Abstract

--- - Purpose - The purpose of the current study was to investigate the effects of adding strength training to normal endurance training on running performance and running economy in well-trained female athletes. We hypothesized that the added strength training would improve performance and running economy through altered stiffness of the muscle-tendon complex of leg extensors. - Methods - "Nineteen female endurance athletes [maximal oxygen consumption (VO2max): 53 +/- 3 ml.kg(-1).min(-1), 5.8 h weekly endurance training] were randomly assigned to either normal endurance training (E, n = 8) or normal endurance training combined with strength training (E+S, n = 11). The strength training consisted of four leg exercises [3 x 4-10 repetition maximum (RM)], twice a week for 11 weeks. Muscle strength, 40 min all-out running distance, running performance determinants and patellar tendon stiffness were measured before and after the intervention." - Results - E + S increased 1RM in leg exercises (40 +/- 15%) and maximal jumping height in counter movement jump (6 +/- 6%) and squat jump (9 +/- 7%, p < 0.05). This was accompanied by increased muscle fiber cross sectional area of both fiber type I (13 +/- 7%) and fiber type II (31 +/- 20%) in m. vastus lateralis (p < 0.05), with no change in capillary density in m. vastus lateralis or the stiffness of the patellar tendon. Neither E + S nor E changed running economy, fractional utilization of VO2max or VO2max. There were also no change in running distance during a 40 min all-out running test in neither of the groups. - Conclusion - Adding heavy strength training to endurance training did not affect 40 min all-out running performance or running economy compared to endurance training only.