Author(s): ABOODARDA, J., ABOODARDA, S.J., ZHANG, J., MACINNIS, M.J., IANNETTA, D. , Institution: UNIVERSITY OF CALGARY, Country: CANADA, Abstract-ID: 1429

INTRODUCTION:
The extent of performance and perceived fatigability varies based on the volume of exercised muscle mass (1,2). However, no study to date has explored this effect across the entire intensity spectrum. Accordingly, this study aims to investigate alterations in muscle contractile function, central voluntary activation and perceived responses to single-leg (SL) and double-leg (DL) cycling tasks performed within four intensity domains.
METHODS:
Eleven males (29±4 years) performed SL and DL cycling to task failure in the moderate (MOD), heavy (HVY), severe (SVR), and extreme (EXT) intensity domains, as characterized by gas exchange threshold, respiratory compensation point, and maximal aerobic capacity from a DL ramp incremental test. SL cycling was performed at 60% of the power output corresponding to DL trials. Voluntary and evoked contractions, including 5s MVC of the dominant knee extensors combined with superimposed 100 Hz doublets (Db100) and resting Db100, 10 Hz doublets (Db10), and single twitch electrical stimuli of the femoral nerve were performed at baseline, immediately upon task failure, and following 1, 4, and 8 min of recovery. Perceived fatigue, leg pain, dyspnea, and effort were collected during trials. Two-way repeated measures ANOVAs with Bonferroni post hoc examined 2 modes × 4 timepoints within each domain.
RESULTS:
Time to task failure was similar between SL and DL cycling in all domains. MVC declined more following SL in SVR (SL vs. DL: -41±12% vs. -31±15%; P=0.036) and HVY domains (-42±16% vs. -30±18%; P=0.011). Also, peak twitch force declined more following SL at SVR (-49±13% vs. -40±7%; P=0.048) and HVY domains (-31±12% vs. -22±10%; P=0.007). Voluntary activation declined more following SL than DL at HVY (-20±15% vs. -9±10%; P=0.008). Dyspnea was greater following DL at HVY (7±3 vs. 6±3; P=0.031), SVR (8±2 vs. 6±2; P=0.001), and EXT domains (7±2 vs. 5±2; P=0.025), whereas ratings of fatigue, pain, and effort were similar between exercise modes.
CONCLUSION:
These findings suggest that metabolic perturbations within smaller muscle mass exercise (e.g., SL vs. DL cycling) can result in greater impairments in muscle contractile function within the SVR and HVY domains. However, the impairment in muscle function may be exacerbated for DL cycling within the MOD domain. Also, except for greater dyspnea, perceived responses between exercised muscle masses did not show any difference between domains. Collectively, these findings indicate that the modulatory effect of muscle mass on the extent of performance and perceived fatigability is exercise intensity-dependent.
1. Rossman et al., 2012, Acta Physiol
2. Zhang et al., 2021, AJP-Regul Integr Comp Physiol