Search Results (44)

Background/Objectives: Running is associated with increased Achilles Tendon (AT) loading and cross-sectional area (CSA). Achilles tendinopathy is a common unilateral injury. Differences in AT loading variables between dominant and non-dominant lower extremities while running have not been characterized. This study examined the AT loading variables between dominant and non-dominant lower extremities in healthy recreational runners. Methods: Twenty-four females ran at 3.3 m/s (11.88 km/hr) on an instrumented treadmill. Achilles Tendon CSA (AT-CSA) was measured from ultrasound images. Kinematic and kinetic data were used as input into a musculoskeletal model. Paired t-tests examined inter-limb differences in peak vertical ground reaction force, Achilles Tendon-related loading variables (AT force, AT-CSA, AT stress), total gastrocnemius force, soleus force, foot strike angle, and stance time. Results: No differences were shown between dominant and non-dominant lower extremities in stance time, vertical ground reaction force, gastrocnemius and soleus force, AT force, AT-CSA, or AT stress. Foot strike angle was different between limbs (p = 0.015); however, the absolute difference was about 2°. Conclusions: These data indicated that AT loading was similar between dominant and non-dominant lower extremities in healthy female recreational runners. While some asymmetry can be expected during a bilateral task such as running, runners displayed differences in AT force and stress less than 18%. These data may assist clinicians in the assessment and management of runners recovering from AT tendinopathy. Full article

Background: Double-support percentage (DS%) is often interpreted as a proxy for dynamic gait stability, yet its biomechanical meaning is confounded by its strong inverse coupling with walking speed. This distinction is critical in Parkinson’s disease (PD), where bradykinetic gait inherently prolongs DS%. To isolate speed-independent stability demands, we introduced a model-based Stability Reserve Index (SRI), representing the deviation between predicted and observed double support after normalizing for velocity and anthropometrics. Methods: Using an open-access dataset of 63 individuals with PD (ON medication; Hoehn & Yahr 1–3) and 63 matched controls, step-based DS% was modeled using ANCOVA, incorporating centered walking speed, group, their interaction, and covariates. Predicted DS% at the sample’s grand mean speed was subtracted from observed DS% to derive the SRI, indexing whether double support exceeded expectations for a given biomechanical operating point. Results: PD participants walked slower than controls (p < 0.001), but once velocity was accounted for, DS% no longer differed between groups (p = 0.795–0.880), and the DS%–speed coupling remained intact (interaction p = 0.387). Speed-normalized predicted DS% (p = 0.159) and the SRI (p = 0.989) were likewise similar across groups. Within PD, SRI did not correspond to UPDRS-III or Hoehn & Yahr stage (ρ = 0.129–0.223, p > 0.05). Conclusions: These findings indicate that double-support behavior in mild-to-moderate PD is largely velocity-driven rather than reflecting altered dynamic stabilization strategies. While conceptually grounded in stability reserve theory, the SRI showed limited discriminatory value under ON-medication walking, suggesting that more sensitive multidimensional metrics—integrating CoM dynamics, variability, and step-to-step control—may be required to capture early instability in PD. Full article

Background/Objectives: While strength training interventions improve walking performance in stroke survivors, the underlying neuromuscular mechanisms remain poorly understood. This study investigated muscle-level adaptations following a 12-week moderate-to-high-intensity strength training program in ten chronic stroke survivors using comprehensive musculoskeletal modeling analysis. Methods: Three-dimensional gait analysis was performed pre- and post-intervention, with subject-specific OpenSim models estimating individual muscle forces, powers, and work capacities throughout stance phase. Results: Non-paretic hip flexor negative work capacity increased significantly (0.033 to 0.042 J/kg, p = 0.033, Cohen’s d = 0.47), driven by enhanced rectus femoris power absorption during late stance that mechanistically facilitated trunk acceleration through leg deceleration. Knee extensor force generation showed increasing trends during loading response in both limbs. During push-off, ankle plantar flexor force generation showed trends toward bilateral improvements, primarily through paretic soleus and gastrocnemius contributions, though power output remained unchanged, indicating persistent velocity-dependent muscular deficits. Conclusions: Improved gait performance in both limbs demonstrates that strength training produces functionally beneficial bilateral muscle-level reorganization. The absence of a control group limits causal inference, though the observed biomechanical adaptations align with functional improvements, supporting the integration of strength training into comprehensive stroke rehabilitation protocols targeting locomotor recovery. Full article

