Search Results (345)

Conventional gel electrodes are the gold standard for surface electromyography (sEMG), yet their bulkiness, stiffness, and limited gel lifetime prevents seamless day-long integration with wearable robots. We integrated ultrathin skin-conformal temporary tattoo electrodes with a powered unilateral hip exoskeleton and compared signal quality during treadmill walking against gel. In this pilot study, five healthy participants completed three consecutive walking blocks at fixed speed: (1) using gel electrodes; (2) using tattoo electrodes to compare signal quality; and (3) using the same tattoo electrodes (not repositioned) after eight hours of wear to simulate a full day of typical device use and to evaluate potential degradation in signal quality over time. Electrodes were positioned on muscles not covered by the exoskeleton interface (tibialis anterior and gastrocnemius medialis), as well as on muscles located beneath the exoskeleton cuff, which were potentially subject to motion artifacts due to the application of external forces by the exoskeleton (rectus femoris and biceps femoris, BF). Across all muscles, for both gel and tattoo electrodes, the root mean square error (RMSE) between normalized sEMG envelopes and biological activation profile was 0.069 ± 0.048, and Pearson’s correlation coefficient (ρ) was 0.844 ± 0.091. Re-testing the same tattoo electrode pair after eight hours confirmed day-long stability without the need for recalibration. Statistical analysis revealed no significant differences in signal quality, also when applying assistive forces, between the two electrode types and across all muscles (RMSE, all p ≥ 0.3125; ρ, all p ≥ 0.1250), as well as no degradation after eight hours (RMSE and ρ: all p ≥ 0.0626, uncorrected). Finally, in a proof-of-concept session, BF activity measured with tattoo electrodes was found reliable to drive hip-extension assistance in real time. Collectively, these results show that tattoo electrodes deliver signal quality comparable to gel electrodes while offering a low-profile skin-conformal interface and day-long usability, making them a promising option for enhancing EMG-based control in wearable robots. Full article

Objectives: Agonist–antagonist coordination is traditionally defined as simultaneous neural activation assessed by electromyography (EMG). The present study adopts a mechanical perspective, examining twitch-derived contractile ratio indexes between antagonistic muscle groups using tensiomyography (TMG). The aim was to determine whether sport expertise differentiates mechanical agonist–antagonist coordination in karate athletes. Methods: Fifty male participants were divided into four groups: elite karate athletes (EK; n = 7), national team members (NK; n = 14), basically trained karate practitioners (BK; n = 16), and physically active non-athlete controls (CG; n = 13). Bilateral TMG assessment of rectus femoris, vastus lateralis, vastus medialis, biceps femoris, and semitendinosus was performed. Contraction time (Tc), total contraction time (TcT), and rate of muscle tension development (RMTD) were extracted. Twelve twitch-derived contractile ratio indexes (CRI) were calculated separately for dominant (D) and non-dominant (ND) limbs. Results: Significant between-group differences were observed in the temporal coordination of the non-dominant leg. EK demonstrated the lowest index for average contraction time (CRI_Tc_AVG_ND = 17.13%; ANOVA p = 0.005; EK vs. NK p = 0.003) and total contraction time (CRI_TcT_AVG_ND = 9.72%; ANOVA p = 0.003; EK vs. NK p = 0.002). In contrast, velocity-related coordination in the dominant leg was highest in EK (CRI_RMTD_cV_D = 63.66%; ANOVA p = 0.002), differing from NK (p = 0.003), BK (p = 0.002), and CG (p = 0.009). Conclusions: Elite karate athletes exhibit distinct twitch-derived mechanical coordination profiles characterized by highly efficient temporal interplay in the non-dominant (supportive) limb and elevated velocity-related contractile ratio in the dominant (executive) limb. These findings suggest that sport expertise is associated with task-specific mechanical modulation between antagonistic muscle groups detectable through involuntary contractile responses. Full article

