Russ David W, Lanza Ian R, Rothman Douglas, Kent-Braun Jane A
Department of Exercise Science, Totman 108, University of Massachusetts, Amherst, 01035, USA.
Muscle Nerve. 2005 Nov;32(5):647-55. doi: 10.1002/mus.20396.
We have previously observed less muscle fatigue in women than men under conditions of intact circulation, but similar fatigue across the sexes during local ischemia. Thus, we hypothesized that women utilize their aerobic metabolic pathways to a greater extent than do men. To test this hypothesis, we examined the extent to which different pathways of intramuscular adenosine triphosphate (ATP) production were utilized by men and women during maximal voluntary isometric contractions. Force production during 15-s and 60-s contractions were recorded in parallel sessions. In one session, central activation was assessed with electrical stimulation. In the other, phosphorus magnetic resonance spectroscopy was used to quantify muscle oxidative capacity, and the contributions of glycolysis and oxidative phosphorylation to ATP synthesis during the 60-s contraction. Fatigue and central activation were similar in men and women during both the 15-s and 60-s contractions. The rate constants of phosphocreatine recovery following the 15-s contraction were similar in men and women, indicating similar oxidative capacities. Men exhibited greater acidosis and peak glycolytic rates compared with women during the 60-s contraction, with no differences observed in creatine kinase flux or the percent of oxidative capacity utilized. We conclude that men exhibit greater in vivo glycolysis during brief, intense isometric contractions. Although this metabolic difference did not contribute to any observable differences in fatigue in the present study, these results highlight a potentially important mechanism to explain sex-related differences in muscle function.
我们之前观察到，在循环系统完整的情况下，女性比男性的肌肉疲劳程度更低，但在局部缺血期间，两性的疲劳程度相似。因此，我们推测女性比男性更多地利用其有氧代谢途径。为了验证这一假设，我们研究了在最大自主等长收缩过程中，男性和女性利用肌肉内三磷酸腺苷（ATP）产生的不同途径的程度。在平行的实验环节中记录了15秒和60秒收缩过程中的力量产生情况。在一个实验环节中，通过电刺激评估中枢激活情况。在另一个实验环节中，利用磷磁共振波谱法量化肌肉氧化能力，以及在60秒收缩过程中糖酵解和氧化磷酸化对ATP合成的贡献。在15秒和60秒收缩过程中，男性和女性的疲劳程度和中枢激活情况相似。15秒收缩后磷酸肌酸恢复的速率常数在男性和女性中相似，表明氧化能力相似。在60秒收缩过程中，与女性相比，男性表现出更严重的酸中毒和更高的糖酵解峰值速率，而在肌酸激酶通量或氧化能力利用率方面未观察到差异。我们得出结论，在短暂、强烈的等长收缩过程中，男性体内的糖酵解程度更高。尽管这种代谢差异在本研究中并未导致疲劳方面的任何可观察到的差异，但这些结果突出了一个潜在的重要机制，可用于解释肌肉功能的性别相关差异。