Background/Objectives: This study aimed to provide preliminary normative data on intersegmental coordination patterns during heel rises at different knee joint positions and across various phases and periods. Methods: Twelve 21-year-old university students from the same cohort performed heel rises in knee-extended and knee-flexed conditions. Shank and foot kinematics were recorded using the VICON Oxford Foot Model, and intersegmental coordination was analyzed using a modified vector coding technique. Results: The results showed that coordination patterns varied significantly between the ascending and descending phases and across the early, middle, and late periods. In the early ascending phase, knee extension exhibited in-phase coordination (shank external rotation with hindfoot inversion), resembling propulsion-related coordination in gait, whereas knee flexion displayed greater anti-phase coordination between hindfoot plantar flexion and forefoot dorsiflexion. The middle and late periods demonstrated heel-rise-specific patterns, with coordination shifting from proximal to distal dominance. Knee flexion altered the coordination between the shank and hindfoot and between the hindfoot and forefoot in the sagittal plane compared to that during knee extension. Conclusions: These findings suggest that the knee position influences intersegmental coordination during heel rises, and the present results provide reference values that can enable future diagnostic validation and comparative studies in pathological populations. Full article

Background: Some studies have suggested that physical fitness and body composition may influence individual and collective performance. However, it is necessary to be able to define the relationships between these variables in soccer players of different ages. Objective: To determine the relation between physical fitness level, body composition, and somatotype in female youth soccer players in response to age. Materials and methods: A total of 56 players were evaluated: 19 early adolescents (EA–U13) with a body mass of 48.35 ± 5.67 kg and a height of 157.63 ± 5.55 cm, 21 middle adolescents (MA–U15) with a body mass of 54.02 ± 5.96 kg and a height of 160.37 ± 5.25 cm and 16 late adolescents (LA–U17) with a body mass of 55.37 ± 6.15 kg and a height of 162.39 ± 5.77 cm. The physical fitness tests were: Squat Jump (SJ), Countermovement Jump (CMJ), Countermovement Jump with Arms (CMJA), Single Leg Countermovement Jump, COD-Timer 5-0-5, COD-Timer 5+5, Speed 15 m, Hamstring Strength, and Running-Based Anaerobic Sprint Test (RAST). The International Society for the Advancement of Kinanthropometry (ISAK) protocols were used to determine anthropometric measurements (skinfolds, circumferences, bone diameters), and the Heath-Carter method was used to assess body composition and somatotype, with z-scores calculated using the Phantom strategy. Results: The analysis revealed that the most significant differences between groups were observed in general anthropometric measurements (ω² = 0.84), followed by sitting height (ω² = 0.51) and percentage of body fat according to Carter’s method (ω² = 0.24), all with large and statistically significant effect sizes (p < 0.05). Larger muscle and bone dimensions, especially in the hip, thigh, and calf, are closely related to better strength, power, and initial sprint speed performance in female soccer players. Conclusions: This study reaffirms that muscle mass is a key predictor of athletic performance, along with strength at high speeds, promoting improvements in power and sprinting in the initial meters. Adiposity is a limiting factor for youth soccer players. Age progression and biological maturation favor the development of the mesomorphic profile, optimizing strength and power. Full article

Background/Objectives: The 2-minute walk test (2MWT) is a time-based gait assessment commonly employed for populations with limited walking ability for greater tolerability compared to the longer 6-minute test. The recommended distance to perform the tests is a 30 m straight path, a space requirement that is not always available in non-laboratory contexts. Shorter paths are therefore often adopted, but associated changes in gait patterns are not clear. The aim of the study is therefore to investigate how different walking path lengths affect gait patterns during the 2MWT. Methods: Twenty healthy young adults performed three walking trials on a straight hallway of 5 m, 15 m, and 30 m lengths. Spatiotemporal gait parameters were measured using three inertial measurement units on both distal tibiae and at pelvis level. Results: The 5 m path showed the greatest deviations, specifically in walking distance, walking speed, stride duration, stance time, swing time, single support time, and cadence, if compared to longer distances (p < 0.05). The 15 m path showed differences only in walking distance and walking speed (p < 0.05), if compared to the 30 m path. Conclusions: Shorter path lengths, particularly the 5 m, significantly impact gait patterns and should be considered when interpreting 2MWT results in clinical settings. The 30 m path is recommended as the gold standard, with 15 m as a viable alternative for assessing temporal parameters. Nevertheless, the extent to which each feature would be over/underestimated when walking in limited spaces is also addressed. Full article

