Fatiguing, Unilateral, Maximal Intended Velocity Leg Extensions Do Not Affect the Performance of the Contralateral Limb.

Roberts, TD, Arnett, JE, Pioske, JS, Ortega, DG, Schmidt, RJ, and Housh, TJ. Fatiguing, unilateral, maximal intended velocity leg extensions do not affect the performance of the contralateral limb. J Strength Cond Res XX(X): 000-000, 2026-This study examined changes in performance and neuromuscular outcomes in a working and nonworking limb from a fatiguing, unilateral, maximal intended velocity (MIV) task. Twelve recreationally active men performed unilateral, MIV leg extensions to failure at 40% 1-repetition maximum with the working limb (initial repetition = PRE; final repetition = POST). The nonworking limb performed 2 unilateral, MIV repetitions before (PRE = highest velocity repetition) and after (POST = highest velocity repetition) the fatiguing task. Mean and peak force, velocity, and power were collected with a linear transducer. Normalized (to PRE) electromyographic amplitude (EMG AMP), mean power frequency (EMG MPF), and neuromuscular efficiency (NME = mean force/EMG AMP) were calculated for both limbs' rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM). Separate 2-way (Repetition × Limb) and 3-way (Repetition × Limb × Muscle) repeated-measures ANOVAs were used to analyze the performance and neuromuscular outcomes, respectively. The significance level was p ≤ 0.05. All performance outcomes decreased (p < 0.001) PRE to POST for the working limb but not (p = 0.177-0.942) the nonworking limb. Collapsed across Limb and Muscle, EMG AMP increased (p < 0.001) from PRE to POST. There were no changes (p = 0.351-0.818) in EMG MPF for all muscles of the nonworking limb, but for the working limb, the RF exhibited a greater (p < 0.001) decrease than the VL and VM. Collapsed across Muscle, NME decreased (p < 0.001) for the working limb but not (p = 0.545) the nonworking limb. The decrease in performance for the working limb was likely due to peripheral fatigue, which was muscle-specific (RF fatigue > VL/VM fatigue). Despite an increase in EMG AMP, the performance of the nonworking limb was unaffected.