Exercise dose response in muscle

Exercise increases peak VO ₂ 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 VO ₂. 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 VO ₂ 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 VO ₂ following high amount-high intensity training.