Skylar Holmes

All Publications

• Patterns of Muscle Health in Single- and Multi-Site Chronic Pain: A UK Biobank Normative Modeling Study. medRxiv : the preprint server for health sciences Kaptan, M., Wang, Y., de Boer, A., Goyal, A., Holmes, S., Ozkan, K., Bédard, S., Indriolo, T., Law, C. S., Pfyffer, D., Fundaun, J., Berhe, E., Gold, G. E., Chaudhari, A., Anoosha, P. S., Gatti, A. A., Kogan, F., Hargreaves, B. A., Delp, S. L., Ratliff, J., Hu, S., Veeravagu, A., Desai, A., Tharin, S., Alamin, T., Smith, A. C., McKay, M. J., Kim, B., Walsh, R., Schielke, A., Dennis, D., Decker, J., De Leener, B., Cohen-Adad, J., Smith, Z. A., Muhammad, F., Elliott, J. M., Marquand, A. F., Mackey, S., Wesselink, E. O., Weber, K. A. 2026

  Abstract

  Chronic pain is associated with impaired muscle health, but whether these changes reflect site-specific factors, broader systemic factors, or both remains unclear. The purpose of this study is to determine whether normative markers of muscle health derived from MRI show site-specific patterns in chronic pain.UK Biobank participants who underwent whole-body MRI from 2006 to 2010 were included in this retrospective cross-sectional study. The MuscleMap Toolbox quantified volume and intramuscular fat (IMF) in 42 muscles of the abdomen, pelvis, and thigh. Normative models trained on a no pain group generated muscle-specific deviations from normal (i.e., Z-scores) for single- and multi-site chronic and acute pain.Of 17,843 participants, the primary site-specific analysis included 9,704 no pain, 885 single-site chronic back pain (CBP), 438 single-site chronic hip pain (CHP), and 1,315 single-site chronic knee pain (CKP) participants (n=12,342; mean age 63.7±7.5 years; 52.7% female). Additional analyses included single-site chronic neck/shoulder pain, acute pain, and multi-site chronic pain groups. In CBP, deviations were localized to abdominal muscles, with decreased volume in 6/8 and increased IMF in 6/8. In CHP, deviations were broad, with decreased volume in 3/8 of the abdominal and 14/26 of the thigh muscles, and increased IMF in 6/8 of the abdominal, 5/8 of the pelvic, and 4/26 of the thigh muscles. In CKP, deviations were localized to thigh muscles, with decreased volume in 8/26 and increased IMF in 6/26. Acute pain groups showed no significant differences except for decreased volume in one thigh muscle in acute knee pain. With each additional chronic pain site, volume decreased (β=-.078;IQR:-0.100-0.051), and IMF increased (β=.085;IQR:0.066-0.101). Combined Z-scores classified chronic pain groups better than chance (accuracy: 48.6%;p<.001), but not acute pain groups (accuracy: 39.0%;p=.20).Whole-body MRI combined with AI-driven muscle segmentation and normative modeling revealed site-specific patterns of muscle health in single-site chronic pain.

  View details for DOI 10.64898/2026.06.19.26356062

  View details for PubMedID 42396320

  View details for PubMedCentralID PMC13321162

• Knee extensor muscles of active older adults with knee osteoarthritis are smaller and weaker but not more fatigable than healthy older adults: Relevance to physical function. Osteoarthritis and cartilage open Holmes, S. C., Kent, J. A., Martini, D. N., Bigelow, C., Boyer, K. A. 2026; 8 (2): 100802

  Abstract

  While knee extensor (KE) muscle weakness (lower peak torque or power) is common with knee osteoarthritis (KOA), less is known about muscle fatigue (acute decrement in peak torque or power in response to contractile activity) and its impact on mobility in KOA. The aim of this study was to quantify KE muscle weakness, fatigue and mobility in response to a 30-min treadmill walk (30 MTW) in older adults with and without KOA.Eighteen KOA (73±3 yr) and 18 healthy (71±3 yr,) participants completed a standardized 30 MTW to induce KE muscle fatigue and changes in mobility (Short Physical Performance Battery scores, SPPB). Peak torque and power (120°/s and 240°/s) were quantified pre- and post-30 MTW. Muscle size (maximal fatfree cross-sectional area; mCSA, cm2) and fat fraction were quantified using MRI, and specific power was calculated as peak muscle power/mCSA (Nm×cm-2). Habitual physical activity was quantified using accelerometry.Lower KE peak and specific torque and power, SPPB and gait speed in KOA at baseline indicated weaker, smaller, fattier muscles, and compromised mobility compared with healthy adults. Muscle fatigue post-30 MTW was significant but did not differ by group. SPPB scores did not change post-30 MTW in either group.Older adults with and without KOA experienced KE muscle fatigue in response to a 30 MTW. While KOA were weaker and had lower physical function at baseline, muscle fatigue did not exacerbate these deficits, suggesting that interventions for mobility in individuals with KOA should continue to target muscle atrophy and weakness rather than fatigue.

