.6, p=0.41), RTD 100-200ms (2.5±1.4 vs. 2.3±1.5, p=0.62), or peak torque (2.2±0.7vs. 2.3±0.7, p=0.45). There were no significant correlations between the %trials with HST and the quadriceps function indices (r=-0.043-0.172, p=0.258-0.952). CONCLUSION: Roughly 1/3 of our subjects were identified as Impulsive loaders. This statistic mirrors the risk of knee OA development (~30%) in the first decade following ACLR. Our data suggest that this relationship is not associated with quadriceps function. Future research is necessary to determine the role of the HST in knee OA development and the factors that contribute to its presence.

Research paper thumbnail of Plantar Flexor Function in Adults with and without Prader–Willi Syndrome

Medicine & Science in Sports & Exercise, 2020

Purpose Prader–Willi Syndrome (PWS) is a form of congenital obesity characterized by excessive bo... more Purpose Prader–Willi Syndrome (PWS) is a form of congenital obesity characterized by excessive body fat, hypotonia, muscle weakness, and physical/cognitive disability. However, the sources of muscle dysfunction and their contribution to mobility are unclear. The purposes of this study were to 1) compare plantar flexor function between adults with and without PWS; and 2) to examine the relationship between plantar flexor function and gait speed in adults with PWS. Methods Participants included 10 adults with PWS, 10 adults without PWS and with obesity, and 10 adults without PWS and without obesity (matched on age and sex). Plantar flexor function was assessed using isokinetic dynamometry (peak torque [PT], early/late rate of torque development [RTD]), Hoffman reflex (H/M ratio), ultrasound imaging (cross-sectional area [CSA], echo intensity, pennation angle, and fascicle length), and peak propulsive force and plantar flexor moment during gait. Outcomes were compared between groups us...

Research paper thumbnail of Cartilage Deformation Following A Walking Bout In Individuals With Anterior Cruciate Ligament Reconstruction

Medicine & Science in Sports & Exercise

Research paper thumbnail of Contributing factors to postural stability in Prader-Willi syndrome

Research paper thumbnail of Bone mineral density and its relationship with ground reaction force characteristics during gait in young adults with Prader-Willi Syndrome

Research paper thumbnail of Sex-Specific associations between hip muscle strength and foot progression angle

Journal of Electromyography and Kinesiology

Research paper thumbnail of Influence Of Knee Extensor Strength On Spatiotemporal Gait Parameters In Adults With Prader-willi Syndrome

Medicine and Science in Sports and Exercise, Sep 1, 2022

Research paper thumbnail of Influence of body mass index and anterior cruciate ligament reconstruction on gait biomechanics

Journal of Orthopaedic Research

Body mass index (BMI) and history of anterior cruciate ligament reconstruction (ACLR) independent... more Body mass index (BMI) and history of anterior cruciate ligament reconstruction (ACLR) independently influence gait biomechanics and knee osteoarthritis risk, but the interaction between these factors is unclear. The purpose of this study was to compare gait biomechanics between individuals with and without ACLR, and with and without overweight/obesity. We examined 104 individuals divided into four groups: with and without ACLR, and with low or high BMI (n = 26 per group). Three‐dimensional gait biomechanics were evaluated at preferred speed. The peak vertical ground reaction force, knee flexion angle and excursion, external knee flexion moment, and external knee adduction moment were extracted for analysis. Gait features were compared between groups using 2 (with and without overweight/obesity) × 2 (with and without ACLR) analysis of variance. Primary findings indicated that those with ACLR and high BMI had a larger external knee adduction moment compared with those with low BMI and...

Research paper thumbnail of Body Composition In Adults With Prader-willi Syndrome & Its Relationship With Gait Spatiotemporal Parameters

Medicine & Science in Sports & Exercise

Research paper thumbnail of Lower extremity coordination and joint kinetic distribution during gait in adults with and without Prader-Willi Syndrome

Research paper thumbnail of Knee extensor functional demand in individuals with knee osteoarthritis

Research paper thumbnail of Association between quadriceps function, joint kinetics, and spatiotemporal gait parameters in young adults with and without obesity

