Mode-specific Differences In Exercise-induced Fatigability And The Bilateral Deficit During Isokinetic Leg Extensions In Women.

Abstract

Exercise-induced fatigability (EF) is defined as a fatigue-induced decline in force production and has been reported to exhibit mode-specific differences where unilateral (UL) tasks exhibit greater EF than bilateral (BL) tasks. While women have been reported to display a greater resistance to fatigue than men, few studies have examined whether women exhibit mode-specific differences in EF. Furthermore, few studies have examined the influence of EF on the bilateral deficit (BD). PURPOSE The purpose of the present study was to examine the patterns of responses for normalized isokinetic peak torque and the BD during fatiguing, maximal, isokinetic UL and BL leg extensions in women. METHODS Ten women (Mean ± SD; age = 20.9 ± 2.08 years; height = 170.4 ± 6.5 cm; body mass = 63.0 ± 7.1 kg) performed 50 UL and BL maximal, concentric, isokinetic leg extensions at 180°·s-1 on three separate visits. Each visit was characterized by a fatiguing task of 50 repetitions with either the dominant limb (DL), non-dominant limb (NL), or both limbs (BL) in random order. Isokinetic peak torque values were averaged across 5 consecutive repetitions and normalized to the value at repetition 5 for the respective fatiguing task. A bilateral deficit index (BDI) was quantified as: BDI = [100 × BL/ (NL + DL)] - 100 with the absolute isokinetic peak torque values throughout the 50 repetitions. The mean differences for the normalized isokinetic peak torque values were examined with a 3 (Condition [BL, DL, NL]) × 10 (Repetition [5-50]) repeated measures (RM) ANOVA. The mean changes across repetitions for the BDI were examined with a 1 × 10 (Repetition [5-50]) RM ANOVA. RESULTS The 3 × 10 RM ANOVA demonstrated a significant (p < 0.01, η2p = 0.21) interaction with post-hoc analyses indicating an earlier decline in normalized peak torque for the DL (repetition 30) and NL (repetition 25) conditions than the BL (repetition 50) condition. The 1 × 10 RM ANOVA demonstrated no significant mean changes for the BDI (p = 0.05, η2p = 0.29). CONCLUSION These results indicated that the women exhibited a greater EF during UL compared to BL fatiguing, maximal, isokinetic leg extensions. While all participants exhibited a BD, there were no significant changes in the BD across the fatiguing task. Future studies are warranted to compare the mechanisms of task-specific EF between women and men.