quads

<h4>Background</h4>Low-load blood-flow restriction training (BFR-LIR) can enhance strength-related adaptations with reduced mechanical stress, but whether it promotes task-related neuromuscular economy (lower task-related sEMG amplitude for comparable mechanical output) and how it compares with high-intensity resistance training (HIR) remains unclear.<h4>Objective</h4>To compare the effects of 4 weeks of BFR-LIR, HIR, and LIR on isokinetic knee extensor performance, task-related neuromuscular activation, functional performance, and perceived exertion in healthy young men.<h4>Methods</h4>Twenty-four healthy young men were randomized (1:1:1) to a low-load blood-flow restriction training group (BFR-LIR; ∼30% baseline isokinetic peak torque with individualized cuff pressure set at 70% arterial occlusion pressure [AOP] using a 10-cm pneumatic cuff), a high-intensity resistance training group (HIR; 8-12 RM), or a low-intensity resistance training group (LIR; ∼30% baseline isokinetic peak torque). All groups trained three times per week for 4 weeks. Outcomes were assessed pre- and post-intervention (isokinetic knee extensor peak torque at 60°/s and 120°/s, quadriceps sEMG during standardized isokinetic testing, countermovement jump and standing long jump performance, and ratings of perceived exertion). Between-group effects were evaluated using one-way ANOVA on Pre-Post change scores (Δ) with Holm-adjusted <i>post hoc</i> comparisons, and effect sizes were reported. RPE was recorded immediately after the standardized isokinetic testing protocol (not during the jump tests).<h4>Results</h4>Peak torque did not significantly change from pre-to post-intervention in any group at either velocity. Between-group comparisons of change scores (Δ) identified a significant group effect for Total Work at both 60°/s and 120°/s, driven by larger increases in HIR than LIR. Within-group Total Work increased at 60°/s in BFR-LIR and HIR, and at 120°/s in HIR. In BFR-LIR, Mean %MVC and dynamic RMS during isokinetic testing decreased at both velocities, whereas no consistent changes were observed in HIR or LIR. Hang time improved in HIR; standing long jump and RPE were unchanged across groups. No training-related adverse events were reported.<h4>Conclusion</h4>Over 4 weeks, BFR-LIR was associated with small within-group improvements in isokinetic total work at 60°/s and reduced task-related quadriceps sEMG during isokinetic testing, whereas HIR showed the clearest improvement in hang time. Between-group differences in ΔsEMG were not significant, and changes did not translate to multi-joint jump performance over the short intervention period.

matched text: “quadriceps”

<h4>Background</h4>Neuromuscular fatigue can be characterized by an exercise-induced reduction in force-generating capacity involving both neural and muscular mechanisms. Previous research has suggested that the functional organization of the neuromuscular system differs between endurance-trained individuals and sedentary or recreationally active individuals. This difference may lead to distinct neuromuscular responses to fatigue. The aim of this study was to compare neuromuscular fatigue responses between endurance-trained (ET) and recreationally active (RA) males during a sustained submaximal isometric knee extension contraction.<h4>Methods</h4>Eleven ET and 11 RA participants performed maximal voluntary isometric contractions (MVIC) of the knee extensors (KE), followed by a trapezoidal contraction (ascending to 60% MVIC) and an isometric fatiguing task at 30% MVIC sustained to task failure. An additional MVIC was completed immediately post-fatigue task. High-density surface electromyography (HDsEMG) was simultaneously recorded from the vastus lateralis, and HDsEMG root mean square (RMS), median frequency (MDF) and muscle fibre conduction velocity (MFCV) were estimated. The MFCV-torque relationship during the ascending phase of the trapezoidal contraction (up to 60% MVIC) was assessed using the mixed linear model.<h4>Results</h4>Baseline MVIC of the KE did not differ between groups. The ET group showed a significantly lower rate of increase in MFCV (<i>p</i> < 0.001) during the ascending phase of the contraction and lower absolute MFCV at 60% MVIC (<i>p</i> < 0.001) compared to the RA group. During the sustained fatiguing task, both groups reached task failure at similar times with comparable MVIC reductions (∼25%). However, the RA group exhibited significant declines in both MDF (<i>p</i> < 0.001) and MFCV (<i>p</i> = 0.04), whereas these parameters remained unchanged in the ET group.<h4>Conclusion</h4>While ET and RA individuals exhibited similar levels of fatigue, the underlying neuromuscular mechanisms may differ. The ET group showed a lower rate of increase in MFCV with increasing voluntary force and unchanged MFCV and MDF during fatiguing contractions, whereas the RA group exhibited fatigue-induced decreases in both MFCV and MDF. These findings suggest that endurance training is associated with altered recruitment and/or muscle membrane properties, likely linked to differences in muscle fibre characteristics.

matched text: “vastus lateralis”