Gait & Posture, 2021

BACKGROUND Individuals with obesity have impaired gait and muscle function that may contribute to... more BACKGROUND Individuals with obesity have impaired gait and muscle function that may contribute to reduced mobility and increased fall risk. RESEARCH QUESTIONS (1) what is the difference in spatiotemporal gait parameters and joint kinetics between individuals with and without obesity; (2) what is the association between spatiotemporal gait parameters, joint kinetics, and quadriceps function? METHODS Forty-eight young adults with obesity (BMI = 33.0 ± 4.1 kg/m2) and 48 without obesity (BMI = 21.6 ± 1.7 kg/m2) completed assessments of quadriceps function (peak torque and early/late rate of torque development (RTD)) and walking biomechanics at self-selected speed. Spatiotemporal gait parameters (stance time, double support time, double support to stance ratio, step width, step length, cadence, and gait stability ratio (GSR)) and joint kinetics (total support moment, and relative contribution from extensor moments) were compared using one-way MANOVAs. Partial correlation examined the association between the total support moment and quadriceps function, and spatiotemporal gait parameters controlling for sex and speed. RESULTS Individuals with obesity walked with longer stance (p = 0.01), longer double-limb support (p < 0.001), wider steps (p < 0.001), lower cadence (p = 0.03), and a greater absolute (p < 0.001) but lesser normalized total support moment (p = 0.03) compared with adults without obesity. In those with obesity, greater PT was associated with less double limb support (p = 0.011) and smaller double support to stance ratio (p = 0.006); greater early RTD was associated with less double limb support (r = -0.455, p = 0.0021), less stance time (r = -0.384, p = 0.008), and a smaller double support to stance ratio (r = -0.371, p = 0.011). In those without obesity, a larger total support moment was associated with longer step length (r = 0.512, p < 0.001), lesser cadence (r = -0.497, p < 0.001), and smaller GSR (-0.460, p = 0.001). SIGNIFICANCE Individuals with obesity walk with altered spatiotemporal gait parameters and joint kinetics that may compromise stability. Extended periods of support may be a strategy used by individuals with obesity to increase stability during gait and accomodate insufficient quadriceps function.

Research paper thumbnail of The Relationship Between Gait Mechanics And Constant And Intermittent Pain In Individuals With Knee Osteoarthritis

Medicine & Science in Sports & Exercise, 2021

Research paper thumbnail of Sourcing evidence-based nutrition information

Research paper thumbnail of The influence of body mass index and sex on frontal and sagittal plane knee mechanics during walking in young adults

Gait & Posture, 2021

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Research paper thumbnail of Estimating Ground Reaction Force and Center of Pressure Using Low-Cost Wearable Devices

IEEE Transactions on Biomedical Engineering, 2021

Objective: Ambulatory monitoring of ground reaction force (GRF) and center of pressure (CoP) coul... more Objective: Ambulatory monitoring of ground reaction force (GRF) and center of pressure (CoP) could improve management of health conditions that impair mobility. Insoles instrumented with force-sensitive resistors (FSRs) are an unobtrusive, low-cost, and low-power technology for sampling GRF and CoP in real-world environments. However, FSRs have variable response characteristics that complicate estimation of GRF and CoP. This study introduces a unique data analytic pipeline that enables accurate estimation of GRF and CoP despite relatively inaccurate FSR responses. This paper also investigates whether inclusion of a complementary knee angle sensor improves estimation accuracy. Methods: Seventeen healthy subjects were equipped with an insole instrumented with six FSRs and a string-based knee angle sensor. Subjects walked in a straight line at self-selected slow, preferred, and fast speeds over an in-ground force platform. Twenty repetitions were performed for each speed. Supervised machine learning models estimated weight-normalized GRF and shoe size-normalized CoP, which were re-scaled to obtain GRF and CoP. Results: Anteroposterior GRF, Vertical GRF, and Anteroposterior CoP were estimated with a normalized root mean square error (NRMSE) of less than 5%. Mediolateral GRF and CoP were estimated with an NRMSE of 8.1% and 6.4%, respectively. Knee angle-related features slightly improved GRF estimates.

