抄録
We hypothesized that a freely pace 10,000 m running race would induce a smaller physiological strain (heart rate and oxygen uptake) compared with one performed at the same average speed but with an imposed constant pace. Furthermore, we analyzed their scaling properties with a wavelet transform algorithm computed log2(wavelet transform energy) vs. log2(scale) to get its slope α which is the scaling exponent which is a measure of the irregularity of a time series. HR was sampled beat-by-beat and VO2 breath-by-breath. The enforced constant pace run elicited significantly higher mean VO2 value (53 ± 4 vs. 48 ± 5 ml kg−1 min−1, P < 0.001), HR (169 ± 13 vs. 165 ± 14 bpm, P < 0.01), and blood lactate concentration (6.6 ± 0.9 vs. 7.5 ± 1 mm, P < 0.001), than the freely pace run. HR and VO2 signals showed a scaling behaviour which means that the signals have similar irregularity (a self similarity) whatever the scale of analysis, in both constant and free pace 10,000 m runs. The scaling exponent was not significantly different according the type of run (free vs. constant, P > 0.05) and the signal (HR vs. VO2, P > 0.05). The higher metabolic cost of constant vs. free pace run did not affect the self similarity of HR and VO2 in both constant and free-pace. HR signal only kept its scaling-behavior with distance run whatever the type of run (free or constant).The results suggest that the larger degree of pace variation in freely paced races may be an intentionally chosen strategy designed to minimize the physiological strain during severe exercise and to prevent premature termination of effort even if the variability of the heart rate and VO2 are comparable in enforced constant vs. freely pace run and if HR keeps the same variability until the arrival.
