Task-specific performance fatigability and the bilateral deficit during isokinetic leg extensions

OBJECTIVES: The purpose of the present study was to compare the fatigue-induced changes in performance fatigability, bilateral deficit, and patterns of responses for the electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF), during unilateral and bilateral maximal, fatiguing leg extensions. METHODS: Nine men (Mean±SD; age =21.9±2.4 yrs; height =181.8±11.9 cm; body mass =85.8±6.2 kg) volunteered to perform 50 consecutive maximal, bilateral (BL), unilateral dominant (DL), and unilateral non-dominant (NL) isokinetic leg extensions at 180°·s(-1), on 3 separate days. Electromyographic and MMG signals from both vastus lateralis (VL) muscles were recorded. Repeated measures ANOVAs were utilized to examine mean differences in normalized force, EMG AMP, EMG MPF, MMG AMP, MMG MPF and the bilateral deficit. RESULTS: The results demonstrated a Condition × Repetition interaction for normalized force (p=0.004, η(2)(p)=0.222) and EMG MPF (p=0.034, η(2)(p)=0.214) and main effects for Repetition for EMG AMP (p=0.019, η(2)(p)=0.231), MMG AMP (p<0.001, η(2)(p)=0.8550), MMG MPF (p=0.009, η(2)(p)=0.252), and the bilateral deficit (p<0.001, η(2)(p)=0.366). CONCLUSIONS: The findings demonstrated less performance fatigability during the BL than the unilateral tasks, likely due to a reduced relative intensity via interhemispheric inhibition that attenuated the development of excitation-contraction coupling failure during the BL task.