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Characterizing Longitudinal Alterations in Postural Control Following Lower Limb Injury in Professional Rugby Union Players

Molly F. McCarthy-Ryan, Stephen D. Mellalieu, Holly Jones, Adam Bruton, and Isabel S. Moore

Assessment of player’s postural control following a lower limb injury is of interest to sports medicine practitioners due to its fundamental role in daily tasks and sporting activities. The aim was to longitudinally monitor professional rugby union players’ postural control during each phase of the rehabilitation program (acute, middle, and late) following a lower limb injury. Seven male rugby union players (height 1.80 [0.02] m; mass 100.3 [11.4] kg; age 24 [4] y) sustained a time loss, noncontact lower limb injury. Static postural control was assessed via sway path (in meters), and dynamic postural control was assessed via vertical postural stability index. Group differences (P < .05) were reported across the acute, middle, and late phase. Smaller magnitudes of sway path were observed for eyes-open sway path, and for the middle and late phase smaller magnitudes of vertical postural stability index (P < .05) at the end session compared with first session. Whereas larger magnitudes of vertical postural stability index were found between baseline and the last session (P < .05). Large interindividual and intraindividual variation was apparent across the 3 phases of rehabilitation. Postural control improvements were identified during rehabilitation. However, postural control did not return to baseline, with altered kinetics throughout each rehabilitation phase.

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Effect of Data and Gap Characteristics on the Nonlinear Calculation of Motion During Locomotor Activities

Arash Mohammadzadeh Gonabadi, Thad W. Buster, Guilherme M. Cesar, and Judith M. Burnfield

This study investigated how data series length and gaps in human kinematic data impact the accuracy of Lyapunov exponents (LyE) calculations with and without cubic spline interpolation. Kinematic time series were manipulated to create various data series lengths (28% and 100% of original) and gap durations (0.05–0.20 s). Longer gaps generally resulted in significantly higher LyE% error values in each plane in noninterpolated data. During cubic spline interpolation, only the 0.20-second gap in frontal plane data resulted in a significantly higher LyE% error. Data series length did not significantly affect LyE% error in noninterpolated data. During cubic spline interpolation, sagittal plane LyE% errors were significantly higher at shorter versus longer data series lengths. These findings suggest that not interpolating gaps in data could lead to erroneously high LyE values and mischaracterization of movement variability. When applying cubic spline, a long gap length (0.20 s) in the frontal plane or a short sagittal plane data series length (1000 data points) could also lead to erroneously high LyE values and mischaracterization of movement variability. These insights emphasize the necessity of detailed reporting on gap durations, data series lengths, and interpolation techniques when characterizing human movement variability using LyE values.

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Osteoarthritic Tibiofemoral Joint Contact Characteristics During Weightbearing With Arch-Supported and Standalone Lateral Wedge Insoles

Calvin T.F. Tse, Michael B. Ryan, Natasha M. Krowchuk, Alexander Scott, and Michael A. Hunt

Imbalanced joint load distribution across the tibiofemoral surface is a risk factor for osteoarthritic changes to this joint. Lateral wedge insoles, with and without arch support, are a form of biomechanical intervention that can redistribute tibiofemoral joint load, as estimated by external measures of knee load. The objective of this study was to examine the effect of these insoles on the internal joint contact characteristics of osteoarthritic knees during weightbearing. Fifteen adults with tibiofemoral osteoarthritis underwent magnetic resonance imaging of the affected knee, while standing under 3 insole conditions: flat control, lateral wedge alone, and lateral wedge with arch support. Images were processed, and the surface area and centroid location of joint contact were quantified separately for the medial and lateral tibiofemoral compartments. Medial contact surface area was increased with the 2 lateral wedge conditions compared with the control (P ≤ .012). A more anterior contact centroid was observed in the medial compartment in the lateral wedge with arch support compared with the lateral wedge alone (P = .009). Significant changes in lateral compartment joint contact outcomes were not observed. These findings represent early insights into how loading at the tibiofemoral interface may be altered by lateral wedge insoles as a potential intervention for knee osteoarthritis.

