Twitch Properties, But Not Aerobic Fitness Are Related To Electrically Stimulated Critical Torque

Previous research has demonstrated a relationship between maximal strength and fatigue characteristics during exercise. Additionally, maximal strength has been shown to correlate to work performed above critical torque. Fiber type has also been shown to be predictive of critical power, but little is known about its relationship to critical torque. PURPOSE: The purpose of the present study was to examine relationships among aerobic training status, muscle twitch properties, fatigue rate, and critical toruqe during electrically stimulated exercise. METHODS: Twenty individuals participated, 10 were aerobically trained and 10 were sedentary. A VO2 peak test was performed on a cycle ergometer. Participants then performed an electrically stimulated critical torque test at a starting torque of 25% of their maximum voluntary contraction. Stimulation frequency was set at 100 Hz and contractions occurred at a duty cycle of 2:2. In addition to critical torque, dependent measures included the initial rate of fatigue (the slope of decline over the initial 10 contractions), rate of force development and rate of force relaxation. Independent t-tests were used to compare outcome measures between trained and untrained groups and Pearson correlation coefficients were calculated to examine relationships among dependent measures. RESULTS: The trained and sedentary group differed in VO2 peak (54.3 ± 6.2 vs. 35.7 ± 4.6 ml·kg-1·min-1; p < 0.001). No differences were found in stimulated critical torque (36.5 ± 11.1 vs. 33.6 ± 12.2% of starting torque; p = 0.58), slope of torque decline (0.48 ± 0.23 vs 0.46 ± 0.24; p = 0.90), rate of force development (275 ± 137 vs 250 ± 65 Nm·s-1; p = 0.63) and rate of force relaxation (179 ± 86 vs 173 ± 44 Nm·s-1) between groups. A significant relationship was found between starting torque and critical torque (r = -0.66; p < 0.05), rate of torque of development and critical torque (r = -0.42; p < 0.05) and rate of torque relaxation and critical torque (r = -0.66; p < 0.05). Additionally, the slope of torque decline was also correlated with starting torque (r = 0.77; p < 0.05) and critical torque (r = -0.86; p < 0.05). CONCLUSIONS: Our findings indicate aerobic training status does not affect critical torque or the initial rate of peripheral fatigue during stimulated exercise.