EFFECT OF PRIOR EXERCISE AT DIFFERENT PEDALING FREQUENCIES ON MAXIMAL POWER IN HUMANS

The effect of prior submaximal exercise performed at two different pedalling frequencies, 60 and 120 rev.min-1, on maximal short-term power output (STPO) was investigated in seven male subjects during cycling exercise on an isokinetic cycle ergometer. Exercise of 6-min duration at a power output equivalent to 92 (SD 5)% maximal oxygen uptake (VO2max), whether performed at a pedalling frequency of 60 or 120 rev.min-1, reduced maximal STPO generated at 120 rev.min-1 to a much greater extent than maximal STPO at 60 rev.min-1. After 6-min submaximal exercise at 60 rev.min-1 mean reductions in maximal STPO measured at 120 and 60 rev.min-1 were 27 (SD 11)% and 15 (SD 9)% respectively, and were not significantly different from the reductions after exercise at 120 rev.min-1, 20 (SD 13)% and 5 (SD 9)%, respectively. In addition, we measured the effect of prior exercise performed at the same absolute external mechanical power output [236 (SD 30)W] with pedalling frequencies of 60 and 120 rev.min-1. Although the external power output was the same, the leg forces required (absolute as well as expressed as a proportion of the maximal leg force available at the same velocity) were much higher in prior exercise performed at 60 rev.min-1. Nevertheless, maximal STPO generated at 120 rev.min-1 was reduced after exercise at 120 rev.min-1 [20 (SD 13)%, P<0.05] whereas no significant reduction in maximal STPO was found after prior exercise at 60 rev.min-1. The present findings would suggest that exercise performed at 92 (SD 5)% VO2max, whether at 60 or at 120 rev.min-1, selectively fatigues the faster fatigue-sensitive fibres resulting in a greater reduction in maximal STPO generated at 120 compared to 60 rev.min-1. The greater fatigue of maximal STPO generated at 120 rev.min-1 due to exercise performed at a power output of 236 (SD 30)W at 120 rev.min-1 compared to 60 rev.min-1 would suggest a relatively greater contribution of fast fatigue-sensitive fibres when higher movement frequencies and hence different muscle shortening velocities are used at this submaximal exercise intensity.