  View details for DOI 10.1016/j.ocarto.2026.100802

  View details for PubMedID 42100142

  View details for PubMedCentralID PMC13145384

• REVEALING SYSTEMIC MUSCLE ADAPTATIONS IN KNEE OSTEOARTHRITIS USING NORMATIVE MODELING OF THE UK BIOBANK Holmes, S. C., Wesselink, E. O., Mackey, S., Kogan, F., Gold, G., Weber, K. A., Kaptan, M. ELSEVIER SCI LTD. 2026: S261-S262

  View details for Web of Science ID 001762967700003

• MOVEMENT EVOKED PAIN EXACERBATES FATIGABILITY IN KNEE OSTEOARTHRITIS Boyer, K. A., Holmes, S. C. ELSEVIER SCI LTD. 2026: S165-S166

  View details for Web of Science ID 001761888300031

• Sex-Specific Associations Between Body Mass Index and Knee Flexion Kinematics and Kinetics in Individuals With Anterior Cruciate Ligament Reconstruction JOURNAL OF SPORT REHABILITATION Smith, M. D., Holmes, S. C., Heredia, C. E., Shumski, E. J., Pamukoff, D. N. 2025: 512-520

  Abstract

  Pedometers are a useful measure of physical activity (PA) but whether systematic bias exists when using differing inclusion criterion for pedometer-derived PA data is unknown. We undertake an exploration of previously published criteria for pedometer data cleaning and examine the impact of different inclusion criteria on sample size retention and participant exclusion by key sociodemographic characteristics.Data were drawn from a community survey in Aotearoa/New Zealand. Sociodemographic information and self-reported PA were collected via face-to-face surveys; participants were asked to wear a Yamax CW300 pedometer for 7 days. Analyses involved removing extreme outliers and determining minimum steps per day for inclusion, determining whether day 1 removal was required, examining risk of bias using different inclusion criteria, and examining convergent and concurrent validity of criteria with the lowest bias potential.Pedometer data were available for 895 participants. A threshold of 100 steps/day was deemed appropriate to define a valid day. All days were correlated with each other; intraclass correlation coefficients were low and did not change meaningfully with removal of the first day of data. Participant retention reduced, and bias in participant inclusion increased, with increasing stringency of data inclusion criterion applied. Evidence for convergent and concurrent validity in the 2 models with the lowest risk of exclusion bias was demonstrated.Increasing stringency in pedometer data inclusion criteria can result in significant and biased loss of sample size. Clear reporting of data cleaning methods and rationale (including consideration of potential for bias) is needed in pedometer-based PA research.

  View details for DOI 10.1123/jsr.2024-0167

  View details for Web of Science ID 001484648200001

  View details for PubMedID 39914378

• KNEE EXTENSOR MUSCLE FATIGUE ALTERS GAIT MECHANICS AND ACTIVATION PATTERNS IN OLDER ADULTS WITH KNEE OSTEOARTHRITIS Holmes, S. C., Kent, J. A., Martini, D. N., Bigelow, C., Boyer, K. ELSEVIER SCI LTD. 2025

  View details for Web of Science ID 001529022600075

• Lower extremity joint angle, moment, and coordination throughout a double limb drop vertical jump in individuals with anterior cruciate ligament reconstruction SPORTS BIOMECHANICS Dennis, J. D., Holmes, S. C., Heredia, C., Shumski, E. J., Pamukoff, D. N. 2025; 24 (6): 1753-1768

  Abstract

  Individuals with anterior cruciate ligament reconstruction (ACLR) utilise different landing biomechanics between limbs, but previous analyses have not considered the continuous or simultaneous joint motion that occurs during landing and propulsion. The purpose of this study was to compare sagittal plane ankle/knee and knee/hip coordination patterns as well as ankle, knee, and hip angles and moments and vertical ground reaction force (vGRF) between the ACLR and uninjured limbs during landing and propulsion. Fifteen females and thirteen males performed a drop vertical jump from a 30 cm box placed half their height from force platforms. Coordination was compared using a modified vector coding technique and binning analysis. Kinematics and kinetics were time normalised for waveform analyses. Coordination was not different between limbs. The ACLR limb had smaller dorsiflexion angles from 11 to 16% of landing and 24 to 75% of landing and propulsion, knee flexion moments from 5 to 15% of landing, 20 to 31% of landing, and 35 to 91% of landing and propulsion, and vGRF from 92 to 94% of propulsion compared with the uninjured limb. The ACLR limb exhibited smaller dorsiflexion angles to potentially reduce the knee joint moment arm and mitigate the eccentric and concentric demands on the ACLR knee during landing and propulsion, respectively.

