Barstow T J, Jones A M, Nguyen P H, Casaburi R
Department of Kinesiology, 8 Natatorium, Kansas State University, Manhattan, KS 66506-0302, USA.
Exp Physiol. 2000 Jan;85(1):109-16.
We recently reported that a higher percentage of type I fibres in vastus lateralis and a greater peak oxygen uptake (O2) were associated with a greater initial rise in O2 (O2 /W, where W is work rate) following the onset of heavy constant power output exercise (above the lactate threshold, LT). It was unclear if these results were true only for heavy exercise, or if the association between fibre type and/or fitness and O2 /W would also be seen for moderate (< LT) exercise. The purpose of the present study was to compare the relationships between fibre type or peak O2 and O2 /W determined for moderate (< LT) and heavy (> LT) exercise intensities during incremental exercise. Nine healthy subjects performed an incremental ramp test on a cycle ergometer. The O2 /Wslope was calculated for the domain of power outputs up to the LT (S1), from the LT towards peak O2 (S2), and over the entire linear portion of the O2 /W response (ST), and compared to fibre type distribution determined from biopsy of the vastus lateralis, and to peak O2 (as ml kg-1 min-1). Significant correlations between O2 /W and the proportion of type I fibres were found for each exercise domain (r is 0.69, 0.71 and 0.84 for S1, S2 and ST, respectively, P < 0.05). S1 ranged between about 9 ml min-1 W-1 for a low proportion of type I fibres and 11 ml min-1 W-1 for a high proportion of type I fibres. Similar correlations were also found between S2 (r = 0.70) and ST (r = 0.76) and peak O2. These results are consistent with our previous findings during > LT constant power output exercise, and suggest that the proportion of type I fibres, and possibly fitness as indicated by peak O2, is associated with greater O2 /W during the initial adjustment to < LT as well as > LT exercise. These results do not appear to be explained by classical descriptions of the kinetics of adjustment of O2 following the onset of ramp or constant power output exercise. They might reflect enhanced motor unit recruitment in subjects with a greater percentage of type I fibres, and/or who are more aerobically fit. However, the underlying mechanism for these findings must await further study.
我们最近报告称，股外侧肌中较高比例的I型纤维以及较高的峰值摄氧量（O₂）与重度恒定功率输出运动（高于乳酸阈，LT）开始后O₂的更大初始上升幅度（O₂ /W，其中W为工作率）相关。尚不清楚这些结果是否仅适用于重度运动，或者纤维类型和/或体能与O₂ /W之间的关联在中度（<LT）运动中是否也会出现。本研究的目的是比较在递增运动期间，针对中度（<LT）和重度（>LT）运动强度所确定的纤维类型或峰值O₂与O₂ /W之间的关系。九名健康受试者在自行车测力计上进行了递增斜坡测试。计算了直至LT的功率输出范围（S1）、从LT到峰值O₂的范围（S2）以及O₂ /W反应的整个线性部分（ST）的O₂ /W斜率，并将其与通过股外侧肌活检确定的纤维类型分布以及峰值O₂（以ml kg⁻¹ min⁻¹为单位）进行比较。在每个运动范围内均发现O₂ /W与I型纤维比例之间存在显著相关性（S1、S2和ST的r分别为0.69、0.71和0.84，P < 0.05）。对于低比例的I型纤维，S1约在9 ml min⁻¹ W⁻¹至11 ml min⁻¹ W⁻¹之间。在S2（r = 0.70）和ST（r = 0.76）与峰值O₂之间也发现了类似的相关性。这些结果与我们之前在>LT恒定功率输出运动期间的发现一致，表明I型纤维的比例以及可能由峰值O₂所指示的体能，在初始调整至<LT以及>LT运动期间与更大的O₂ /W相关。这些结果似乎无法用斜坡或恒定功率输出运动开始后O₂调整动力学的经典描述来解释。它们可能反映了I型纤维比例较高和/或有氧适应性更强的受试者中运动单位募集的增强。然而，这些发现的潜在机制尚有待进一步研究。
