Performance fatigability and neuromuscular responses for bilateral and unilateral leg extensions in men

OBJECTIVES: This study examined performance fatigability and the patterns of neuromuscular responses for electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) during bilateral (BL) and unilateral (UL) maximal, isokinetic leg extensions. METHODS: Peak torque for each repetition and EMG and MMG signals from the non-dominant vastus lateralis were recorded in 11 men during 50 BL and UL maximal, concentric, isokinetic leg extensions at 60(o)·(-1) that were performed on separate days. Separate repeated measures ANOVAs were performed to examine the normalized isokinetic torque and neuromuscular parameters. RESULTS: Normalized isokinetic peak torque demonstrated a significant Conditions by Repetition interaction (p<0.001, η(2)(p)= 0.594). There were no interactions, but significant main effects for Repetition with increases in EMG AMP (p<0.001; η(2)(p)=0.255) and decreases in EMG MPF (p<0.001; η(2)(p)=0.650), MMG AMP (p<0.001; η(2)(p)=0.402), and MMG MPF (p<0.001; η(2)(p)=0.796). In addition, EMG MPF and MMG AMP demonstrated main effects for Condition (p=0.031; η(2)(p)=0.387 and p=0.002; η(2)(p)=0.64, respectively) with the BL exhibiting greater values than UL leg extensions for both parameters. CONCLUSIONS: The current findings indicated greater performance fatigability during UL versus BL leg extensions, but similar patterns of neuromuscular responses consistent with the Muscle Wisdom Hypothesis.