  View details for DOI 10.1080/14763141.2024.2356845

  View details for Web of Science ID 001227891800001

  View details for PubMedID 38767326

• The Influence of Knee Position on Ultrasound Imaging of Femoral Cartilage in Individuals with Anterior Cruciate Ligament Reconstruction CARTILAGE Battersby, H. S., Holmes, S. C., Shumski, E. J., Heredia, C. E., Garcia, S. A., Pamukoff, D. N. 2024; 15 (2): 84-93

  Abstract

  Articular cartilage is important for knee function and can be imaged using ultrasound. The purpose was to compare femoral cartilage thickness and echo intensity (EI) measured at 90° and 140° of knee flexion and between limbs in a cohort with unilateral anterior cruciate ligament reconstruction (ACLR). We also examined associations between gait biomechanics and cartilage outcomes.Twenty-seven individuals with primary unilateral ACLR participated (12 men, 15 women; age = 22.3 ± 3.8 years; time since ACLR = 71.2 ± 47.2 months). Ultrasound was used to obtain femoral cartilage measurements. Gait outcomes included peak KFA (knee flexion angle) and peak external knee flexion moment (KFM). Cartilage outcomes were compared using a 2 (position) × 2 (limb) repeated measures ANOVA (analysis of variance). Gait and cartilage associations were assessed using linear regression.There were no position × limb interactions for any cartilage outcome (all P > 0.05). Medial (P = 0.038) and central cartilage (P < 0.001) were thicker, whereas central (P = 0.029) and lateral cartilage EI (P = 0.003) were lower when measured at 90° than those at 140° of knee flexion. Medial cartilage was thicker in the ACLR than that in the contralateral limb (P = 0.016). A larger KFM was associated with thicker medial cartilage (ΔR2 = 0.146, P = 0.021) and central cartilage (ΔR2 = 0.159, P = 0.039) measured at 140° of knee flexion in the ACLR limb but not at 90°.Findings suggest that imaging position influences cartilage thickness and EI measurements in individuals with ACLR and should be considered in study designs and clinical evaluation. A greater KFM was associated with thicker cartilage within specific portions of the distal femur.

  View details for DOI 10.1177/19476035231205682

  View details for Web of Science ID 001087249100001

  View details for PubMedID 37846037

  View details for PubMedCentralID PMC11368891

• Cartilage deformation following a walking bout in individuals with anterior cruciate ligament reconstruction JOURNAL OF ORTHOPAEDIC RESEARCH Pamukoff, D. N., Holmes, S. C., Heredia, C. E., Shumski, E. J., Garcia, S. A., Montgomery, M. M. 2024; 42 (2): 349-359

  Abstract

  The purpose was to (1) compare the effect of a walking bout on femoral cartilage deformation between limbs with and without anterior cruciate ligament reconstruction (ACLR) and (2) examine the association between gait kinetics and the magnitude of cartilage deformation. A total of 30 individuals with primary unilateral ACLR completed this study [14 male, 16 female; age = 22.57 (3.78) years; body mass index (BMI) = 25.88 (5.68) kg/m2 ; time since ACLR = 61.00 (16.43) months]. Overground walking biomechanics were assessed on day 1, and a 30-min walking bout or 30-min resting bout (control) were completed on days 2 and 3 (counterbalanced order). Femoral cartilage thickness was measured using ultrasound before, immediately following, and 30-min following each intervention. Linear mixed effects models compared the effect of walking on cartilage thickness between the ACLR and contralateral limbs after adjusting for sex, BMI, speed, and the number of steps. Stepwise regression examined the association between the external knee flexion and adduction moments and cartilage deformation following walking. There was a significant limb × time interaction for medial cartilage thickness. Post hoc analyses indicated that cartilage thickness decreased immediately following walking in the contralateral but not ACLR limb. Main effects of limb were observed for medial, central, and lateral cartilage thickness indicating thicker cartilage in the ACLR compared with contralateral limb. A higher knee adduction moment was associated with greater cartilage deformation in the ACLR limb. Femoral cartilage in the ACLR limb exhibited a less dynamic response to walking than the uninvolved limb, which may be due to habitual underloading during gait.

  View details for DOI 10.1002/jor.25694

  View details for Web of Science ID 001077346900001

  View details for PubMedID 37772457

• Contributing factors to postural stability in Prader-Willi syndrome HUMAN MOVEMENT SCIENCE Rubin, D. A., Rose, D. J., Escano, D. L., Holmes, S. C., Garcia, S. A., Pamukoff, D. N. 2023; 91: 103125

