Tripp Thomas R, Kontro Hilkka, Gillen Jenna B, MacInnis Martin J
Human Performance Lab, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.
Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada.
J Physiol. 2025 Apr;603(8):2219-2230. doi: 10.1113/JP287735. Epub 2025 Mar 22.
More studies in exercise physiology are investigating sex as a biological variable, but the potential confounding effect of cardiorespiratory fitness is often neglected. As maximal oxygen uptake ( ) correlates with many physiological outcomes at rest and in response to exercise, differences in between male and female participants may hinder interpretation. Here we revisit decades-old arguments that advocate for matching males and females for normalized to fat-free mass (FFM) when investigating sex differences in the context of exercise. The rationale for using FFM to normalize , as opposed to total body mass, is that females, on average, have a greater proportion of body fat than males and body fat does not contribute to . Using a multistudy dataset of males (n = 54) and females (n = 54) matched for per FFM, we illustrate the different approaches to normalization and the effects of poor or incorrect matching on interpretation. Modern assessments of body composition allow for segregation of bone from total FFM and regional measures of body composition; however neither approach seems to be an improvement on whole-body FFM as the normalization factor for . A group-level difference of less than 5% for per unit FFM is a strong starting point for comparisons between males and females, but the allowable difference depends on the extent to which cardiorespiratory fitness influences the variable of interest and other competing study design decisions. Researchers should be encouraged to normalize to FFM for exercise physiology studies investigating sex differences.
越来越多的运动生理学研究将性别作为一个生物学变量进行调查，但心肺适能的潜在混杂效应常常被忽视。由于最大摄氧量（ ）与静息及运动时的许多生理指标相关，男性和女性参与者之间最大摄氧量的差异可能会妨碍对结果的解读。在此，我们重新审视数十年前的观点，即在研究运动背景下的性别差异时，主张根据去脂体重（FFM）对男性和女性的最大摄氧量进行匹配。使用FFM对最大摄氧量进行标准化，而不是总体重的理由是，平均而言，女性的体脂比例高于男性，且体脂对最大摄氧量没有贡献。我们使用一个多研究数据集，其中男性（n = 54）和女性（n = 54）按每FFM的最大摄氧量进行匹配，展示了最大摄氧量标准化的不同方法以及匹配不佳或错误对解读的影响。现代身体成分评估方法能够将骨骼与总FFM分离，并对身体成分进行区域测量；然而，作为最大摄氧量的标准化因子，这两种方法似乎都不比全身FFM有改进。每单位FFM的最大摄氧量的组间差异小于5%是男性和女性之间比较的一个强有力的起点，但允许的差异取决于心肺适能对感兴趣变量的影响程度以及其他相互竞争的研究设计决策。对于研究性别差异的运动生理学研究，应鼓励研究人员将最大摄氧量按FFM进行标准化。
