Endo Masako, Okada Yoko, Rossiter Harry B, Ooue Anna, Miura Akira, Koga Shunsaku, Fukuba Yoshiyuki
Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, 1-1-71, Ujina-higashi, Minami-ku, Hiroshima, 734-8558, Japan.
Eur J Appl Physiol. 2005 Dec;95(5-6):418-30. doi: 10.1007/s00421-005-0051-2. Epub 2005 Sep 29.
The mechanism that alters the pulmonary VO2 response to heavy-intensity exercise following prior heavy exercise has been frequently ascribed to an improvement in pre-exercise blood flow (BF) or O(2) delivery. Interventions to improve O(2) delivery have rarely resulted in a similar enhancement of VO2. However, the actual limb blood flow and VO2 dynamics in the second bout of repeated exercise remain equivocal. Seven healthy female subjects (21-32 years) performed consecutive 6-min (separated by 6 min of 10 W exercise) bilateral knee extension (KE) exercise in a semisupine position at a work rate halfway between the lactate threshold (LT) and VO2peak. Femoral artery blood flow (FBF) was measured by Doppler ultrasound simultaneously with breath-by-breath VO2 each protocol being repeated at least four times for precise kinetic characterization. The effective time-constant (tau') of the VO2 response was reduced following prior exercise (bout 1: 61.0 +/-10.5 vs. bout 2: 51.6+/-9.0 s; mean +/- SD; P<0.05), which was a result of a reduced slow component (bout 1: 16.0+/-8.0 vs. bout 2: 12.5+/-6.7 %; P<0.05) and an unchanged 'primary' tau. FBF was consistently faster than VO2. However, there was no bout-effect on tau' FBF (bout 1: 28.2+/-12.0 vs. bout 2: 34.2+/-8.5 s). The relationship between the exercise-associated VO2 (i.e., deltaVO2) and Delta FBF was similar between bouts, with a tendency (N.S: P>0.05) for deltaVO2/deltaFBF to be increased during the transition to bout 2 rather than decreased, as hypothesized. The return of VO2 kinetics toward first order, therefore, was associated with an 'appropriate', not enhanced, BF to the working muscles. Whether a relative prior-hyperemia in bout 2 enables a more homogeneous intramuscular distribution of BF and/or metabolic response is unclear, however, these data are consistent with events more proximal to the exercise muscle in mediating the VO2 response during repeated heavy-intensity KE exercise.
先前进行大强度运动后，改变肺部对大强度运动的VO₂反应的机制常被归因于运动前血流量（BF）或O₂输送的改善。改善O₂输送的干预措施很少能使VO₂有类似程度的增强。然而，重复运动第二回合中实际的肢体血流量和VO₂动态变化仍不明确。七名健康女性受试者（21 - 32岁）在半仰卧位进行连续两次6分钟（中间间隔6分钟10瓦运动）的双侧膝关节伸展（KE）运动，运动强度为乳酸阈值（LT）和VO₂峰值之间的一半。通过多普勒超声测量股动脉血流量（FBF），同时逐次呼吸测量VO₂，每个方案至少重复四次以进行精确的动力学特征分析。先前运动后VO₂反应的有效时间常数（tau'）降低（第一回合：61.0±10.5秒 vs. 第二回合：51.6±9.0秒；平均值±标准差；P<0.05），这是由于慢成分降低（第一回合：16.0±8.0% vs. 第二回合：12.5±6.7%；P<0.05）且“主要”tau不变。FBF始终比VO₂更快。然而，tau' FBF没有回合效应（第一回合：28.2±12.0秒 vs. 第二回合：34.2±8.5秒）。两回合之间运动相关VO₂（即deltaVO₂）与Delta FBF的关系相似，如假设的那样，在过渡到第二回合期间deltaVO₂/deltaFBF有增加的趋势（无显著性差异：P>0.05）而非降低。因此，VO₂动力学恢复到一级状态与向工作肌肉输送“适当”而非增强的BF有关。然而，第二回合中相对的先前充血是否能使BF在肌肉内更均匀地分布和/或代谢反应尚不清楚，不过，这些数据与在重复大强度KE运动期间介导VO₂反应时更接近运动肌肉的事件一致。
