Harms C A, Wetter T J, St Croix C M, Pegelow D F, Dempsey J A
John Rankin Laboratory of Pulmonary Medicine, Department Preventive Medicine, University of Wisconsin, Madison, Wisconsin 53705, USA.
J Appl Physiol (1985). 2000 Jul;89(1):131-8. doi: 10.1152/jappl.2000.89.1.131.
The normal respiratory muscle effort at maximal exercise requires a significant fraction of cardiac output and causes leg blood flow to fall. We questioned whether the high levels of respiratory muscle work experienced in heavy exercise would affect performance. Seven male cyclists [maximal O(2) consumption (VO(2)) 63 +/- 5 ml. kg(-1). min(-1)] each completed 11 randomized trials on a cycle ergometer at a workload requiring 90% maximal VO(2). Respiratory muscle work was either decreased (unloading), increased (loading), or unchanged (control). Time to exhaustion was increased with unloading in 76% of the trials by an average of 1.3 +/- 0.4 min or 14 +/- 5% and decreased with loading in 83% of the trials by an average of 1.0 +/- 0.6 min or 15 +/- 3% compared with control (P < 0.05). Respiratory muscle unloading during exercise reduced VO(2), caused hyperventilation, and reduced the rate of change in perceptions of respiratory and limb discomfort throughout the duration of exercise. These findings demonstrate that the work of breathing normally incurred during sustained, heavy-intensity exercise (90% VO(2)) has a significant influence on exercise performance. We speculate that this effect of the normal respiratory muscle load on performance in trained male cyclists is due to the associated reduction in leg blood flow, which enhances both the onset of leg fatigue and the intensity with which both leg and respiratory muscle efforts are perceived.
在最大运动强度时，正常的呼吸肌用力需要消耗相当一部分心输出量，并导致腿部血流减少。我们质疑在剧烈运动中所经历的高水平呼吸肌工作是否会影响运动表现。七名男性自行车运动员[最大摄氧量（VO₂）63±5 ml·kg⁻¹·min⁻¹]每人在自行车测力计上以需要90%最大VO₂的工作量完成了11次随机试验。呼吸肌工作要么减少（卸载）、增加（加载），要么保持不变（对照）。与对照相比，在76%的试验中，卸载时疲劳时间平均增加1.3±0.4分钟或14±5%，在83%的试验中，加载时疲劳时间平均减少1.0±0.6分钟或15±3%（P<0.05）。运动期间呼吸肌卸载降低了VO₂，导致过度通气，并在整个运动过程中降低了呼吸和肢体不适感觉的变化率。这些发现表明，在持续的高强度运动（90%VO₂）中正常发生的呼吸功对运动表现有显著影响。我们推测，正常呼吸肌负荷对训练有素的男性自行车运动员运动表现的这种影响是由于腿部血流的相应减少，这既增强了腿部疲劳的发生，也增强了对腿部和呼吸肌用力的感知强度。
