Broxterman Ryan M, Layec Gwenael, Hureau Thomas J, Morgan David E, Bledsoe Amber D, Jessop Jacob E, Amann Markus, Richardson Russell S
1Geriatric Research, Education, and Clinical Center, Salt Lake City Veteran's Affairs Medical Center, Salt Lake City, UT; 2Department of Internal Medicine, University of Utah, Salt Lake City, UT; 3Department of Anesthesiology, University of Utah, Salt Lake City, UT; and 4Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT.
Med Sci Sports Exerc. 2017 Dec;49(12):2404-2413. doi: 10.1249/MSS.0000000000001391.
The purpose of this study was to investigate the role of the group III/IV muscle afferents in the bioenergetics of exercising skeletal muscle beyond constraining the magnitude of metabolic perturbation.
Eight healthy men performed intermittent isometric knee-extensor exercise to task failure at ~58% maximal voluntary contraction under control conditions (CTRL) and with lumbar intrathecal fentanyl to attenuate group III/IV leg muscle afferents (FENT). Intramuscular concentrations of phosphocreatine (PCr), inorganic phosphate (Pi), diprotonated phosphate (H2PO4), adenosine triphosphate (ATP), and pH were determined using phosphorous magnetic resonance spectroscopy (P-MRS).
The magnitude of metabolic perturbation was significantly greater in FENT compared with CTRL for [Pi] (37.8 ± 16.8 vs 28.6 ± 8.6 mM), [H2PO4] (24.3 ± 12.2 vs 17.9 ± 7.1 mM), and [ATP] (75.8% ± 17.5% vs 81.9% ± 15.8% of baseline), whereas there was no significant difference in [PCr] (4.5 ± 2.4 vs 4.4 ± 2.3 mM) or pH (6.51 ± 0.10 vs 6.54 ± 0.14). The rate of perturbation in [PCr], [Pi], [H2PO4], and pH was significantly faster in FENT compared with CTRL. Oxidative ATP synthesis was not significantly different between conditions. However, anaerobic ATP synthesis, through augmented creatine kinase and glycolysis reactions, was significantly greater in FENT than in CTRL, resulting in a significantly greater ATP cost of contraction (0.049 ± 0.016 vs 0.038 ± 0.010 mM·min·N).
Group III/IV muscle afferents not only constrain the magnitude of perturbation in intramuscular Pi, H2PO4, and ATP during small muscle mass exercise but also seem to play a role in maintaining efficient skeletal muscle contractile function in men.
本研究旨在探究Ⅲ/Ⅳ类肌传入神经在骨骼肌运动生物能量学中的作用，不仅仅局限于限制代谢紊乱的程度。
8名健康男性在对照条件下（CTRL）以及使用腰椎鞘内注射芬太尼以减弱Ⅲ/Ⅳ类腿部肌肉传入神经（FENT）的情况下，进行间歇性等长伸膝运动直至任务失败，运动强度约为最大自主收缩的58%。使用磷磁共振波谱法（P-MRS）测定肌内磷酸肌酸（PCr）、无机磷酸盐（Pi）、二质子化磷酸盐（H2PO4）、三磷酸腺苷（ATP）的浓度以及pH值。
与CTRL相比，FENT组中[Pi]（37.8±16.8对28.6±8.6 mM）、[H2PO4]（24.3±12.2对17.9±7.1 mM）和[ATP]（占基线的75.8%±17.5%对81.9%±15.8%）的代谢紊乱程度显著更大，而[PCr]（4.5±2.4对4.4±2.3 mM）或pH（6.51±0.10对6.54±0.14）无显著差异。与CTRL相比,FENT组中[PCr]、[Pi]、[H2PO4]和pH的紊乱速率明显更快。不同条件下氧化ATP合成无显著差异。然而，通过增强肌酸激酶和糖酵解反应，FENT组的无氧ATP合成显著高于CTRL组，导致收缩的ATP成本显著更高（0.049±0.016对0.038±0.010 mM·min·N）。
Ⅲ/Ⅳ类肌传入神经不仅在小肌肉量运动期间限制肌内Pi、H2PO4和ATP的紊乱程度，而且似乎在维持男性骨骼肌有效收缩功能中发挥作用。
