Muscle fiber recruitment and the slow component of O-2 uptake: constant work rate vs. all-out sprint exercise

作者：Vanhatalo Anni; Poole David C; DiMenna Fred J; Bailey Stephen J; Jones Andrew M^*

来源：American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, 2011, 300(3): R700-R707.

DOI：10.1152/ajpregu.00761.2010

• oxygen uptake kinetics
• electromyogram
• all-out critical power test
• maximum oxygen uptake
• fatigue
• exercise tolerance

The slow component of pulmonary O-2 uptake ((V) over dotO(2)) during constant work rate (CWR) high-intensity exercise has been attributed to the progressive recruitment of (type II) muscle fibers. We tested the following hypotheses: 1) the (V) over dotO(2) slow component gain would be greater in a 3-min all-out cycle test than in a work-matched CWR test, and 2) the all-out test would be associated with a progressive decline, and the CWR test with a progressive increase, in muscle activation, as estimated from the electromyogram (EMG) of the vastus lateralis muscle. Eight men (aged 21-39 yr) completed a ramp incremental test, a 3-min all-out test, and a work-and time-matched CWR test to exhaustion. The maximum (V) over dotO(2) attained in an initial ramp incremental test (3.97 +/- 0.83 l/min) was reached in both experimental tests (3.99 +/- 0.84 and 4.03 +/- 0.76 l/min for all-out and CWR, respectively). The (V) over dotO(2) slow component was greater (P < 0.05) in the all-out test (1.21 +/- 0.31 l/min, 4.2 +/- 2.2 ml . min(-1) . W-1) than in the CWR test (0.59 +/- 0.22 l/min, 1.70 +/- 0.5 ml . min(-1) . W-1). The integrated EMG declined by 26% (P < 0.001) during the all-out test and increased by 60% (P < 0.05) during the CWR test from the first 30 s to the last 30 s of exercise. The considerable reduction in muscle efficiency in the all-out test in the face of a progressively falling integrated EMG indicates that progressive fiber recruitment is not requisite for development of the (V) over dotO(2) slow component during voluntary exercise in humans.

• 出版日期2011-3