Background/Objective: Delaying muscle fatigue could alleviate economic and food security, and welfare concerns associated with transporting market-weight pigs to harvest. Previous research demonstrates barrow nicotinamide riboside (NR) supplementation at varying doses during the last 10 d of finishing shows to be a countermeasure to muscle fatigue by reducing muscle fiber recruitment and increasing mitochondrial DNA expression in a dose-dependent manner. Therefore, this study aims to determine if a greater NR dose further enhances barrow fatigue resistance and characterize muscle mitochondria content and efficiency. Methods: Barrows (N = 87) were assigned to one of two dietary NR supplementation doses (TRT): 0 (0NR) or 150 (150NR) mg/kg body weigh NR administered during the last 14 d of finishing. Muscle (MUS) biopsies were collected on supplementation d (DAY) 0, 7 and 14 from three hind-leg muscles for NAD+ quantification and mitochondrial DNA expression and efficiency. On days 15 and 16, barrows were subjected to a performance test until they were subjectively exhausted. Electromyography data collection during the performance test were divided into five periods (PER) and included normalized root mean square (nRMS) from the same muscles. Results: There were no three-way interaction for nRMS (p > 0.83), but there were MUS × TRT and PER × TRT interactions (p < 0.05). During performance testing, 150NR had greater nRMS than 0NR in the bicep femoris (BF) and tensor fasciae latae (TFL; p < 0.01), but there were no differences in the semitendinosus (ST; p = 0.77). Treatments did not differ during PER 1 and 2 (p > 0.14) but 150NR had greater nRMS than 0NR during PER 3, 4 and 5 (p < 0.01) across all muscles. There was no three-way interaction for normalized (nNAD+; p = 0.14), but there was a DAY × TRT interaction (p < 0.05). There were no differences between 0NR and 150NR at d 0 (p = 0.95); however, by d 7 and 14, 150NR muscles had greater nNAD+ than 0NR muscles (p < 0.01). There tended to be a three-way interaction for mitochondrial DNA expression (p = 0.09). At supplementation d 14, all 150NR muscles had greater mitochondrial DNA expression and electron transport chain complex I and II activities (p < 0.01). When normalized to citrate synthase activity, electron transport chain complex I and II activity did not differ (p > 0.05). Conclusions: Large-dose NR supplementation appears to support sustained muscle fiber recruitment during prolonged activity and enhance fatigue resilience, primarily through increased NAD+ and mitochondrial biomarkers abundance and not through mitochondrial efficiency. Full article

Background: Conditioning activity (CA) is used to elicit post-activation performance enhancement (PAPE), but it is unclear whether load response principles from back squat models generalize to unilateral split squat conditioning when external load and surface instability are manipulated together. Thus, the current study examined acute effects of stable vs. unstable split squat CA with or without external load on jump performance and phase-specific electromyography (EMG). Methods: Twenty men completed a randomized crossover of three CAs (2 × 3 reps): unloaded stable split squat (SS), unloaded BOSU SS, and BOSU loaded at 50% split squat one-repetition maximum. Single leg jump (SLJ) and countermovement jump (CMJ) were assessed pre-CA and at 3 min (SLJ) and 4 min (CMJ) post-CA. EMG was recorded from the biceps femoris (BF), semitendinosus (ST), vastus lateralis (VL), vastus medialis (VM) gluteus medius (Gmed), peroneus longus (PL), gastrocnemius lateralis (GL) and gastrocnemius medialis (GM). Signals were time-normalized across the split squat cycle and quantified using phase-specific area under the curve (AUC) (descending/ascending). Results: SLJ and CMJ increased after all conditions compared with the pre-test (p < 0.05). SS and unloaded BOSU SS produced comparable jump outcomes, whereas BOSU loaded yielded the greatest CMJ increase (p < 0.04). Unloaded BOSU SS selectively increased hamstring activation (BF, ST) without changes in Gmed or PL. BOSU loaded increased EMG amplitude across all measured muscles. Conclusions: External load primarily drives acute CMJ potentiation, whereas instability mainly redistributes recruitment toward the hamstrings without improving jump performance beyond the stable condition. These findings indicated that when the goal is acute jump enhancement, external load should be prioritized, whereas unstable surfaces may be used to selectively target posterior chain activation. Full article

