Influence of two pedalling rate conditions on mechanical output and physiological responses during all-out intermittent exercise

The purpose of this study was to investigate the effect of two cycling velocities on power output and concomitant metabolic and cardiorespiratory responses to repeated all-out exercises. Mean power output (P _m), total work (W _tot), total oxygen consumption (VO_2tot) and blood lactate accumulation (Δ[La]_b) were evaluated in 13 male subjects who performed two series of twelve 5-s bouts of sprint cycling. Recovery periods of 45-s were allowed between trials. One series was executed at optimal velocity (V _opt: velocity for greatest power) and the other one at 50% V _opt (0.5V _opt). Velocities obtained in these conditions were V_opt=116.6 (4.7) rpm; 0.5V_opt=60.6 (4.9) rpm. After a phase of adaptation in oxygen uptake in the first part of the series, the data from the 6th to the 12th sprint were as follows: P _m, 924.6 (73.9) versus 689.2 (61.8) W; W _tot, 29.95 (4.14) versus 22.04 (3.17) kJ; VO_2tot, 12.80 (1.36) versus 10.58 (1.37) l; Δ[La]_b, 2.72 (1.22) versus 0.64 (0.79) mmol.l⁻¹, respectively (P<0.001). Both W _tot and VO_2tot were consistently higher at optimal velocity (+21 and +35.8%, respectively). The present findings demonstrate that during intermittent short-term all-out exercise requiring maximal activation, the energy turnover is not necessarily maximal. It depends on muscle contraction velocity. The increase, lower than expected, in metabolic response from 0.5V _opt to V _opt suggests also that mechanical efficiency is higher at V _opt.