Research paper thumbnail of Association Between Ankle Kinematics And Knee Kinetics During Landing In Individuals With ACL Reconstruction

Medicine & Science in Sports & Exercise, 2021

Research paper thumbnail of The Functional Movement Screen Is Not Associated With Self-reported Disability, Gait, Or Drop Vertical Jump In Individuals With ACL Reconstruction

Medicine & Science in Sports & Exercise, 2020

METHODS: The endurance-trained group comprised 11 male collegiate cyclists (age, 19.7 ± 0.6 years... more METHODS: The endurance-trained group comprised 11 male collegiate cyclists (age, 19.7 ± 0.6 years; height, 168.4 ± 6.2 cm; weight, 62.7 ± 7.0 kg; body mass index, 22.1 ± 2.4 kg/m), and the untrained group comprised 9 male with no regular endurance training (age, 21.1 ± 1.8 years; height, 170.1 ± 6.6 cm; weight, 72.2 ± 8.1 kg; body mass index, 24.8 ± 1.5 kg/m). Peak oxygen uptake (VO2peak) was initially determined in all participants using incremental exercise test (37.9 ± 4.7 mL/min/kg in the untrained group vs. 60.5 ± 3.6 mL/min/kg in the endurance-trained group). At second visit, the popliteal artery flow-mediated dilation (%FMD) was assessed before and after a 3-h sitting period. During the sitting period, the popliteal artery diameter and blood velocity were measured every hour. RESULTS: The popliteal artery shear rate was significantly and similarly reduced during the sitting period in both groups (the untrained group and the endurance-trained group: 51.9 ± 19.2 sec vs. 58.3 ± 23.5 sec at pre-sit, 25.5 ± 10.9 sec vs. 25.5 ± 15.2 sec at 1h during sitting period, 19.4 ± 7.4 sec -1 vs. 27.5 ± 12.3 sec at 2h during sitting period, 21.4 ± 8.1 sec vs. 20.8 ± 8.3 sec at 3h during sitting period, 29.4 ± 13.9 sec vs. 29.7 ± 15.8 sec at post-sit, P < 0.001). In a 3-h sitting, a significant impairment in popliteal artery %FMD was observed in the untrained group (4.5 ± 0.6 % vs. 1.6 ± 0.2 % P = 0.003), but it was prevented in the endurance-trained group (6.9 ± 0.7 % vs. 6.2 ± 1.3 %, P < 0.431). CONCLUSIONS: In conclusion, the present study revealed that sitting-induced leg endothelial dysfunction is preventable in endurance-trained individuals.

Research paper thumbnail of Dynamic Quadriceps Strength are Associated with Self-Reported Disability Following ACL Reconstruction

Medicine & Science in Sports & Exercise, 2018

Research paper thumbnail of Sagittal Plane Gait Mechanics are Associated with Femoral Cartilage Thickness After ACL Reconstruction

Medicine & Science in Sports & Exercise, 2018

Distance running is a popular recreational activity despite high rates of overuse injury. The eff... more Distance running is a popular recreational activity despite high rates of overuse injury. The efficacy of wearing minimalist shoes to prevent injury has been debated. We previously reported that minimalist runners are more likely to experience site-specific lower extremity pain; however, no clear relationship has been established between shoe type, forefoot (FF) shape (Egyptian, Morton's, or square), and pain. Therefore, the purpose of this study is to examine self-reported pain in the lower limbs in minimalist and traditionally shod runners with various forefoot types. METHODS: Following consent, 48 experienced runners (age: 27.5 ±9.3 yrs, hgt: 172.2 ±10.2 cm, mass: 70.6 ±15.6 kg, gender: 18M/30F) who reported running at least 10 miles a week for the past three months, completed a visual analog scale (VAS) about pain they experience in five common sites of injury: knee, ankle, calf, shin, and foot. A score of ≥3 on the VAS was considered pain. Shoes were categorized as either minimalist (n=40 feet, midsole drop <4mm) or traditional (n=56 feet, midsole drop>4mm). Superior view photographs were taken of the FF and were categorized as Egyptian (EF) (n=73 feet, typical foot with Hallux the most distal toe), Morton's (MF) (n=10 feet, 2 nd toe longer than Hallux), or square (SQ) (n=13 feet, Hallux and 2 nd toe equal length). Separate three-factor chi-square analyses determined if shoe type (minimalist, traditional) and forefoot type (EF, MF, SQ) were related to pain (yes, no). (α=0.05). RESULTS: More minimalist runners with EF reported pain (61.8%; p=0.004) when compared to MF (50%) or SQ (20%). More minimalist runners with EF reported calf pain (77.8%; p=0.028) than those with MF (0%) or SQ (20%). FF type did not relate to pain at any other site. CONCLUSION: Runners with EF are more likely to report pain in at least one location, and specifically in the calf, than runners with other FF shapes when wearing minimalist vs traditional shoes. Minimalist shoes encourage the runner to strike the ground with the forefoot; however, this requires more eccentric loading of the calf musculature and Achilles tendon. Our minimalist runners with EF reported more calf pain than those with other FF types. Other FF types may be better able to absorb the foot contact and muscle forces better than a more typical foot when wearing minimalist shoes.