  Abstract

  Prader-Willi Syndrome (PWS) is a rare neurodevelopmental disorder affecting multiple functional parameters. This study examined postural stability and associated gait and neuromuscular factors in young adults with PWS.Participants included 10 adults with PWS [7 M/3F; Body Fat % 40.61 ± 7.79]; ten normal weight (NW) adults [7 M/3F; Body Fat % 23.42 ± 7.0]; ten obese (OB) adults [7 M/3F; Body Fat % 42.40 ± 5.62]. Participants completed the Sensory Organization Test (SOT)®. Condition (C) specific and a composite equilibrium score (CES) were calculated (maximum = 100). Quadriceps strength was assessed using an isokinetic dynamometer. Three-dimensional gait analyses were completed along a 10 m walkway using a motion capture system and two force plates. A gait stability ratio (GSR) was computed from gait speed and step length (steps/m).The PWS group had lower scores for C1, C3, C4 and CES compared to the NW (p < .039 for all) and lower scores for C4 and CES than the OB (p < .019 for both) groups, respectively. In C5 (eyes closed, sway-referenced support) and C6 (sway-referenced vision and support), 33.3% of participants with PWS fell during the first trial in both conditions (X2 [2] 7.436, p = .024) and (X2 [2] 7.436, p = .024) but no participant in the other groups fell. Those with PWS showed higher GSR than participants with NW (p = .005) and those with obesity (p = .045).Individuals with PWS had more difficulty maintaining standing balance when relying on information from the somatosensory (C3), visual-vestibular (C4) and vestibular systems (C5, C6). A more stable walk was related to shorter steps, slower velocity and reduced peak quadriceps torque. Participation in multisensory activities that require appropriate prioritization of sensory system(s) input for controlling balance in altered sensory environments should be routinely included. In addition, exercises targeting muscular force and power should be included as part of exercise programming in PWS.

  View details for DOI 10.1016/j.humov.2023.103125

  View details for Web of Science ID 001050346000001

  View details for PubMedID 37515958

• Bone mineral density and its relationship with ground reaction force characteristics during gait in young adults with Prader-Willi Syndrome BONE REPORTS Rubin, D. A., Holmes, S. C., Ramirez, J., Garcia, S. A., Shumski, E. J., Pamukoff, D. N. 2023; 19: 101700

  Abstract

  The incidence of osteopenia and osteoporosis is of concern in adults with Prader-Willi syndrome (PWS). Walking generates reaction forces that could stimulate bone mineralization and is popular in people with PWS. This study compared bone parameters and ground reaction forces (GRF) during gait between young adults with PWS and without PWS and explored associations between bone and GRFs during gait.10 adults with PWS, 10 controls with obesity (OB) and 10 with normal weight (NW) matched on sex participated. Segmental and full body dual-energy x-ray absorptiometry scans provided femoral neck, spine, total body minus the head bone mineral density (BMD), bone mineral content (BMC). Vertical GRF, vertical impulse, posterior force and negative impulse were measured during 5 walking trials at a self-selected speed along a 10 m runway.Multivariate analyses of variance showed that adults with PWS (n = 7-8) had hip and body BMD and BMC comparable (p > .050) to NW and lower (p < .050) than OB. Adults with PWS showed slower speed than NW (p < .050) but similar to OB (p > .050). Adults with PWS presented lower absolute vertical GRF, vertical impulse and negative impulse than OB (p < .050). Pearson r correlations (p < .050) in those with PWS (n = 7-8) indicated that femoral neck BMC was associated with vertical GRF (r = 0.716), vertical impulse (r = 0.780), posterior force (r = -0.805), and negative impulse (r = -0.748). Spine BMC was associated with speed (r = 0.829) and body BMD was associated with speed (r = 0.893), and posterior force (r = -0.780).Increased BMC in the femoral neck and body were associated with larger breaking forces during walking, a phenomenon normally observed at greater gait speeds. Faster walking speed was associated with greater BMC in the spine and body. Our preliminary results suggest that young adults with PWS could potentially benefit from faster walking for bone health; however, larger prospective studies are needed to confirm this.

  View details for DOI 10.1016/j.bonr.2023.101700

  View details for Web of Science ID 001046965200001

  View details for PubMedID 37520935

  View details for PubMedCentralID PMC10382280

• Sex-Specific associations between hip muscle strength and foot progression angle. Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology Holmes, S. C., Montgomery, M. M., Lynn, S. K., Pamukoff, D. N. 2023; 68: 102723

  Abstract

  The foot progression angle (FPA) influences knee loading during gait, but its determinants are unclear. The purpose of this study was to compare FPA between males and females and also examine the association between lower extremity kinematics during gait, hip strength, and the FPA. 25 males and 25 females completed 5 gait trials while FPA and frontal and transverse plane hip and knee angles were calculated from the dominant limb during the foot flat portion of stance. Hip extensor/flexor, abductor/adductor, and internal/external rotator strength were evaluated using maximum voluntary isometric contractions. One-way MANOVAs compared gait and strength outcomes. Stepwise regression assessed the association between FPA, and MVIC and kinematics after accounting for speed in males and females. There was no difference in FPA between sexes (p > 0.05), but females had greater frontal and transverse plane hip angles compared with males (all p < 0.05). Greater hip abduction (p = 0.02) strength was associated with greater FPA, but only in males. In males, greater hip abductor strength may contribute to a more neutral position of the foot during gait, which could help maintain an equal knee loading distribution. Our results suggest that there are sex specific control strategies to achieve a similar FPA during gait.

