Like any other kind of cell, muscle cells produce energy by oxidizing the fuel substrate that they absorb together with the needed oxygen from the surroundings. Oxidation occurs entirely within the cell. It means that the reactants and products of reaction must at some time be dissolved in the cell’s cytosol. If a cell operates at steady state, its cytosol composition remains constant. Therefore, the cytosol in a muscle that produces work at steady state must contain a constant amount of fuel, oxygen, and product of reaction dissolved in it. The greater the power produced, the higher the concentration of these solutes. There is a limit, however, to the maximum amount of solutes that the cytosol can contain without damaging the cell. General thermodynamic arguments, which are reviewed in this paper, help relate this limit to the dehydration and overhydration limits of the cell. The present analysis shows that the same limits entail a limit to the maximum power that a muscle can produce at steady state. This limit depends on the composition of the fuel mixture used by the muscle. The analysis also determines the number of fuel carbon atoms that must be oxidized in parallel within a cell to produce a given power. It may well happen that a muscle cannot reach the maximum attainable power because it cannot activate all the parallel oxidation paths that are needed to produce it. This may be due to a series of reasons ranging from health issues to a lack of training. The paper shows how the methods of indirect calorimetry can provide all the experimental data needed to determine the actual number of parallel oxidation paths that at steady state must be active in a muscle in a given exercise. A diagram relating muscle power to the number of parallel oxidation paths and fuel composition is finally presented. It provides a means to assess the power capacity of animal muscles and can be applied to evaluate their fitness, stamina, margins for improvement, and athletic potential.

中文翻译：

---

限制骨骼肌的稳态有氧能力

像任何其他类型的细胞一样，肌肉细胞通过氧化它们从环境中吸收的燃料底物以及所需的氧气来产生能量。氧化完全发生在细胞内。这意味着反应物和反应产物必须在某个时间溶解在细胞的细胞质中。如果细胞在稳定状态下运行，其细胞质组成保持不变。因此，在稳定状态下产生功的肌肉中的细胞质必须含有恒定量的燃料、氧气和溶解在其中的反应产物。产生的功率越大，这些溶质的浓度就越高。然而，在不损害细胞的情况下，细胞溶质可以包含的最大溶质量是有限的。本文综述的一般热力学论证，帮助将此限制与细胞的脱水和过度水化限制联系起来。目前的分析表明，相同的限制需要限制肌肉在稳定状态下可以产生的最大功率。这个限制取决于肌肉使用的燃料混合物的成分。该分析还确定了必须在电池内并行氧化以产生给定功率的燃料碳原子数。很可能肌肉无法达到最大可达到的力量，因为它无法激活产生它所需的所有平行氧化路径。这可能是由于一系列原因造成的，从健康问题到缺乏培训。该论文展示了间接量热法如何提供所需的所有实验数据，以确定在给定运动中肌肉在稳态时必须活跃的平行氧化路径的实际数量。最后呈现了将肌肉力量与平行氧化路径的数量和燃料成分相关联的图表。它提供了一种评估动物肌肉力量能力的方法，可用于评估它们的健康、耐力、改进空间和运动潜力。