This exploratory study determined the ideal ageing period for optimum tenderness of Longissimus thoracis et lumborum (LTL), Semimembranosus (SM) and Biceps femoris (BF) steaks from male and female giraffe. The muscles of eight male and seven female giraffes were divided into 10 steaks each, and each steak was randomly allocated to age for 1, 5, 9, 14, 18, 22, 26, 30, 34 or 38 days in vacuum-sealed bags at ±4 °C. At each time point, the pH, surface colour, purge loss, cooking loss and Warner–Bratzler shear force (WBSF) were determined for the respective steaks. Significant interactions between the sex, muscle and days post mortem were observed for the Warner–Bratzler shear force (WBSF), CIE a*, CIE b*, hue-angle, and chroma, while the CIE L* values were affected by an interaction between muscle type and days post mortem. The pH showed three distinct phases: over Days 1–9, the pH (~5.54–5.55) was stable; over Days 14–22, it declined; and the pH dropped more sharply between Days 22 and 26 (~5.42 to ~5.32), before plateauing. The purge loss initially increased rapidly, after which the rate decreased during the ageing period; however, the cooking loss, which was affected only by muscle, remained constant throughout. The tenderness improved until Day 22 across all three muscle types (19.1 ± 0.30 N), after which it plateaued. The colour improved, in terms of redness and saturation, until Day 18 (L* = 44.1 ± 0.29; a* = 15.7 ± 0.19; b* = 15.3 ± 0.08; hue-angle = 44.8 ± 0.39; chroma = 22.0 ± 0.15); thereafter, discolouration occurred. Vacuum-ageing giraffe meat for 14–22 days is recommended to improve tenderness and colour and minimise the negative effects of increased purge loss. This recommendation is based on instrumental measurements with discolouration as a major determinant of acceptability. It is suggested that future research validate this through sensory evaluation and microbial analyses. Full article

Valorisation of rabbit biodiversity plays a significant role in enhancing production by preserving genetic diversity, which is crucial for maintaining adaptability and resilience in rabbit populations, thereby supporting sustainable development and conservation efforts. With this in mind, the present research aimed at comparing live performance, carcass traits, meat quality and muscle fibre characteristics of different rabbit genotypes. Forty-five weaned rabbits (15 commercial hybrids—C; 15 Burgundy Fawn crosses—BF; 15 Vienna Blue crosses—VB) were farmed until slaughter (n = 15 replicated cages/rabbit genotype). The slaughter age was scheduled when all genotypes reached the same live weight (approx. 2800 g). After slaughtering and carcass dissection, the hind legs and longissimus lumborum muscles were excised and subjected to different evaluations. Hind legs were exploited for physicochemical analyses, while longissimus lumborum muscles were used for physical evaluations and for fibre typing, morphometric traits and enzymatic activity. As a direct response to the experimental design, results highlighted that the three genotypes exhibited different slaughter ages. Commercial hybrids displayed the fastest growth cycle, but they showed an efficiency comparable to that of VB crosses (p > 0.05). Genotypes displayed some differences in carcass characteristics, namely perirenal fat (p < 0.01) and hind leg weight (p < 0.05). The physical characteristics of meat were overall similar in the three genotypes, except for biceps femoris L*, which showed the highest value in the BF group. Meat chemical composition differed depending on the genotype, with BF rabbits having the highest ether extract (p < 0.05) content. The three genotypes displayed an overall similar fatty acid profile with some minor differences: VB rabbits had the highest C18:2 n-6 proportion (p < 0.01) and thus n-6/n-3 (p < 0.05). Cholesterol content was the highest in C rabbits (p < 0.05). Overall, the present research highlighted that BF and VB genotypes provided interesting potentialities which would be further valorised in rural farming conditions, given their higher resilience and adaptability than commercial hybrids. Full article

