Grant S M, Green H J, Phillips S M, Sutton J R
Department of Kinesiology, University of Waterloo, Ontario, Canada.
Eur J Appl Physiol Occup Physiol. 1997;76(4):356-62. doi: 10.1007/s004210050261.
To investigate the hypothesis that an increase in plasma volume (PV) is obligatory in reducing the cardiovascular drift that is associated with prolonged exercise following training, a plasma expander (Macrodex) was used to acutely elevate PV. Eight untrained volunteers [maximal oxygen consumption; VO2max 45.2 (2.2) ml x kg(-1) x min(-1), mean (SE)] cycled for 2 h [at 46 (4)% VO2max] in ambient conditions either with no PV expansion (CON) or following PV expansions of either 14% (LOW) or 21% (HIGH). During CON, heart rate (HR) increased (P < 0.05) from 147 (2.4) beats x min(-1) to 173 (3.6) beats x min(-1) from 15 to 120 min of exercise. Both LOW and HIGH conditions depressed (P < 0.05) HR, an effect that was manifested following 15 min of exercise. In contrast, stroke volume (SV) was elevated following PV expansion, with values (ml) of 89.6 (6.8), 97.8 (5.9) and 104 (4.6) noted by 15 min of exercise for CON, LOW and HIGH conditions, respectively. Acute PV expansion, regardless of magnitude, also resulted in elevations in cardiac output (Qc). These differences between conditions persisted throughout the exercise, as did the elevation in Qc that was noted with LOW and HIGH conditions. No difference between Qc, HR or SV was found between LOW and HIGH. In addition, neither LOW nor HIGH conditions altered the change in rectal temperature that was observed during exercise. These results demonstrate that, at least for moderate exercise performed in ambient conditions, PV expansion serves only to alter cardiac function (Qc, HR, SV) early in exercise, and not to attenuate the drift that occurs as the exercise is prolonged.
为了研究如下假设，即训练后进行长时间运动时，血浆量（PV）增加对于减少心血管漂移是必不可少的，使用了一种血浆扩容剂（右旋糖酐）来急性升高PV。八名未经训练的志愿者[最大耗氧量；VO2max为45.2（2.2）ml·kg⁻¹·min⁻¹，均值（标准误）]在环境条件下进行2小时的骑行[以46（4）%VO2max的强度]，分为不进行PV扩容（CON）组，以及PV分别扩容14%（LOW）或21%（HIGH）组。在CON组中，运动15至120分钟期间，心率（HR）从147（2.4）次/分钟增加到173（3.6）次/分钟（P<0.05）。LOW组和HIGH组均使HR降低（P<0.05），该效应在运动15分钟后显现。相反，PV扩容后每搏输出量（SV）升高，运动15分钟时，CON组、LOW组和HIGH组的SV值（ml）分别为89.6（6.8）、97.8（5.9）和104（4.6）。急性PV扩容，无论幅度大小，也导致心输出量（Qc）升高。不同条件之间的这些差异在整个运动过程中持续存在，LOW组和HIGH组中观察到的Qc升高情况也是如此。LOW组和HIGH组之间在Qc、HR或SV方面未发现差异。此外，LOW组和HIGH组均未改变运动期间观察到的直肠温度变化。这些结果表明，至少对于在环境条件下进行的中等强度运动，PV扩容仅在运动早期改变心脏功能（Qc、HR、SV），而不会减弱运动持续进行时发生的漂移。
