Physiological adaptations to interval training to promote endurance

The physiological determinants of endurance exercise performance are complex but depend in part on the capacity of the cardiorespiratory system to transport oxygenated blood to working skeletal muscle, and the oxidative capacity of skeletal muscle, which is largely determined by mitochondrial content. Interval training — characterized by intermittent bouts of higher intensity exercise interspersed by periods of lower-intensity exercise or complete rest for recovery within a given session — enhances endurance exercise performance including in those who are already well trained, although the mechanisms may be different as compared to less-trained individuals. This brief review considers the evidence for cardiac and skeletal muscle responses to interval training that are associated with an improved capacity for whole-body aerobic energy provision, with a focus on recent findings.