Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.
Sport Medicine Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.
J Appl Physiol (1985). 2024 Jul 1;137(1):10-22. doi: 10.1152/japplphysiol.00120.2024. Epub 2024 May 23.
Critical power (CP) represents an important threshold for exercise performance and fatiguability. We sought to determine the extent to which sex, hemoglobin mass (Hb), and skeletal muscle characteristics influence CP. Before CP determination (i.e., 3-5 constant work rate trials to task failure), Hb and skeletal muscle oxidative capacity (τ) were measured and vastus lateralis (VL) muscle biopsy samples were collected from 12 females and 12 males matched for aerobic fitness relative to fat-free mass (FFM) [means (SD); V̇o: 59.2 (7.7) vs. 59.5 (7.1) mL·kg·FFM·min, respectively]. Males had a significantly greater CP than females in absolute units [225 (28) vs. 170 (43) W; = 0.001] but not relative to body mass [3.0 (0.6) vs. 2.7 (0.6) W·kg·BM; = 0.267] or FFM [3.6 (0.7) vs. 3.7 (0.8) W·kg·FFM; = 0.622]. Males had significantly greater ' ( ≤ 0.030) and greater Hb ( ≤ 0.016) than females, regardless of the normalization approach; however, there were no differences in mitochondrial protein content ( = 0.375), τ ( = 0.603), or MHC I proportionality ( = 0.574) between males and females. Whether it was expressed in absolute or relative units, CP was positively correlated with Hb (0.444 ≤ ≤ 0.695; < 0.05), mitochondrial protein content (0.413 ≤ ≤ 0.708; < 0.05), and MHC I proportionality (0.506 ≤ ≤ 0.585; < 0.05), and negatively correlated with τ when expressed in relative units only (-0.588 ≤ ≤ -0.527; < 0.05). Overall, CP was independent of sex, but variability in CP was related to Hb and skeletal muscle characteristics. The extent to which manipulations in these physiological parameters influence CP warrants further investigation to better understand the factors underpinning CP. In males and females matched for aerobic fitness [maximal oxygen uptake normalized to fat-free mass (FFM)], absolute critical power (CP) was greater in males, but relative CP (per kilogram body mass or FFM) was similar between sexes. CP correlated with hemoglobin mass, mitochondrial protein content, myosin heavy chain type I proportion, and skeletal muscle oxidative capacity. These findings demonstrate the importance of matching sexes for aerobic fitness, but further experiments are needed to determine causality.
关键功率（CP）代表运动表现和疲劳性的重要阈值。我们旨在确定性别、血红蛋白质量（Hb）和骨骼肌特征对 CP 的影响程度。在确定 CP 之前（即，进行 3-5 次恒定工作速率试验直至任务失败），测量 Hb 和骨骼肌氧化能力（τ），并从 12 名女性和 12 名男性中采集股外侧肌（VL）肌肉活检样本，这些男女的有氧健身与去脂体重（FFM）相匹配[平均值（SD）；V̇o：59.2（7.7）与 59.5（7.1）mL·kg·FFM·min，分别]。男性的 CP 绝对值明显大于女性[225（28）与 170（43）W；=0.001]，但相对于体重[3.0（0.6）与 2.7（0.6）W·kg·BM；=0.267]或 FFM[3.6（0.7）与 3.7（0.8）W·kg·FFM；=0.622]则不然。男性的“（≤0.030）和 Hb（≤0.016）均显著大于女性，无论采用何种归一化方法；然而，男性和女性之间的线粒体蛋白含量（=0.375）、τ（=0.603）或 MHC I 比例（=0.574）没有差异。CP 无论是以绝对值还是相对值表示，均与 Hb（0.444≤≤0.695；<0.05）、线粒体蛋白含量（0.413≤≤0.708；<0.05）和 MHC I 比例（0.506≤≤0.585；<0.05）呈正相关，与 τ 仅呈负相关（相对单位表示时为-0.588≤≤-0.527；<0.05）。总体而言，CP 与性别无关，但 CP 的变异性与 Hb 和骨骼肌特征有关。进一步研究这些生理参数的影响程度对于更好地理解 CP 的基础因素是必要的。在有氧健身（最大摄氧量与去脂体重（FFM）相匹配）相匹配的男性和女性中，男性的绝对 CP 更高，但男女之间的相对 CP（每公斤体重或 FFM）相似。CP 与血红蛋白质量、线粒体蛋白含量、肌球蛋白重链 I 型比例和骨骼肌氧化能力相关。这些发现表明，为了匹配有氧健身，匹配性别很重要，但需要进一步的实验来确定因果关系。
