Motor Efficiency and Deficiency EA 2991, Faculty of Sport Sciences, University of Montpellier I , 34090 Montpellier, France.
J Sports Sci Med. 2006 Jun 1;5(2):254-65. eCollection 2006.
The aim of the present study was to test the hypothesis that compared to upright posture, slower oxygen uptake (VO2) kinetics resulting from exercise at the same relative metabolic load in the supine posture will be associated with increased muscle de-oxygenation and greater myoelectrical activity. Nine subjects completed one 12-min heavy-intensity constant-load exercises in each of the supine and upright postures on an electronically braked cycle ergometer at a same gain in metabolism per unit increase in work intensity (10.8 ± 1.3 vs. 11.8 ± 1.1 mlO2·min(-1)·W(-1) in upright and supine, respectively) on separate days. Breath-by-breath VO2 kinetics were analyzed with a double exponential model to characterize the primary and slow component phases. Myoelectrical activity (RMS) of the vastus lateralis (VL), rectus femoris, and biceps femoris muscles was recorded at different epochs of the exercise. Oxygenation of the VL muscle was recorded continuously by near-infrared spectroscopy. In supine compared with upright cycling, the primary time constant of VO2 kinetics was significantly increased (32.7 ± 10.7 s vs. 23.5 ± 6.7 s, respectively) while the absolute magnitude of VO2 slow component was decreased (p < 0.05) but not the relative amplitude. VL de-oxygenation was higher (p < 0.05) in supine cycling throughout the exercising period whereas RMS values for all muscles did not change appreciably over time. Our findings suggest that lowered oxygen supply induced by supine heavy exercise, alters oxidative metabolism dynamics and increases muscle de-oxygenation. However, cycling supine did not increase markedly the rate of muscle fatigue. Key PointsHydrostatic pressure gradients in blood vessels oriented longitudinally in the body are lesser in supine than in upright posture.Lowered oxygen supply induced with supine exercise slows oxidative metabolism dynamics and increases muscle de-oxygenation during heavy exercise.Compared to upright, supine exercise did not increase markedly the rate of muscle fatigue at a same relative metabolic load.
本研究旨在验证一个假设，即在相同的相对代谢负荷下，与仰卧位相比，运动导致的较慢的氧气摄取（VO2）动力学将与肌肉去氧合增加和肌电活动增加相关。9 名受试者在电子制动自行车测力计上分别完成了一次 12 分钟的仰卧位和直立位高强度恒负荷运动，在单位工作强度增加时代谢率的增益相同（仰卧位和直立位分别为 10.8 ± 1.3 和 11.8 ± 1.1 mlO2·min(-1)·W(-1)），在不同的日子。使用双指数模型分析呼吸呼吸 VO2 动力学，以表征主要和缓慢成分阶段。股外侧肌（VL）、股直肌和股二头肌的肌电活动（RMS）在运动的不同时期记录。通过近红外光谱连续记录 VL 肌肉的氧合。与直立骑自行车相比，仰卧位自行车的 VO2 动力学的主要时间常数明显增加（32.7 ± 10.7 s 与 23.5 ± 6.7 s，分别），而 VO2 慢成分的绝对值降低（p < 0.05）但相对幅度不变。整个运动期间，仰卧位自行车的 VL 去氧合作用更高（p < 0.05），而所有肌肉的 RMS 值随时间的变化不大。我们的研究结果表明，仰卧位剧烈运动引起的氧气供应降低改变了氧化代谢动力学并增加了肌肉去氧合作用。然而，仰卧位自行车并没有显著增加肌肉疲劳的速度。关键点在身体纵向定向的血管中，静水压梯度在仰卧位比直立位小。仰卧位运动引起的氧气供应降低会在剧烈运动时减缓氧化代谢动力学并增加肌肉去氧合作用。与直立位相比，在相同的相对代谢负荷下，仰卧位运动不会显著增加肌肉疲劳的速度。