Background: Falls are a leading cause of injury and mortality worldwide. Higher physical activity levels in young adults may increase exposure to fall-related situations. Understanding their neuromuscular adaptations is critical for balance control research and perturbation-based training. This study examined proactive and reactive adaptations in lower-limb muscle activity during repeated simulated trips among young adults. Methods: Twenty participants experienced five treadmill-induced standing-trips. Bilateral electromyography (EMG) activities of the rectus femoris (RF), vastus lateralis (VL), tibialis anterior (TA), medial gastrocnemius (MG), and biceps femoris (BF) were recorded. Muscle activity magnitude at perturbation onset (ON), EMG peak amplitude, and time-to-peak from ON were extracted and compared across trials. Results: Proactive activation at ON increased across trials in TA and RF on the recovery side (p = 0.012–0.023) and in TA, VL, and BF on the stance side (p = 0.002–0.034). Reactive peak amplitudes decreased in RF, VL, and BF on the recovery side (p < 0.001–0.014) and in RF, VL, and BF on the stance side (p < 0.001–0.016). Time-to-peak shortened in MG, RF, VL, and BF on the recovery side (p < 0.001–0.030) and in RF, VL, TA, and BF on the stance side (p < 0.001–0.050). Conclusions: Repeated simulated trips elicited proactive adaptations in muscle activity and reactive changes in time-to-peak, which may suppress the need for increased reactive muscle activations to recover balance post-perturbation over trials in young adults. The findings augment our understanding of the intercorrelation between proactive and reactive adaptations to repeated perturbations. Full article

Time–frequency (TF) characterization of electromyographic (EMG) bursts is essential for accurately assessing muscle function, particularly when the signals exhibit a high degree of nonstationarity. In this exploratory study, we investigated the temporal dynamics of the spectral components associated with short-latency EMG bursts using several TF analysis techniques. Specifically, we compared the performance and interpretability of spectrograms obtained via the short-time Fourier transform (STFT), the continuous wavelet transform (CWT), and noise-assisted multivariate empirical mode decomposition (NA-MEMD), applied to EMG signals recorded from the biceps femoris muscle of freely moving rats in an animal model of Parkinson’s disease, acquired using chronically implanted bipolar electrodes during treadmill locomotion. For each method, we evaluated its effectiveness in capturing transient variations in frequency content, the stability of extracted features across bursts, and the extent to which these features reflect physiologically meaningful aspects of muscle activation. The results show that TF approaches reveal complementary information about burst structure; NA-MEMD provides greater adaptability to nonlinear and nonstationary components, whereas STFT- and CWT-based representations offer more controlled and comparable analyses. Overall, these findings highlight the value of TF analysis as a methodological tool for evaluating muscle function and provide a solid foundation for selecting analytical strategies in studies where EMG bursts exhibit complex and highly variable spectral profiles. Full article

Background: Age-related differences in neuromuscular coordination during multi-joint tasks are reported, but phase-specific evidence during maximal sprinting is limited. Aim: The aim of this study was to investigate phase-specific age differences in agonist–antagonist coordination of the biarticular thigh muscles during 50 m sprinting. Methods: Thirty-eight healthy trained track athletes (Adults: n = 21, age = 23.32 ± 2.98 years; Adolescents: n = 17, age = 13.65 ± 0.76 years) performed maximal 50 m sprints over force plates. Bilateral rectus femoris (RF) and biceps femoris (BF) sEMG and ground reaction forces were recorded; each stride was segmented into seven phases, and an RF–BF co-contraction index (CCI) was calculated per phase. Between-group differences in phase mean CCI were tested (α = 0.05) and quantified with Hedges’ g. Speed- and frequency-dependent modulation of CCI was evaluated using linear mixed-effects models (LME; random intercepts for participant) with Frequency × Group and Speed × Group interaction terms; ordinary least squares (OLS) fits on stride cycle-level group means were descriptive. Linear and single-breakpoint segmented models were compared using the corrected Akaike information criterion (AICc) and Akaike weights. Results: Adolescents showed higher CCI in contact (right: Adults 0.09 ± 0.05 vs. Adolescents 0.13 ± 0.07, g = 0.68; left: Adults 0.08 ± 0.04 vs. Adolescents 0.12 ± 0.06, g = 0.84) and propulsive phases (right: Adults 0.08 ± 0.05 vs. Adolescents 0.13 ± 0.08, g = 0.68; left: Adults 0.07 ± 0.04 vs. Adolescents 0.12 ± 0.07, g = 0.84; p < 0.05 for both legs in both phases). LME identified Frequency × Group interactions in the stride cycle (ΔSlope = 0.10, p < 0.001) and late swing (ΔSlope = 0.12, p < 0.05) and a Speed × Group interaction in mid swing (ΔSlope = 0.01, p < 0.05). Mid swing showed a positive CCI–speed/frequency relationship in both groups, whereas across most other phases Adults downregulated CCI as speed/frequency increased while Adolescents tended to increase CCI. Model selection supported phase-dependent single-breakpoint patterns, with breakpoints around 2.19–2.21 Hz and 6.11–9.51 m·s⁻¹ in Adults and around 2.11 Hz and 7.13–7.59 m·s⁻¹ in Adolescents. Conclusions: Maximal sprinting revealed phase-specific age differences in BF–RF co-contraction and its scaling with speed/frequency, which may help guide age-informed monitoring and training considerations in developing athletes. Full article