  View details for DOI 10.1016/j.jelekin.2022.102723

  View details for PubMedID 36402073

• A Wearable System to Monitor Gait Modification Liu, Y., Holmes, S., Boyer, K., Lee, S., IEEE IEEE. 2023

  View details for DOI 10.1109/BSN58485.2023.10331011

  View details for Web of Science ID 001116732100017

• Influence of body mass index and anterior cruciate ligament reconstruction on gait biomechanics JOURNAL OF ORTHOPAEDIC RESEARCH Pamukoff, D. N., Holmes, S. C., Garcia, S. A., Vakula, M. N., Shumski, E. J., Moffit, T. J. 2023; 41 (5): 994-1003

  Abstract

  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 with (p = 0.004) and without ACLR (p = 0.005), and compared with those without ACLR and high BMI (p = 0.001). The main effects of ACLR and BMI group were found for the knee flexion moment, and those with ACLR and with high BMI had lower knee flexion moments compared with those without ACLR (p = 0.031) and with low BMI (p = 0.021), respectively. Data suggest that individuals with ACLR and high BMI may benefit from additional intervention targeting the knee adduction moment. Moreover, lower external knee flexion moments in those with high BMI and ACLR were consistent, but high BMI did not exacerbate deficits in the knee flexion moment in those with ACLR. [Correction added on 9 November 2022, after first online publication: In the preceding sentence, for clarity, the words "reductions in the lower" was removed from the initial sentence to read "Moreover, lower external knee flexion moments".].

  View details for DOI 10.1002/jor.25451

  View details for Web of Science ID 000875702900001

  View details for PubMedID 36205181

• Association Between the Functional Movement Screen and Landing Kinematics in Individuals With and Without Anterior Cruciate Ligament Reconstruction JOURNAL OF SPORT REHABILITATION Pamukoff, D. N., Holmes, S. C., Heredia, C. E., Gonzales, C. E., Shumski, E. J., Montgomery, M. M. 2022; 31 (7): 842-848

  Abstract

  The purpose of this study was to compare functional movement screen (FMS) scores and drop vertical jump (DVJ) kinematics between those with and without anterior cruciate ligament reconstruction (ACLR), and to evaluate the association between FMS composite score and DVJ kinematics.Cross-sectional.Sixty individuals with and without a history of ACLR.Composite FMS score and the dorsiflexion, knee-flexion, hip-flexion, knee abduction, hip adduction, and trunk-flexion angles during a DVJ.The FMS scores did not differ between groups (P > .05). There were smaller peak and initial contact hip-flexion angles in the ACLR and contralateral limbs compared with controls, and smaller peak dorsiflexion angles in the ACLR compared with contralateral limbs (P < .05). Lower FMS score was associated with a smaller peak dorsiflexion angle, smaller peak knee-flexion angle, and larger peak knee abduction angle in the ACLR limb (ΔR2 = .14-.23); a smaller peak dorsiflexion angle and smaller peak knee-flexion angle in the contralateral limb (ΔR2 = .17-.19); and a smaller peak dorsiflexion angle, smaller peak knee-flexion angle, and larger peak knee abduction angle in the control limb (ΔR2 = .16-.22).The FMS scores did not differ between groups, but were associated with DVJ kinematics and should be a complementary rather than substitute assessment.

  View details for DOI 10.1123/jsr.2021-0345

  View details for Web of Science ID 000874416300003

  View details for PubMedID 35413683

• Lower extremity coordination and joint kinetic distribution during gait in adults with and without Prader-Willi Syndrome JOURNAL OF BIOMECHANICS Pamukoff, D. N., Holmes, S. C., Garcia, S. A., Shumski, E. J., Rubin, D. A. 2022; 141: 111213

  Abstract

  Individuals with Prader-Willi Syndrome (PWS) have reduced mobility, which may be due to altered gait biomechanics. This study compared lower extremity intersegmental coordination and joint kinetics in adults with and without PWS. Walking biomechanics were evaluated in 10 adults with PWS and 10 controls without and 10 with obesity. The foot-shank and shank-thigh coordination was evaluated using modified vector coding and compared between groups using Kruskal-Wallis and Mann-Whitney U tests. The total support moment was summed from the ankle, knee, and hip extensor moments; and relative joint contributions were expressed as a percentage and compared between groups using one-way MANOVA. The group with PWS had greater exclusive shank segment rotation during later stance compared with controls with (p < 0.001) and without obesity (p < 0.001). The group with PWS also had a smaller absolute total support moment than controls with obesity during early and late stance (both p < 0.001), and lower normalized total support moment compared to controls without obesity during early stance (p = 0.019) and compared to controls with obesity during late stance (p = 0.004). Extensor moment contributions was similar between groups during early and late stance (all p > 0.05). Findings suggest a flat-footed gait pattern in PWS during late stance, which may negatively influence propulsion and speed. Moreover, those with PWS had lower total support moments than controls during early and late stance, but similar relative extensor contributions when walking at self-selected speeds. As such, improving overall torque generation in the lower extremity may be useful to improve stability and mobility during gait in PWS.

