Exercise Dose Response in Muscle

Exercise increases peak VO2 partially through muscle adaptations. However, understanding muscle adaptations related to exercise dose is incomplete. This study investigated exercise training dose on capillaries per fiber and capillaries per area; and citrate synthase from vastus lateralis and related both to changes in peak VO2. This randomized trial compared 3 exercise doses: low amount-moderate intensity (n = 40), low amount-high intensity (n = 47), high amount-high intensity (n = 41), and a control group (n = 35). Both measures of capillary supply increased in all exercise groups (p < 0.05). Low amount-high intensity and high amount-high intensity improved citrate synthase (p < 0.05) and the low amount-moderate intensity citrate synthase approached significance (p = 0.059). Muscle improvements were only related to improvements in peak VO2 in high amount-high intensity (citrate synthase, r = 0.304; capillaries: fiber, r = -0.318; p < 0.05 and capillaries/mm(2) r = -0.310, p < 0.05). These data suggest muscle adaptations occur following both low and high exercise doses, but are only related to improved peak VO2 following high amount-high intensity training.