Objective: We examined vastus lateralis (VL), gastrocnemius medialis (GM), gastrocnemius lateralis (GL), and biceps femoris (BF) muscle architecture and force–time parameters recorded during a countermovement jump (CMJ). Methods: Eighty-nine 9 year-old girls (43 rhythmic gymnasts and 46 recreationally active controls) were assessed in: (a) muscle architecture (fascicle length—FL; angle; muscle thickness; and anatomical cross-sectional area—CSA) using ultrasonography, (b) CMJ performance (maximum force—Fmax; rate of force development—RFD; jump height; and peak power) using force–time data, and (c) anthropometrics and body composition. Results: Rhythmic gymnasts exhibited greater BF fascicle length and muscle thickness than controls (7.84 ± 0.73 vs. 7.26 ± 0.75 cm and 1.76 ± 0.19 vs. 1.61 ± 0.22 cm, respectively, p < 0.001), while VL muscle CSA was larger in controls (p = 0.001). When normalized to the respective segment length (thigh or shank), the FL was longer in gymnasts across all muscles (p ≤ 0.017). Gymnasts also demonstrated greater CMJ height (13.1%, p = 0.005), power scaled to body mass, and RFD (p < 0.005), while controls produced a greater Fmax (16.9%, p = 0.002). Body mass was the strongest predictor of Fmax in both groups (p < 0.001). CMJ power was best predicted by gastrocnemius CSA in gymnasts and by VL CSA combined with maturity offset in controls (all p < 0.001). Maturity offset and gastrocnemius CSA also predicted allometrically scaled power in controls. Conclusions: Rhythmic gymnasts are characterized by muscle-specific adaptations, specifically in the BF muscle FL and muscle thickness, which favor superior CMJ performance. In developing athletes, body mass is primarily related to maximal force, whereas muscle CSA is more closely associated with power output. Full article

Background: Diabetes-related foot complications are among the most common complications in individuals with type 2 diabetes mellitus. The prevention of foot problems that are at risk of developing because of type 2 diabetes mellitus should be addressed within the framework of preventive approaches prior to treatment. The aim of this study was to evaluate protective sensation in people with type 2 diabetes mellitus who have not been diagnosed with early diabetes-related foot complications and to investigate the effects of protective sensation on peripheral muscle strength, balance, and functional capacity. Methods: This study included 42 volunteer patients (56.71 ± 7.59 years) who were followed up with a diagnosis of type 2 diabetes mellitus and met the inclusion criteria. Individuals were evaluated prospectively and via face-to-face interviews. Light-touch, vibration, and discrimination sense was evaluated to determine protective sensation. Peripheral muscle strength (quadriceps femoris, biceps brachii, and hand grip) was measured and a 6 min walking test for functional capacity and balance evaluation were performed. Spearman correlation analysis was conducted using SPSS Statistics 21.0 for data analysis. Results: At least one of the components of protective sensation was moderately correlated with peripheral muscle strength, functional capacity, and balance scores. Reduced protective sensation was also observed in individuals with type 2 diabetes mellitus without neuropathy. Conclusions: In type 2 diabetes mellitus patients, decreases in light-touch, vibration, and discrimination sense are moderately associated with parameters of peripheral muscle strength, functional capacity, and balance. In patients with type 2 diabetes mellitus, early foot sole sensory examination may prevent the development of neuropathy and support clinicians in early diagnosis. Full article

