The effects of strength training on endurance performance and muscle characteristics

Purpose: The purpose of this study was to determine the effects of resistance training on endurance performance and selected muscle characteristics of female cyclists. Methods: Twenty-one endurance-trained, female cyclists, aged 18-42 yr, were randomly assigned to either a resistance training (RT; N = 14) or a control group (CON; N = 7). Resistance training (2X.wk(-1)) consisted of five sets to failure (2-8 RM) of parallel squats for 12 wk. Before and immediately after the resistance-training period, all subjects completed an incremental cycle test to allow determination of both their lactate threshold (LT) and peak oxygen consumption (V) over dot O-2). In addition, endurance performance was assessed by average power output during a l-h cycle test (OHT), and leg strength was measured by recording the subject's one repetition maximum (1 RM) concentric squat. Before and after the 12-wk training program, resting muscle was sampled by needle biopsy from m. vastus lateralis and analyzed for fiber type diameter, fiber type percentage, and the activities of 2-oxoglutarate dehydrogenase and phosphofructokinase, Results: After the resistance training program, there was a significant increase in I RM concentric squat strength for RT (35.9%) but not for CON (3.7%) (P < 0.05). However, there were no significant changes in OHT performance, LT, (V) over dot O-2 muscle fiber characteristics, or enzyme activities in either group (P > 0.05). Conclusion: The present data suggest that increased leg strength does not improve cycle endurance performance in endurance-trained, female cyclists.