  View details for DOI 10.1016/j.jbiomech.2022.111213

  View details for Web of Science ID 000885841000004

  View details for PubMedID 35792406

• Knee extensor functional demand in individuals with knee osteoarthritis. Gait & posture Holmes, S. C., Boyer, K. A. 2022; 96: 265-270

  Abstract

  Knee extensor (KE) weakness is commonly exhibited in individuals with knee osteoarthritis (KOA) and may contribute to disability due an increased muscle functional demand and resulting compensatory gait strategies during locomotion. Muscle functional demand is defined as the percentage of maximal strength that is used during a task.The study aim was to quantify KE functional demand in KOA, the impact of walking speed and the relationships with the relative joint contribution to total limb work.Fourteen individuals with symptomatic KOA underwent gait analysis at preferred and faster speeds and isokinetic dynamometry for KE maximum voluntary isometric torque. The KE functional demand as well as the relative and peak joint work and powers were calculated. Paired samples t-test was used to compare functional demand and relative work between speeds and Pearson's correlation was used to assess the relationship between relative work and functional demand values (α = 0.05).The KE functional demand was 36.0 ± 15.7 % for the preferred speed and significantly higher at 49.8 ± 16.1 % for the faster speed, (t(13) = -5.45, p .05). Knee flexion moment was also significantly higher for the faster speed (t(13) = -5.54, p .001). There were significant relationships between fast speed functional demand and relative ankle negative power (r = -0.57) and relative ankle positive work (r = 0.66), (all p .05).The results suggest that as functional demand nears or exceeds 50 % of the muscle capacity individuals with KOA reduce the relative effort at the knee and use an ankle-based compensation strategy to meet task demands.

  View details for DOI 10.1016/j.gaitpost.2022.06.005

  View details for PubMedID 35709610

• Estimating Ground Reaction Force and Center of Pressure Using Low-Cost Wearable Devices IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Oubre, B., Lane, S., Holmes, S., Boyer, K., Lee, S. 2022; 69 (4): 1461-1468

  Abstract

  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.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.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.Normalized models accurately estimated GRF and CoP despite deficiencies in FSR data.Ambulatory use of the proposed system could enable objective, longitudinal monitoring of severity and progression for a variety of health conditions.

  View details for DOI 10.1109/TBME.2021.3120346

  View details for Web of Science ID 000792917400023

  View details for PubMedID 34648428

  View details for PubMedCentralID PMC8986131

• Association between quadriceps function, joint kinetics, and spatiotemporal gait parameters in young adults with and without obesity GAIT & POSTURE Vakula, M. N., Garcia, S. A., Holmes, S. C., Pamukoff, D. N. 2022; 92: 421-427

  Abstract

  Individuals with obesity have impaired gait and muscle function that may contribute to reduced mobility and increased fall risk.(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?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.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).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.

  View details for DOI 10.1016/j.gaitpost.2021.12.019

  View details for Web of Science ID 000792034300027

  View details for PubMedID 34973582

• The influence of body mass index and sex on frontal and sagittal plane knee mechanics during walking in young adults GAIT & POSTURE Garcia, S. A., Vakula, M. N., Holmes, S. C., Pamukoff, D. N. 2021; 83: 217-222

  Abstract

  Obesity and female sex are independent risk factors for knee osteoarthritis and also influence gait mechanics. However, the interaction between obesity and sex on gait mechanics is unclear, which may have implications for tailored gait modification strategies.The purpose of this study was to examine the influence of obesity and sex on sagittal and frontal plane knee mechanics during gait in young adults.Forty-eight individuals with (BMI = 33.03 ± 0.59; sex:50 % female; age:21.9 ± 2.6 years) and 48 without obesity (BMI:21.59 ± 0.25; sex:50 % female; age:22.9 ± 3.57 years) matched on age and sex completed over-ground gait assessments at a self-selected speed. Two (BMI) by two (sex) analysis of variance was used to compare knee biomechanics during the first half of stance in the sagittal (knee flexion moment [KFM] and excursion [KFE]) and frontal plane (first peak knee adduction moment [KAM], knee varus velocity [KVV]).We observed a BMI by sex interaction for normalized KFM (P = 0.03). Females had smaller normalized KFM compared to males (P = 0.03), but only in individuals without obesity. Males without obesity had larger normalized KFM compared to males with obesity (P = 0.01), while females did not differ between BMI groups. We observed main effects of sex and BMI group, where females exhibited greater normalized KAM (P < 0.01) and KVV (P < 0.01) compared to males, and individuals with obesity walked with greater KVV compared to those without obesity (P < 0.01). All absolute joint moments were greater in individuals with obesity (all P<0.01) and males had greater absolute KFM compared to females (P < 0.01).We observed sex differences in gait mechanics, however, KFM differences between males and females were only evident in individuals without obesity. Further, females and individuals with obesity had a larger KAM and KVV, which may contribute to larger medial compartment joint loading.