Research paper thumbnail of Quadriceps Strength and Landing Symmetry Following ACL Reconstruction

Medicine & Science in Sports & Exercise, 2018

Individuals with anterior cruciate ligament reconstruction (ACLR) are at a significant greater ri... more Individuals with anterior cruciate ligament reconstruction (ACLR) are at a significant greater risk of knee osteoarthritis (OA). The heelstrike transient (HST) during gait is indicative of impulsive/high-rate loading, which has been implicated in cartilage degradation and knee OA development. The quadriceps attenuates loading during gait, and quadriceps dysfunction following ACLR may contribute to impulsive loading and knee OA risk. PURPOSE: To determine the differences in quadriceps function between impulsive loaders and non-impulsive loaders during walking gait. METHODS: Forty-five volunteers with unilateral ACLR participated in this study (32F, 20±3 years old, 71±19 kg, 1.7±0.1 m, 23±15 [range 7-58] months post-ACLR). Quadriceps function in the ACLR limb was quantified during maximal isometric contraction at 90° of knee flexion via the peak torque, rate of torque development (RTD) from 20% to 80% of the interval from onset to peak torque, RTD from onset to 100 ms, and RTD from 100ms to 200ms. All values were normalized to body mass. Gait biomechanics were assessed during overground walking at a self-selected pace. A trial was classified as possessing a HST if the ratio of the vertical ground reaction force peak immediately following heelstrike to the impending local minimum exceeded 1.2. Subjects were classified as "Impulsive" loaders if a HST was identified in at least 3 of 5 of trials. Independent t-tests and correlations were utilized for the analysis. RESULTS: 31% of the subjects were identified as Impulsive loaders. However, there were no significant differences between Impulsive and Normal loaders for RTD 20-80% (0.41±0.46 vs. 0.42±0.44, p=0.96), RTD 0-100ms (2.9±1.9 vs. 3.5±2.6, p=0.41), RTD 100-200ms (2.5±1.4 vs. 2.3±1.5, p=0.62), or peak torque (2.2±0.7vs. 2.3±0.7, p=0.45). There were no significant correlations between the %trials with HST and the quadriceps function indices (r=-0.043-0.172, p=0.258-0.952). CONCLUSION: Roughly 1/3 of our subjects were identified as Impulsive loaders. This statistic mirrors the risk of knee OA development (~30%) in the first decade following ACLR. Our data suggest that this relationship is not associated with quadriceps function. Future research is necessary to determine the role of the HST in knee OA development and the factors that contribute to its presence.

Research paper thumbnail of Plantar Flexor Function in Adults with and without Prader–Willi Syndrome

Medicine & Science in Sports & Exercise, 2020

Purpose Prader–Willi Syndrome (PWS) is a form of congenital obesity characterized by excessive bo... more Purpose Prader–Willi Syndrome (PWS) is a form of congenital obesity characterized by excessive body fat, hypotonia, muscle weakness, and physical/cognitive disability. However, the sources of muscle dysfunction and their contribution to mobility are unclear. The purposes of this study were to 1) compare plantar flexor function between adults with and without PWS; and 2) to examine the relationship between plantar flexor function and gait speed in adults with PWS. Methods Participants included 10 adults with PWS, 10 adults without PWS and with obesity, and 10 adults without PWS and without obesity (matched on age and sex). Plantar flexor function was assessed using isokinetic dynamometry (peak torque [PT], early/late rate of torque development [RTD]), Hoffman reflex (H/M ratio), ultrasound imaging (cross-sectional area [CSA], echo intensity, pennation angle, and fascicle length), and peak propulsive force and plantar flexor moment during gait. Outcomes were compared between groups us...