PURPOSE:Although it has been largely acknowledged that isometric neuromuscular electrostimulation (NMES) exercise induces larger muscle damage than voluntary contractions, the corresponding effects on muscle energetics remain to be determined. Voluntary exercise-induced muscle damage (EIMD) has been reported to have minor slight effects on muscle metabolic response to subsequent dynamic exercise, but the magnitude of muscle energetics alterations for NMES EIMD has never been documented. METHODS:³¹P magnetic resonance spectroscopy measurements were performed in 13 young healthy males during a standardized rest-exercise-recovery protocol before (D0) and 2 d (D2) and 4 d (D4) after NMES EIMD on knee extensor muscles. Changes in kinetics of phosphorylated metabolite concentrations (i.e., phosphocreatine [PCr], inorganic phosphate [Pi], and adenosine triphosphate [ATP]) and pH were assessed to investigate aerobic and anaerobic rates of ATP production and energy cost of contraction (Ec). RESULTS:Resting [Pi]/[PCr] ratio increased at D2 (+39%) and D4 (+29%), mainly owing to the increased [Pi] (+43% and +32%, respectively), whereas a significant decrease in resting pH was determined (-0.04 pH unit and -0.03 pH unit, respectively). PCr recovery rate decreased at D2 (-21%) and D4 (-23%) in conjunction with a significantly decreased total rate of ATP production at D4 (-18%) mainly owing to an altered aerobic ATP production (-19%). Paradoxically, Ec was decreased at D4 (-21%). CONCLUSION:Overall, NMES EIMD led to intramuscular acidosis in resting muscle and mitochondrial impairment in exercising muscle. Alterations of noncontractile processes and/or adaptive mechanisms to muscle damage might account for the decreased Ec during the dynamic exercise.

译文

目的:尽管已经广泛认可等距神经肌肉电刺激(NMES)运动比自发性收缩引起的肌肉损伤更大,但对肌肉能量的相应影响尚待确定。据报道,自愿运动诱发的肌肉损伤(EIMD)对随后进行的动态运动的肌肉代谢反应具有轻微的轻微影响,但尚未记录NMES EIMD的肌肉能量变化的程度。
方法:在标准化的静坐锻炼恢复方案之前(D0),NMES EIMD后2 d(D2)和4 d(D4)之前,对13名年轻的健康男性进行了13 P磁共振波谱测量。评估了磷酸化代谢物浓度(即磷酸肌酸[PCr],无机磷酸[Pi]和三磷酸腺苷[ATP])的动力学变化,以研究有氧和无氧的ATP产生速率和收缩能量成本(Ec)。
结果:在第2天(39%)和第4天(29%)的休息Pi / [PCr]比增加,主要是由于Pi分别增加(分别为43%和32%),而静止pH值显着下降测定(分别为-0.04 pH单位和-0.03 pH单位)。在D2(-21%)和D4(-23%)处PCr回收率下降,同时在D4(-18%)处的ATP产生总速率显着下降,这主要是由于有氧ATP产生的改变(-19%)。矛盾的是,Ec在D4处降低(-21%)。
结论:总体而言,NMES EIMD导致静息肌发生肌内酸中毒,并导致运动肌的线粒体损伤。非收缩过程和/或对肌肉损伤的适应性机制的改变可能是动态运动过程中Ec降低的原因。

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