Background and Objectives: Sarcopenia is a common yet underrecognized condition in cancer patients and is associated with increased treatment-related toxicity, functional decline, and poor clinical outcomes. Practical, rapid, and bedside-applicable tools are needed to detect sarcopenia early in routine oncology practice. This study aimed to evaluate the diagnostic value of rectus femoris muscle ultrasonography within an integrated clinical assessment combining handgrip strength and bioelectrical impedance analysis for the detection of sarcopenia in cancer patients. Materials and Methods: In this prospective cross-sectional study, 147 adult patients with malignancy were evaluated using a multimodal sarcopenia assessment framework. Muscle strength was assessed by handgrip dynamometry, muscle mass was estimated using bioelectrical impedance analysis (BIA)-derived appendicular skeletal muscle mass index (ASMI), and muscle morphology was evaluated using ultrasonographic measurements of the rectus femoris and biceps brachii muscles. Sarcopenia was defined and classified according to the EWGSOP2 criteria. Associations between clinical variables, BIA parameters, and ultrasonographic measurements were analyzed. Receiver operating characteristic (ROC) curve analyses were performed to assess the diagnostic performance of muscle ultrasonography for sarcopenia detection. Results: The mean age of the study population was 60.2 ± 11.2 years, and 51% of participants were male. Confirmed sarcopenia was identified in 12.2% of patients, while 27.2% were classified as having probable sarcopenia. Sarcopenic patients were significantly older (68.5 ± 7.6 vs. 59.0 ± 11.2 years, p = 0.001) and had lower handgrip strength (15.8 ± 6.0 vs. 24.3 ± 8.4 kg, p < 0.001) and ASMI values (5.96 ± 0.64 vs. 7.23 ± 1.18 kg/m², p < 0.001). Rectus femoris muscle thickness was significantly reduced in patients with sarcopenia (6.40 ± 1.42 vs. 8.19 ± 2.21 mm, p = 0.001). Rectus femoris muscle thickness demonstrated good diagnostic performance for sarcopenia detection (AUC = 0.752; 95% CI: 0.650–0.853; p = 0.001), with an optimal cut-off value of ≤7.59 mm (sensitivity 83.3%, specificity 61.2%). Conclusions: Rectus femoris muscle ultrasonography is a practical, rapid bedside assessment for detecting sarcopenia in cancer patients. When integrated with handgrip strength and BIA, this multimodal approach provides a feasible, radiation-free strategy for early sarcopenia screening in routine oncology practice. Full article

Background: Knee osteoarthritis (KOA) often results in reduced physical activity. This exploratory study evaluated lower limb muscle activity across three e-cycling assistance levels and examined e-cycling’s influence on kinesiophobia, stress and exercise motivation in individuals with KOA. Methods: Ten participants cycled with no, low and high assistance on an e-bike. Muscle activity and knee kinematics were measured using surface electromyography and inertia measurement units. A subset of four participants completed questionnaires assessing kinesiophobia (TSK-17), perceived stress (PSS), and exercise motivation (BREQ-3). Muscle activity across the three levels of assistance was analysed using a linear mixed-effects model. Results: Peak and mean muscle activity of rectus femoris (p = 0.01; 0.039), vastus medialis oblique (p = 0.0002; 0.001) and biceps femoris (p = 0.002; 0.03) were lower during high-assistance compared to the no-assistance cycling. No significant differences were observed in mean muscle activity between no- and low-assistance cycling. Reported exertion and pain were low during e-cycling, with kinesiophobia (M = 35.8 ± 2.5 to 33.3 ± 3.5) decreasing following e-cycling, whereas perceived stress (M = 14 ± 5.7 to 14.5 ± 3.3) increased marginally in our small sample. In the small subgroup of participants, the Behaviour Regulation Exercise Questionnaire outcomes increased in four out of six subscores post-exercise. Conclusions: Considering the differences in muscle activity recorded, and given that this is a pilot study, we propose that e-cycling may be an ideal way of introducing graded exercise to KOA patients, potentially allowing them to maintain physical activity and self-management of their disease. Full article

