Effect of warm-up on VO2 kinetics during heavy exercise
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Warm-up (WU) is considered an essential part of exercise training in athletic, preventative and rehabilitative exercise programs. Exactly how WU augments exercise performance is unclear. Previous studies during free range exercise have shown down-regulation of power output (PO) and slower oxygen uptake (VO2) kinetics in the absence of WU. However, since PO early during an exercise bout is known to drive VO2 kinetics, it is unclear whether these results are primary or responsive to the lower PO in the absence of WU. Eight healthy, physically active volunteers (23.1 + 2.1 years) performed two 3 km time trials (TT), the first with WU to define mean PO (279 + 84 watts), the second without WU, and two square wave (SW) exercise tests to fatigue at a PO equal to the mean achieved on the TT with WU; one was performed with no WU and the other followed a 15 min WU protocol. Repeated measures ANOVA was used to analyze performance time, VO2 kinetics as measured by Mean Response Time (MRT), peak power output (PPO), % PPO, heart rate (HR) response, ventilation, and rating of perceived exertion. Following WU, performance time in the SW tests was not significantly greater (371.3 + 165.7 s vs. 338.3 + 155.1 s), maximal VO2 was significantly greater (4.2 + 1.1 vs. 3.9 + 0.9 L/min), HR was significantly greater (178 + 9 vs. 171 + 10 bpm), but MRT was not different (48.0 + 13.6 s vs. 45.1 + 7.9 s). Thus, the improved performance and overall aerobic response to exercise following WU could not be attributed to differences in MRT. These results fail to support the hypothesis that acceleration of VO2 kinetics, independent of differences in muscle PO, is an outcome of WU. These results suggest that the down-regulation of PO previously observed in studies of WU were responsible for the slower VO2 kinetics.
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Oxygen -- Physiological transport