  View details for DOI 10.1016/j.gaitpost.2020.10.010

  View details for Web of Science ID 000604402600031

  View details for PubMedID 33171375

• Plantar Flexor Function in Adults with and without Prader-Willi Syndrome MEDICINE & SCIENCE IN SPORTS & EXERCISE Pamukoff, D. N., Holmes, S. C., Shumski, E. J., Garcia, S. A., Rubin, D. A. 2020; 52 (10): 2189-2197

  Abstract

  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.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 using one-way MANOVA. Associations between plantar flexor outcomes and gait speed were assessed using Pearson correlation in the PWS group.Adults with PWS had lower absolute and normalized early RTD, and lower H/M ratio than controls with and without obesity; lower absolute PT and late RTD than controls with obesity (all P < 0.05). Cross-sectional area, propulsive force, and plantarflexor moment were lower, and echo intensity was higher, in adults with PWS compared with controls without obesity (all P < 0.05). Greater absolute PT (r = 0.64), absolute early RTD (r = 0.62), absolute late RTD (r = 0.64), gastrocnemii CSA (r = 0.55), and propulsive force (r = 0.58) were associated with faster gait speed (all P < 0.05).Adults with PWS have impaired plantar flexor function likely attributable to reduced neuromuscular function and altered muscle morphology, which are associated with slower gait speeds.

  View details for DOI 10.1249/MSS.0000000000002361

  View details for Web of Science ID 000571968600015

  View details for PubMedID 32936593

• Body mass index moderates the association between gait kinetics, body composition, and femoral knee cartilage characteristics JOURNAL OF ORTHOPAEDIC RESEARCH Pamukoff, D. N., Vakula, M. N., Holmes, S. C., Shumski, E. J., Garcia, S. A. 2020; 38 (12): 2685-2695

  Abstract

  This study compared femoral cartilage characteristics between age- and sex-matched individuals with (n = 48, age = 22.8 ± 3.5 years; body mass index [BMI] = 33.1 ± 4.1 kg/m2 ) and without obesity (n = 48 age = 22.0 ± 2.6 years; BMI = 21.7 ± 1.7 kg/m2 ) and evaluated the associations between body composition, quadriceps function, and gait kinetics with femoral cartilage characteristics. Medial and lateral femoral cartilage thickness, medial:lateral thickness ratio and medial and lateral cartilage echo intensity were measured using ultrasound imaging. Body composition was assessed using air displacement plethysmography. Quadriceps function was assessed via maximal isometric knee extension. Three-dimensional gait biomechanics were recorded to extract peak external knee flexion and adduction moments, and peak loading rate of the vertical ground reaction force. Cartilage outcomes were compared between groups using one-way multivariate analysis of variance. Stepwise moderated regression evaluated the association between body composition, quadriceps function, and gait kinetics with femoral cartilage outcomes in individuals with and without obesity. Medial (75.24 vs 65.84; P < .001, d = 1.02) and lateral (58.81 vs 52.22; P < .001, d = 0.78) femoral cartilage echo intensity were higher in individuals with compared with those without obesity. A higher body fat percentage was associated with higher medial and lateral cartilage echo intensity (ΔR2  = 0.09-0.12) in individuals with obesity. A higher knee adduction moment was associated with a larger medial:lateral thickness ratio (ΔR2  = 0.09) in individuals without obesity. No associations were found between quadriceps function and cartilage outcomes. These findings suggest that high body fat in adults with obesity is associated with cartilage echo intensity. The obese body mass index was also associated with a lack of a positive relationship between cartilage thickness and joint loading during walking.

