The influence of biological sex, hemoglobin mass, and skeletal muscle characteristics on cycling critical power
Date
2023-09-20
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Abstract
Critical power (CP) represents an important threshold for exercise performance and fatiguability. We sought to determine the extent to which biological sex, hemoglobin mass (Hbmass), skeletal muscle mitochondrial content and fibre type influences CP. Prior to CP determination (i.e., 3-5 constant work rate trials to task failure), Hbmass was measured and vastus lateralis muscle biopsy samples were collected from 12 females and 12 males matched for aerobic fitness (V̇O2max: 59.2±7.7 vs. 59.5±7.1 mL·kg FFM-1·min-1). Males had a significantly greater CP than females when expressed in absolute terms (p=0.001), but there was no sex difference when expressed relative to BM (P=0.267) or FFM (p=0.622). Males had significantly greater W’ in absolute units (p<0.001), relative to BM (p=0.001), and relative to FFM (p=0.016). Males also had a significantly greater Hbmass in absolute units (p<0.001), relative to BM (p<0.001), and relative to FFM (p=0.016). There was no sex difference in mitochondrial content (p=0.375) or MHC I (p=0.574) proportionality. Whether CP was expressed in absolute (W) or relative units (W·kg BM-1 or W·kg FFM-1), there were significant positive correlations between CP and Hbmass (0.436≤r≤0.695; p<0.05) and mitochondrial content (0.413≤r≤0.708; p<0.05). There were significant positive correlations between relative CP (W·kg BM-1 or W·kg FFM-1) and MHC I proportionality (0.506≤r≤0.585; p<0.05). Overall, there was no sex difference in relative CP when males and females were matched for aerobic fitness, and variability in CP was related to Hbmass, mitochondrial content, and MHC I proportionality. The extent to which manipulations in these parameters influence CP warrants further investigation.
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Keywords
exercise physiology, sex differences, mitochondrial content, hemoglobin mass, fibre type, critical power
Citation
Caswell, A. (2023). The influence of biological sex, hemoglobin mass, and skeletal muscle characteristics on cycling critical power (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.