Broxterman Ryan M, Layec Gwenael, Hureau Thomas J, Amann Markus, Richardson Russell S
Geriatric Research, Education, and Clinical Center, Salt Lake City Department of Veterans Affairs Medical Center, Salt Lake City, Utah;
Department of Internal Medicine, University of Utah, Salt Lake City, Utah.
J Appl Physiol (1985). 2017 May 1;122(5):1208-1217. doi: 10.1152/japplphysiol.01093.2016. Epub 2017 Feb 16.
Although all-out exercise protocols are commonly used, the physiological mechanisms underlying all-out exercise performance are still unclear, and an in-depth assessment of skeletal muscle bioenergetics is lacking. Therefore, phosphorus magnetic resonance spectroscopy (P-MRS) was utilized to assess skeletal muscle bioenergetics during a 5-min all-out intermittent isometric knee-extensor protocol in eight healthy men. Metabolic perturbation, adenosine triphosphate (ATP) synthesis rates, ATP cost of contraction, and mitochondrial capacity were determined from intramuscular concentrations of phosphocreatine (PCr), inorganic phosphate (P), diprotonated phosphate ([Formula: see text]), and pH. Peripheral fatigue was determined by exercise-induced alterations in potentiated quadriceps twitch force (Q) evoked by supramaximal electrical femoral nerve stimulation. The oxidative ATP synthesis rate (ATP) attained and then maintained peak values throughout the protocol, despite an ~63% decrease in quadriceps maximal force production. ThusATP normalized to force production (ATP gain) significantly increased throughout the exercise (1st min: 0.02 ± 0.01, 5th min: 0.04 ± 0.01 mM·min·N), as did the ATP cost of contraction (1st min: 0.048 ± 0.019, 5th min: 0.052 ± 0.015 mM·min·N). Additionally, the pre- to postexercise change in Q (-52 ± 26%) was significantly correlated with the exercise-induced change in intramuscular pH ( = 0.75) and [Formula: see text] concentration ( = 0.77). In conclusion, the all-out exercise protocol utilized in the present study elicited a "slow component-like" increase in intramuscular ATP gain as well as a progressive increase in the phosphate cost of contraction. Furthermore, the development of peripheral fatigue was closely related to the perturbation of specific fatigue-inducing intramuscular factors (i.e., pH and [Formula: see text] concentration). The physiological mechanisms and skeletal muscle bioenergetics underlying all-out exercise performance are unclear. This study revealed an increase in oxidative ATP synthesis rate gain and the ATP cost of contraction during all-out exercise. Furthermore, peripheral fatigue was related to the perturbation in pH and deprotonated phosphate ion. These findings support the concept that the oxygen uptake slow component arises from within active skeletal muscle and that skeletal muscle force generating capacity is linked to the intramuscular metabolic milieu.
尽管全力运动方案被广泛使用，但全力运动表现背后的生理机制仍不清楚，且缺乏对骨骼肌生物能量学的深入评估。因此，本研究利用磷磁共振波谱（P-MRS）对8名健康男性在5分钟全力间歇性等长伸膝运动方案中的骨骼肌生物能量学进行评估。通过肌肉内磷酸肌酸（PCr）、无机磷酸盐（P）、双质子化磷酸盐（[公式：见原文]）和pH值的浓度来确定代谢扰动、三磷酸腺苷（ATP）合成速率、收缩的ATP消耗和线粒体容量。通过运动诱导的股神经超强电刺激诱发的股四头肌增强抽搐力（Q）的变化来确定外周疲劳。尽管股四头肌最大力量产生下降了约63%，但在整个运动方案中，氧化ATP合成速率（ATP）达到并维持了峰值。因此，归一化到力量产生的ATP（ATP增益）在整个运动过程中显著增加（第1分钟：0.02±0.01，第5分钟：0.04±0.01 mM·min·N），收缩的ATP消耗也显著增加（第1分钟：0.048±0.019，第5分钟：0.052±0.015 mM·min·N）。此外，运动前后Q的变化（-52±26%）与运动诱导的肌肉内pH值变化（=0.75）和[公式：见原文]浓度变化（=0.77）显著相关。总之，本研究中使用的全力运动方案引发了肌肉内ATP增益的“慢成分样”增加以及收缩的磷酸盐消耗的逐渐增加。此外，外周疲劳的发展与特定疲劳诱导肌肉内因素（即pH值和[公式：见原文]浓度）的扰动密切相关。全力运动表现背后的生理机制和骨骼肌生物能量学尚不清楚。本研究揭示了全力运动期间氧化ATP合成速率增益和收缩的ATP消耗增加。此外，外周疲劳与pH值和去质子化磷酸盐离子的扰动有关。这些发现支持了摄氧慢成分源于活跃骨骼肌内部以及骨骼肌力量产生能力与肌肉内代谢环境相关的概念。
