Physical Fitness and Perfomance Effects of High- and Moderate-Intensity Training on Metabolism and Repeated Sprints JOHANN EDGE, DAVID BISHOP, CARMEL GOODMAN, and BRIAN DAWSON School of Human Movement and Exercise Science, The University of Western AUSTRALIA, Perth, AUSTRALIA ABSTRACT EDGE, J., D. BISHOP, C. GOODMAN, and B. DAWSON. Effects of High- and Moderate-Intensity Training on Metabolism and Repeated Sprints. Med. Sci. Sports Exerc., Vol. 37, No. 11, pp. 1975–1982, 2005. Purpose: We compared the effects of high-intensity interval (HIT) and moderate-intensity continuous (MIT) training (matched for total work) on changes in repeated-sprint ability (RSA) and muscle metabolism. Methods: Pre- and posttraining, V ˙ O 2peak , lactate threshold (LT), and RSA (5  6-s sprints, every 30 s) were assessed in 20 females. Before and immediately after the RSA test, muscle biopsies were taken from the vastus lateralis. Subjects were matched on RSA, randomly placed into the HIT (N = 10) or MIT (N = 10) group and performed 5 wk (3 d·wk -1 ) of cycle training; performing either HIT (6 –10, 2-min intervals at 120 –140% LT) or MIT (continuous, 20 –30 min at 80 –95% LT). Results: Both groups had significant improvements in V ˙ O 2peak (10 –12%; P  0.05) and LT (8 –10%; P  0.05), with no significant differences between them. Both groups also had significant increases in RSA total work (kJ) (P  0.05), with a significantly greater increase following HIT than MIT (13 vs 8.5%, respectively; P  0.05). There was a significant decrease in resting [ATP] and an increase in postexercise [La - ] b for both groups, but no significant differences between them. There were no significant changes in resting or postexercise [PCr], [Cr], muscle [La - ], or [H + ] after the training period. Conclusions: When total work is matched, HIT results in greater improvements in RSA than MIT. This results from an improved ability to maintain performance during consecutive sprints, which is not explained by differences in work done during the first sprint, aerobic fitness or metabolite accumulation at the end of the sprints. Key Words: TRAINING VOLUME, TRAINING INTENSITY, TEAM-SPORTS, TOTAL WORK T eam-sport games such as soccer, hockey and basket- ball require participants to perform a number of short sprints, interspersed with periods of rest or low- to moderate-intensity activity. Many of these sprints are sep- arated by rest periods long enough (1 min) to allow complete or near complete recovery and therefore subse- quent sprint performance is not significantly impaired. However, recent game analysis has shown that some of these sprints are separated by short rest periods (30 s) (26), which have been shown to negatively affect subse- quent sprint performance (1). Therefore, one of the fitness requirements of team-sport athletes is the ability to perform short-duration sprints (10 s) with a short recovery time (30 s). This fitness requirement has been termed repeated- sprint ability (RSA). However, the effects of different train- ing methods on RSA is unclear. Sprint training studies have reported improvements in longer (30 s) repeated-sprint performance (11,19). However, few reports have investigated the effects of training on short (10 s) repeated-sprint performance, similar to that encoun- tered in team sports. To date, studies that have investigated training adaptations to repeated short sprints (10 s) have all employed short (10 s), repeated sprints as the training stimulus (15,22). Whereas training that is specific to the task, that is, short sprints, may be the most beneficial train- ing modality to improve RSA, training methods that im- prove other fitness characteristics, such as endurance capac- ity, may also affect RSA. One method by which endurance training may affect RSA is by improving metabolic recovery between sprints. An improved metabolic recovery may reduce the decline in sprint performance that occurs when a number of sprints are performed in a short period of time. For example, athletes with a greater oxidative capacity have been reported to have a greater PCr resynthesis and ability to remove lactate/ hydrogen ions (La - /H + ) from skeletal muscle (20,23). Both the resynthesis of PCr (6) and the accumulation of H + have been related to RSA (3). Endurance training may also im- prove the ability to deliver and use oxygen during and Address for correspondence: David Bishop, Team Sport Research Group, School of Human Movement and Exercise Science, The University of Western Australia, Perth, Australia; E-mail: dbishop@cyllene.uwa.edu.au. Submitted for publication December 2004. Accepted for publication June 2005. 0195-9131/05/3711-1975/0 MEDICINE & SCIENCE IN SPORTS & EXERCISE ® Copyright © 2005 by the American College of Sports Medicine DOI: 10.1249/01.mss.0000175855.35403.4c 1975