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Volume 40 (2024): Issue 3 (Jun 2024)

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Muscle Torque–Velocity Relationships and Fatigue With Reduced Knee Joint Range of Motion in Young and Older Adults

Zoe H. Smith, R. Anthony Martin, Erica Casto, Carol Bigelow, Michael A. Busa, and Jane A. Kent

The purpose of this study was to evaluate the influence of knee joint range of motion (RoM) on the torque–velocity relationship and fatigue in the knee extensor muscles of 7 young (median = 26 y) and 7 older (68 y) adults. Each leg was assigned a RoM (35° or 75°) over which to perform a torque–velocity protocol (maximal isokinetic contractions, 60–300°·s−1) and a fatigue protocol (120 maximal contractions at 120°·s−1, 0.5 Hz). Six older participants were unable to reach 300°·s−1 over 35°. Therefore, the velocity eliciting 75% of peak torque at 60°·s−1 (V 75, °·s−1) was calculated for each RoM from a fit of individual torque–velocity curves (60–240°·s−1), and ΔV 75 (35°–75°) was determined. Fatigue (final torque/initial torque) was used to calculate Δfatigue (35°–75°). ΔV 75 was not different from 0 in young (−28.3°·s−1 [−158.6 to 55.7], median [range], P = .091) or older (−18.5°·s−1 [−95.0 to 23.9], P = .128), with no difference by age (P = .710). In contrast, fatigue was greater for 75° in young (Δfatigue = 25.9% [17.5–30.3], P = .018) and older (17.2% [11.9–52.9], P = .018), with no effect of age (P = .710). These data indicate that, regardless of age, RoM did not alter the torque–velocity relationship between 60 and 240°·s−1, and fatigue was greater with a larger RoM.

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Comparing Knee Kinetics and Kinematics in Healthy Individuals and Those With Knee Osteoarthritis, With and Without Flat Feet

Maryam Sohrabi, Giti Torkaman, and Fariba Bahrami

Individuals with knee osteoarthritis (KOA) and flat feet are more likely to experience increased pain and cartilage damage. This study aimed to investigate the knee kinetics, kinematics, pain, and physical function in individuals with moderate symptomatic KOA, in comparison to asymptomatic control participants. Thirty volunteers with moderate KOA (with flat feet n = 15, with normal feet n = 15) and 30 asymptomatic people (with flat feet n = 15, with normal feet n = 15) were evaluated. The knee adduction angular impulse, knee flexion moment, knee flexion angular impulse, and knee flexion angle were measured during level walking. The pain was assessed in patients with KOA. The study found that individuals with KOA had a significant increase in the knee adduction angular impulse compared with the asymptomatic people (P < .05). The KOA with flat feet group had significantly lower knee flexion moment, knee flexion angular impulse, and knee flexion angle values than the KOA with normal feet group (P < .05). Furthermore, the KOA with flat feet group had a higher pain score than the KOA with normal feet group. Individuals with osteoarthritis and flat feet had lower knee flexion moments which may indicate reduced knee force exerted through compensatory mechanisms. Despite this reduction, they reported significantly higher levels of pain compared with those without flat feet, a finding that warrants further investigation in future studies.