  View details for DOI 10.1002/jor.24655

  View details for Web of Science ID 000563518400001

  View details for PubMedID 32162713

• Quadriceps Muscle Size, Quality, and Strength and Self-Reported Function in Individuals With Anterior Cruciate Ligament Reconstruction JOURNAL OF ATHLETIC TRAINING Garcia, S. A., Moffit, T. J., Vakula, M. N., Holmes, S. C., Montgomery, M. M., Pamukoff, D. N. 2020; 55 (3): 246-254

  Abstract

  Ultrasound imaging provides a cost-effective method of measuring quadriceps morphology, which may be related to self-reported function after anterior cruciate ligament reconstruction (ACLR).To compare quadriceps morphology and strength between limbs in individuals with ACLR and matched control limbs and determine their associations with self-reported function.Cross-sectional study.Research laboratory.Forty-two individuals with ACLR (females = 66%; age = 21.8 ± 2.6 years; time since ACLR = 50.5 ± 29.4 months) and 37 controls (females = 73%; age = 21.7 ± 1.2 years).Quadriceps peak torque (PT) and rate of torque development were assessed bilaterally. Ultrasonography was used to measure the cross-sectional area (CSA) and echo intensity (EI) of the rectus femoris, vastus lateralis (VL), and vastus medialis. Self-reported function was assessed via the International Knee Documentation Committee (IKDC) score and Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales. Paired-samples t tests were calculated to compare involved and uninvolved limbs. Independent t tests were conducted to compare groups (α = .05). Linear regression was performed to analyze associations between quadriceps function and self-reported function after accounting for time since ACLR, activity level, and sex, and models for EI added subcutaneous fat as a covariate.Isometric PT did not differ between limbs or groups. Involved limbs had a lower rate of torque development compared with the control (P = .01) but not the uninvolved limbs (P = .08). Vastus lateralis CSA was smaller in the involved than in the uninvolved (P < .01) but not the control limbs (P = .10). Larger VL CSA (ΔR2 = 0.103) and lower VL EI (ΔR2 = 0.076) were associated with a higher IKDC score (P < .05). Larger VL CSA was associated with greater KOOS Symptoms (ΔR2 = 0.09, P = .043) and Sport and Recreation (ΔR2 = 0.125, P = .014) scores. Lower VL EI was associated with higher KOOS Symptoms (ΔR2 = 0.104, P = .03) and Quality of Life (ΔR2 = 0.113, P = .01) scores. Quadriceps PT and rate of torque development were not associated with IKDC or KOOS subscale scores.Quadriceps morphology was associated with self-reported function in individuals with ACLR and may provide unique assessments of quadriceps function.

  View details for DOI 10.4085/1062-6050-38-19

  View details for Web of Science ID 000521726900005

  View details for PubMedID 31951147

  View details for PubMedCentralID PMC7093934

• Quadriceps Impairment Is Associated with Gait Mechanics in Young Adults with Obesity MEDICINE & SCIENCE IN SPORTS & EXERCISE Vakula, M. N., Fisher, K. L., Garcia, S. A., Holmes, S. C., Post, B. K., Costa, P. B., Pamukoff, D. N. 2019; 51 (5): 951-961

  Abstract

  Obesity influences gait and muscle function, which may contribute to knee osteoarthritis. This study aimed 1) to compare gait biomechanics and quadriceps function between individuals with and without obesity and 2) to examine the association between quadriceps function and gait biomechanics.Forty-eight individuals with and 48 without obesity participated and were matched on age and sex. Gait biomechanics at standardized and self-selected speeds were used to assess peak vertical ground reaction force (vGRF), vertical loading rate (vLR), internal knee extension moment (KEM), peak knee flexion angle (KFA), knee flexion excursion (KFE), and knee joint stiffness. Quadriceps function was assessed using peak isometric strength (peak torque), early (RTD100) and late (RTD200) rate of torque development (RTD), and vastus lateralis cross-sectional area (CSA) and echo intensity (EI).When normalized to fat-free mass, individuals with obesity had lower RTD100 (P = 0.04) and RTD200 (P = 0.02) but higher vastus lateralis CSA (P < 0.01) and EI (P < 0.01) compared with normal weight controls. The group-speed interaction was significant for normalized vGRF (P < 0.01), normalized vLR (P = 0.02), normalized KEM (P = 0.03), and normalized knee joint stiffness (P = 0.02). Post hoc analyses indicate a smaller normalized vGRF and normalized KEM, and lower knee joint stiffness in individuals with obesity compared with normal weight controls at self-selected speed. There were main effects of speed for all kinematic and kinetic variables, and body mass index group for all absolute kinetic variables as well as normalized vGRF (all P < 0.001). A lower vastus lateralis EI (P = 0.04) and greater RTD100 (P < 0.01) were associated with a larger KEM in individuals with obesity.Individuals with obesity have quadriceps dysfunction that is weakly associated with KEM during walking. Exercise interventions that improve quadriceps function may improve walking mechanics.

  View details for DOI 10.1249/MSS.0000000000001891

  View details for Web of Science ID 000465009400014

  View details for PubMedID 30629047

• Association between gait mechanics and ultrasonographic measures of femoral cartilage thickness in individuals with ACL reconstruction GAIT & POSTURE Pamukoff, D. N., Montgomery, M. M., Holmes, S. C., Moffit, T. J., Garcia, S. A., Vakula, M. N. 2018; 65: 221-227

  View details for DOI 10.1016/j.gaitpost.2018.07.174

  View details for Web of Science ID 000441877300037