Skeletal muscle oxygen dynamics and peak aerobic capacity

Abstract

Skeletal muscle O2 dynamics can be measured during whole body dynamic exercise noninvasively by near-infrared spectroscopy (NIRS), and muscle O2 dynamics can allow us to estimate muscle O2 extraction. Muscle O2 extraction is one of the determinants of peak pulmonary O2 uptake (V O2 ), and blunted peak V O2 potentially increases cardiovascular-associated morbidity and mortality. However, muscle O2 dynamics and their relation to reduced peak aerobic capacity have not been fully established. This review briefly outlines the relationship between change in muscle O2 dynamics and an improvement of peak V O2 . Our findings suggest that aerobic training enhances estimated muscle O2 extraction, and the enhancement is related to an improvement of peak aerobic capacity in elderly subjects, with and without heart disease. The relationship may be potentially affected, however, by some factors such as: the initial level of aerobic capacity and cardiac function (ability of convective O2 supply), and training volume, phase, or type. The number of elderly people who have a low peak aerobic capacity will most likely be increasing in Japan, as a consequence of the aging population and physical inactivity due to advanced technology. Although we recognize several limitations of the NIRS technique and the necessity for further investigation, assessing muscle O2 dynamics is valuable to understand the peripheral impairments and mechanisms of lowered peak VO2 .