Is maximal oxygen consumption an appropriate metric for metabolichealth?

Cardiorespiratory ftness (CRF), assessed by maximal oxygen consumption (V̇ O2 max) testing, is a strong predictor of chronic disease and all-cause mortality. However, recent evidence suggests that V̇ O2 max may lack specifcity and sensitivity in assessing metabolic health, particularly mitochondrial function, which is associated with metabolic diseases such as type 2 diabetes, insulin resistance, and metabolic syndrome. While aerobic training leads to improvements in mitochondrial function, studies have found a disparity between V̇ O2 max and mitochondrial content, with some individuals showing increases in mitochondrial oxidative capacity without changes in V̇ O2 max. Furthermore, the criteria used to determine V̇ O2 max, such as the plateau in oxygen consumption, may not be achieved by all individuals, leading to inaccurate assessments. Technological advances in metabolomics and lipidomics may provide insights into metabolic health, but their cost and practicality for routine use in clinical settings remain a challenge. Alternatively, indirect calorimetry during submaximal exercise has shown promise as a non-invasive marker of mitochondrial function and metabolic fexibility. However, further research is needed to establish appropriate protocols and analyses for various populations.