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Fourier Analysis of the Vertical Ground Reaction Force During Walking: Applications for Quantifying Differences in Gait Strategies

Taylor P. Trentadue and Daniel Schmitt

Time series biomechanical data inform our understanding of normal gait mechanics and pathomechanics. This study examines the utility of different quantitative methods to distinguish vertical ground reaction forces (VGRFs) from experimentally distinct gait strategies. The goals of this study are to compare measures of VGRF data—using the shape factor method and a Fourier series-based analysis—to (1) describe how these methods reflect and distinguish gait patterns and (2) determine which Fourier series coefficients discriminate normal walking, with a relatively stiff-legged gait, from compliant walking, using deep knee flexion and limited vertical oscillation. This study includes a reanalysis of previously presented VGRF data. We applied the shape factor method and fit 3- to 8-term Fourier series to zero-padded VGRF data. We compared VGRF renderings using Euclidean L2 distances and correlations stratified by gait strategy. Euclidean L2 distances improved with additional harmonics, with limited improvement after the seventh term. Euclidean L2 distances were greater in shape factor versus Fourier series renderings. In the 8 harmonic model, amplitudes of 9 Fourier coefficients—which contribute to VGRF features including peak and local minimum amplitudes and limb loading rates—were different between normal and compliant walking. The results suggest that Fourier series-based methods distinguish between gait strategies.

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The Midfoot Joint Complex (Foot Arch) Contributes to the Upper Body Position in Bipedal Walking and Coordinates With the Lower Limb Joints

Leonardo D. Barsante, Paula M.M. Arantes, Daniela V. Vaz, Fabricio A. Magalhães, Diego S. Carvalho, Aline C. Cruz, Renan A. Resende, Juliana M. Ocarino, Sérgio T. Fonseca, and Thales R. Souza

This study estimated the contribution of the midfoot joint complex (MJC) kinematics to the pelvis anterior–posterior positions during the stance phase of walking and investigated whether the MJC is functionally coordinated with the lower limb joints to maintain similar pelvic positions across steps. Hip, knee, ankle, and MJC sagittal angles were measured in 11 nondisabled participants during walking. The joints’ contributions to pelvic positions were computed through equations derived from a link-segment model. Functional coordination across steps was identified when the MJC contribution to pelvic position varied and the summed contributions of other joints varied in the opposite direction (strong negative covariations [r ≤ −.7] in stance phase instants). We observed that the MJC plantarflexion (arch raising) during the midstance and late stance leads the pelvis backward, avoiding excessive forward displacement. The MJC was the second joint that contributed most to the pelvis positions (around 18% of all joints’ contributions), after the ankle joint. The MJC and ankle were the joints that were most frequently coordinated with the other joints (≅70% of the stance phase duration). The findings suggest that the MJC is part of the kinematic chain that determines pelvis positions during walking and is functionally coordinated with the lower limb joints.

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Force–Time Characteristics of Repeated Bouts of Depth Jumps and the Effects of Compression Garments

Freddy Brown, Matt Hill, Derek Renshaw, and Jason Tallis

No studies have reported ground reaction force (GRF) profiles of the repeated depth jump (DJ) protocols commonly used to study exercise-induced muscle damage. Furthermore, while compression garments (CG) may accelerate recovery from exercise-induced muscle damage, any effects on the repeated bout effect are unknown. Therefore, we investigated the GRF profiles of 2 repeated bouts of damage-inducing DJs and the effects of wearing CG for recovery. Nonresistance-trained males randomly received CG (n = 9) or placebo (n = 8) for 72 hours recovery, following 20 × 20 m sprints and 10 × 10 DJs from 0.6 m. Exercise was repeated after 14 days. Using a 3-way (set × bout × group) design, changes in GRF were assessed with analysis of variance and statistical parametric mapping. Jump height, reactive strength, peak, and mean propulsive forces declined between sets (P < .001). Vertical stiffness, contact time, force at zero velocity, and propulsive duration increased (P < .05). According to statistical parametric mapping, braking (17%–25% of the movement) and propulsive forces (58%–81%) declined (P < .05). During the repeated bout, peak propulsive force and duration increased (P < .05), while mean propulsive force (P < .05) and GRF from 59% to 73% declined (P < .001). A repeated bout of DJs differed in propulsive GRF, without changes to the eccentric phase, or effects from CG.

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Volume 40 (2024): Issue 2 (Apr 2024)