SKELETAL-MUSCLE BUFFERING CAPACITY AND ENDURANCE PERFORMANCE AFTER HIGH-INTENSITY INTERVAL TRAINING BY WELL-TRAINED CYCLISTS

Skeletal muscle buffering capacity (beta m), enzyme activities and exe rcise performance were measured before and after 4 weeks of high-inten sity, submaximal interval training (HIT) undertaken by six well-traine d competitive cyclists [mean maximal oxygen consumption (VO2max) = 66. 2 ml . kg(-1). min(-1)]. HIT replaced a portion of habitual endurance training and consisted of six sessions, each of six to eight repetitio ns of 5 min duration at 80% of peak sustained power output (PPO) separ ated by 1 min of recovery. beta m increased from 206.6 (17.9) to 240.4 (34.1) mu mol H+. 9 muscle dw(-1). pH(-1) after HIT (P = 0.05). PPO, time to fatigue at 150% PPO (TF150) and 40-km cycle time trial perform ance (TT40) all significantly improved after HIT (P < 0.05). In contra st, there was no change in the activity of either phosphofructokinase or citrate synthase. In addition, beta m correlated significantly with TT40 performance before HIT (r = -0.82, P < 0.05) and the relationshi p between change in beta m and change in TT40 was close to significanc e (r = -0.74). beta m did not correlate with TF150. These results indi cate that beta m may be an important determinant of relatively short-d uration (< 60 min) endurance cycling activity and responds positively to just six sessions of high-intensity, submaximal interval training.