Background/Objectives: Understanding how muscle fatigue contributes to musculoskeletal injuries is critical in sports science. Although joint biomechanics during landing under fatigue has been studied before, limited research has focused on the layup phase under fatigue. This study examined the effects of fatigue on ankle, knee, and hip-joint biomechanics during layup and landing. We hypothesized that fatigue would increase peak vertical ground reaction force (GRF), peak knee extension angle, and peak joint moments. Methods: Fourteen healthy male participants performed 3-step layups and drop landings using their dominant leg on force plates. The fatigue protocol consisted of squat jumps, step-ups, and repeated countermovement jumps (CMJs), with fatigue defined as three consecutive CMJs below 80% of the participant’s pre-established maximum jump height. After a fatigue protocol, they repeated the tasks. Kinematic data were collected using an eight-camera Vicon system (100 Hz), and GRF data were recorded with two AMTI force plates (1000 Hz). Thirty-six reflective markers were placed on lower-limb anatomical landmarks, and data were processed using Visual 3D. Paired t-tests ($\alpha$ = 0.05) were conducted using SPSS (V26.0) to compare pre- and post-fatigue outcomes. Results: Significant increases were found in peak GRF during landing (pre: 3.41 $\pm$ 0.81 BW [Body Weight], post: 3.95 $\pm$ 1.05 BW, p = 0.036), and peak negative hip joint work during landing (pre: $-$0.34 $\pm$ 0.18 J/kg, post: $-$0.66 $\pm$ 0.43 J/kg, p = 0.025). Conclusions: These findings indicate that fatigue may alter landing mechanics, reflected in increased ground reaction forces and negative hip joint work. These preliminary findings should be interpreted cautiously, and future studies with larger samples and additional neuromuscular measures under sport-specific conditions are needed to improve ecological validity. Full article

Background: Cluster sets (CSs) maintain velocity and power in compound movements by employing similar propulsion strategies or maintaining impulse through different mechanisms. This study aimed to explore the effect of four CS conditions on back squat (BS) propulsion and provide models for estimating changes in propulsion based on repetition and set number. Methods: Twenty male participants (age = 28.3 ± 3.1 years, stature = 1.74 ± 8.21 m, body mass = 84.80 ± 7.80 kg, BS 1RM = 140.90 ± 24.20 kg) completed four data collection sessions. Each session consisted of three sets of five repetitions at 80% 1RM BS with three minutes of unloaded inter-set rest, using varying intra-set rest intervals. Experimental conditions included 0 s (TRAD), 10 s (CS10), 20 s (CS20), and 30 s (CS30) inter-repetition rest, randomly assigned to sessions in a counterbalanced order. Ground reaction force data were collected on dual force platforms sampling at 1000 Hz, from which net propulsive impulse (J_PROP), mean force (MF), and propulsion time (t_PROP) were calculated. Conditions and sets were analysed using a 4 × 3 (CONDITION*SET) repeated-measures ANOVA to assess differences between conditions and sets, and linear mixed models (LMMs) were used to provide regression equations for each dependent variable in each condition. Results: The ANOVA revealed no significant interactions for any dependent variable. No main effects of CONDITION or SET were observed for J_PROP. The main effects of CONDITION showed that MF was significantly lower in TRAD than CS20 (g = 0.757) and CS30 (g = 0.749). t_PROP was significantly higher in TRAD than CS20 (g = 0.437) and CS30 (g = 0.569). The main effects of SET showed that MF was significantly lower in S2 (g = 0.691) and S3 (g = 1.087) compared to S1. t_PROP was significantly higher in S2 (g = 0.866) and S3 (g = 1.179) compared to S1. LMMs for CS20 and CS30 revealed no significant effect (p > 0.05) between repetition or set number and dependent variables. Conclusions: The results suggest that CS20 and CS30 maintain J_PROP by limiting MF and t_PROP attenuation. This is less rest than that suggested by the previous literature, which may influence programming decisions during strength and power mesocycles to maximise training time and training density. LMMs provide accurate estimates of BS propulsive force attenuation when separating repetitions by up to 30 s, which may help practitioners optimise training load for long-term adaptations. Full article