Background/Objectives: Knee osteoarthritis (KOA) is associated with pain, functional decline, and altered biomechanics. The Step-Up and Down-Forwards (StUD-F) task provides an ecologically relevant assessment of challenging movements. This study investigated neuromuscular activation and lower-limb kinematics of leading and trailing-limbs during the StUD-F in individuals with KOA. Methods: Forty participants with KOA (65.3 ± 7.68 years; 21M/19F; BMI 28.9 ± 4.52 kg/m²) completed a 25 cm box StUD-F task. Surface electromyograph recorded bilateral activation of the vastus medialis (VM), vastus lateralis (VL), bicep femoris (BF), and semitendinosus (ST). Triplanar hip, knee, and ankle joint angles were estimated using inertial measurement units. StUD-F events (initial stance; step contact; ascent completion; descent preparation; step-down touchdown; and descent completion) were identified using custom algorithms. Pain was assessed using visual analogue scales and the Knee Injury and Osteoarthritis Outcome Score (KOOS). Limb differences were analysed for leading or trailing roles using paired samples t-tests or non-parametric equivalents; waveforms were visually inspected. Results: Distinct neuromuscular and kinematic asymmetries were observed when affected and contralateral limbs were compared within each role (leading/trailing). During step-up, the affected leading limb demonstrated higher quadriceps activation at initial stance (VM: p = 0.035; VL: p = 0.027) and reduced trailing-limb activation at step contact (VM: p = 0.015; VL: p = 0.018), with sagittal-plane ankle differences (p = 0.004). During step-down, when the affected limb initiated ascent, trailing limb activation was higher at descent completion (VL: p < 0.001; VM: p = 0.003; BF: p = 0.009), with coronal-plane hip deviations (p < 0.001). When the contralateral limb-initiated ascent, trailing-limb muscles activation differences (VM: p < 0.001; VL: p = 0.015; BF: p = 0.007) and ankle/coronal-plane asymmetries (p ≤ 0.049) persisted. Conclusions: The StUD-F task elicits altered strategies in KOA, including elevated quadriceps–hamstring co-activation and altered sagittal/coronal alignment, and habitual limb choice across ascent and descent. These adaptations may enhance stability and joint protection but could increase medial compartment loading. The findings support rehabilitation focused on dynamic control, alignment, and shock absorption. Full article

This study examined fatigue- (within-group) and sex-related (between-group) differences in physical performance and muscle activation during physical assessments. Physically active college students (20 males, 20 females) completed side-hop and pelvic stability tests after a warm-up (T-1) and mobilization exercises (T0) and then following each with five 8 min runs at 70% of individualized peak velocity as the fatiguing protocol (T1–T5). No significant within-group performance differences were observed across tests (T0–T5). However, males completed more hops (p < 0.001) and had shorter ground contacts (p < 0.05) than females in the side-hop test with no significant sex-based stability differences. Electromyography data revealed reduced activation (p < 0.05) in various muscles (gastrocnemius, vastus medialis, biceps femoris, gluteus medius, gluteus maximus, erector spinae, obliquus abdominis) under fatigue (various timepoints between T1–T5) compared to baseline (T-1) across tests. Males displayed greater relative reductions in activation (p < 0.01) from pre-activation to ground contact in the gastrocnemius and biceps femoris during the side-hop test. Females exhibited reduced vastus medialis (p = 0.02) activation during the side-hop test and reduced biceps femoris (p = 0.04) activation during the pelvic stability test than males. Physical performance remained stable under fatigue, with sex-specific muscle recruitment strategies appearing as possible compensatory mechanisms. Full article