Myocellular basis for tapering in competitive distance runners

purpose of this study was to examine the effects of a 3-wk taper on the physiology of competitive distance runners. We studied seven colle-giate distance runners (20 1 yr, 66 1 kg) before and after a 3-wk taper. The primary measures included 8-km cross-country race per-formance, gastrocnemius single muscle fiber size and function (peak force, shortening velocity, and power), baseline and exercise-induced gene expression 4 h after a standardized 8-km run, citrate synthase activity, and maximal and submaximal cardiovascular physiology (oxygen consumption, ventilation, heart rate, and respiratory ex-change ratio). Race performance improved by 3 % following taper (P 0.05). Myosin heavy chain (MHC) IIa fiber diameter (7%, P 0.05), peak force (11%, P 0.06), and absolute power (9%, P 0.05) increased following taper. In addition to the MHC IIa adaptations, taper elicited a distinct postexercise gene response. Spe-cifically, the induction of MuRF-1 was attenuated following taper