Multiple-hops performed horizontally in series effectively assess return-to-play readiness, as they mimic the propulsive and decelerative demands of sports. Movement strategy variables (kinetic variables) offer more insight into injury recovery than outcome-based measures (kinematic variables) like hop distance alone. This study focused on kinematic and kinetic variables to assess asymmetries during triple-hop (3-Hop) and quintuple-hop (5-Hop) tests with 44 male athletes from university sports clubs and teams. The aim was to determine the magnitude and potential direction of asymmetry and compare the sensitivity of kinematic and kinetic variables. Results showed mean kinematic asymmetries below 7.1% (range: 0.00 to 28.9%), while average kinetic asymmetries were as high as 38.8% (range: 0.0% to 95.4%). These findings suggest that kinetic variables are more sensitive in assessing movement strategy, providing more detailed insight into rehabilitation and return-to-play decisions. The study emphasizes the importance of considering both outcome and movement strategy variables in injury recovery. These results have practical applications for clinicians and coaches supporting those in return-to-play scenarios, as well as those addressing performance deficits, therefore offering valuable information to refine exercise prescriptions and athletic program design. Full article

Background: Increased hip-flexion gait (HFgait) has been shown to promote increased aerobic demands by increasing peak swing-phase hip-flexion angles while walking at comfortable speeds. Biomechanically, HFgait produces a gait pattern similar to walking, while removing the flight phase from running and reducing tibial accelerations. We sought to identify knee joint contact forces between HFgait and common exercise modalities, including running, walking, and cycling, across intensity levels. Methods: Ten healthy participants completed two bouts (low and high intensity) of four different exercises: treadmill running, walking, HFgait, and cycling. Tibiofemoral joint compressive force (TCF) was estimated using a static optimization-based approach. Results: Peak TCF was greater in running compared to HFgait, walking, and cycling; greater in HFgait compared to cycling; and greater in walking compared to cycling. The integral of TCF (iTCF) was greater in running compared to cycling, greater in HFgait compared to running, walking, and cycling, and greater in walking compared to running and cycling. Conclusions: HFgait produced lower knee joint loading than running, comparable joint loading to walking, and greater joint loading than cycling. Thus, HFgait may serve as an exercise modality for populations where joint loading is of particular concern, while achieving aerobic demands similar to running or increased functional demands compared to stationary cycling. Full article

Background/Objectives: The triple jump is included in the Paralympic Athletics competition. The aim of the research was to examine the relationship of the phase ratios and the inter-limb asymmetry in the spatiotemporal parameters of the approach run in Paralympic and international-level Class T46/T47 triple jumpers. Methods: Eleven Class T46/T47 male athletes were recorded during the examined competitions. Step length (SL), frequency (SF), and average velocity (ASV) for the late approach run as well as the length and the percentage distribution of each jumping phase (hop, step, jump) were measured using a panning video analysis method. The inter-limb asymmetry was estimated using the symmetry angle. Results: No significant inter-limb asymmetry was found (p > 0.05). In addition, SL, SF, and ASV were not different (p > 0.05) between the steps initiated from the ipsilateral and the contralateral leg regarding the impaired arm. However, the direction of asymmetry for SF was towards the ipsilateral leg to the impaired arm in the majority of the examined athletes. The maximum speed of the approach was correlated with the triple jump distance and the magnitude of asymmetry for AVS was correlated with the vertical take-off velocity and angle for the step. Conclusions: Since the distance of the triple jump related with the peak approach speed added the negative correlation of peak approach speed with the magnitude of the symmetry angle for SL, it is suggested to minimize the asymmetries in the step characteristics during the approach run to improve triple jump performance in Class T46/T47 jumpers. Full article

