Performance and perceived fatigability across the intensity spectrum: Role of muscle mass during cycling.

INTRODUCTION: The role of muscle mass in modulating performance and perceived fatigability across the entire intensity spectrum during cycling remains unexplored. We hypothesized that at task failure (T lim ), muscle contractile function would decline more following single- (SL) vs. double-leg (DL) cycling within severe- and extreme-, but not moderate- and heavy-, intensities.

METHODS: Following DL and SL ramp-incremental tests, on separate days, eleven recreationally active males (V̇O2max : 49.5±7.7mL·kg-1 ·min-1 ) completed SL and DL cycling until T lim within each intensity domain. Power output for SL trials was set at 60% of the corresponding DL trial. Prior to and immediately after T lim , participants performed an isometric maximal voluntary contraction (MVC) coupled with one superimposed and three resting femoral nerve stimulations (100Hz; 10Hz; single twitch ( Q tw )) to measure performance fatigability. Perceived fatigue, leg pain, dyspnea, and effort were collected during trials.

RESULTS: T lim within each intensity domain was not different between SL and DL (all P>0.05 ). MVC declined more for SL vs. DL following heavy- (-42±16% vs. -30±18%; P=0.011 ) and severe-intensity cycling (-41±12% vs. -31±15%; P=0.036 ). Similarly, peak Q tw force declined more for SL following heavy- (-31±12% vs. -22±10%; P=0.007 ) and severe-intensity cycling (-49±13% vs. -40±7%; P=0.048 ). Except for heavy-intensity, voluntary activation reductions were similar between modes. Similarly, except for dyspnea, which was lower for SL vs. DL across all domains, ratings of fatigue, pain, and effort were similar at T lim between exercise modes.

CONCLUSIONS: Thus, the amount of muscle mass modulates the extent of contractile function impairment in an intensity-dependant manner.