Purpose: Short-track speed skating results in high-energy crashes with an elevated risk of head injury. The goal of this study was to evaluate the resulting kinematics of an anti-rotation helmet technology for speed skating. Methods: Two traditional rigid foam speed-skating helmets (BT and ST) were compared with one anti-rotation speed skating helmet (MIPS). Each helmet was impacted with a pneumatic device across three locations. The resulting linear or rotational accelerations (PLA or PRA) and rotational velocities (PRV) were measured with accelerometers placed on a Hybrid III head form. Additionally, the head impact criterion (HIC) was calculated from accelerations and the brain injury criterion (BrIC) was obtained from rotational velocities. Results: MIPS showed significantly higher values of accelerations (PLA = 111.24 ± 9.21 g and PRA = 8759.11 ± 2601.81 rad/s²) compared with the other helmets at all three impact locations (p < 0.01, ES = 3.00 to 4.11). However, velocities were lowest, but not significantly different, for the MIPS helmet (25.77 ± 1.43 rad/s). Furthermore, all resulting kinematics except peak linear accelerations were significantly different across impact locations. Conclusion: Helmet designs specific to the collision characteristics of speed skating may still be lacking, but would decrease the risk of sport-related concussions. Full article

The purpose of this study was to compare average rate of oxygen consumption (VO₂), slow component of oxygen consumption (VO₂ drift), heart rate (HR) and rating of perceived exertion (RPE) while wearing compression pants vs. a control garment during long-distance running. Methods: Nine injury-free and recreationally active participants (32 ± 11 years) were recruited for this study. Participants ran in full-leg compression pants (COMP) and a loose-fitting control garment (CON). Participants ran in each condition for 40 min at a preferred submaximal speed. The rate of oxygen consumption (VO₂) was measured continuously via a metabolic cart throughout each condition. Both HR and RPE were recorded every 5 min during each condition. Oxygen consumption was averaged across the entirety of the steady state during the 40 min conditions for analysis. Additionally, the average from the first five minutes of the steady state was subtracted from the average of the last five minutes to assess VO₂. A paired t-test was used to assess for differences for both variables. Both HR and RPE were each compared between conditions using 2 (garment) × 8 (time) repeated measure ANOVAs (α = 0.05). Results: There were no differences between VO₂ or VO₂ drift while running with full-leg compression pants vs. the control garment (p > 0.05). Neither RPE nor HR were influenced by the garments (p > 0.05) or time (p > 0.05) during each condition. Conclusion: Wearing compression pants did not result in reduced VO₂, VO₂ drift, HR or RPE during a long-distance run. Although measured performance variables were not aided using compression pants, there were no negative effects to the use of compression pants. Full article

To the purpose of this study was to compare muscle oscillation, muscle activation time, and oxygen consumption while wearing compression pants vs. a control garment during running. Methods. Eleven injury-free and recreationally active participants (26.73 ± 12.74 years) were recruited for this study. Participants ran in full-leg compression pants (COMP) and a loose-fitting control garment (CON). Participants ran for 6 min at three submaximal speeds: preferred speed (PS), preferred speed minus 10% (PS − 10%), and preferred speed plus 10% (PS + 10%). The muscle activity of the leg was measured through electromyography (EMG). Muscle oscillation (MO) was measured with accelerometers attached to the thigh and shank. The rate of oxygen consumption ($\stackrel{.}{\mathrm{V}}$O₂) and heart rate (HR) were recorded during each condition. MO was assessed over the 0–60 Hz range by averaging power across 10 Hz bins per leg segment. EMG data was processed to identify the activation time. Following each condition, a belief score was recorded. Dependent variables were each compared between conditions using 2 (garment) × 3 (speed) repeated measure ANOVAs (α = 0.05). The relationship between the belief score and dependent variables (compression-control) was analyzed using Pearson’s product-moment correlation (α = 0.05). Results. MO was lower with the full-leg compression pants vs. the control garment (p < 0.05). The muscle activation time for each muscle was shorter while wearing the full-leg compression pants (p < 0.05). Neither the $\stackrel{.}{\mathrm{V}}$O₂, RPE, SF, nor the HR were influenced by the garments (p > 0.05). There was no significant correlation between changes in the dependent variables and belief. Conclusion. Wearing compression pants resulted in reduced MO and activation time; however, these changes did not translate into a reduction in $\stackrel{.}{\mathrm{V}}$O₂. Full article