Effects of Heavy Strength Training on Running Performance and Determinants of Running Performance in Female Endurance Athletes

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.

Fig 1. Maximal strength and jumping performance.

Individual values (dotted lines) and mean values (solid lines) before (Pre) and after (Post) the intervention period for athletes adding strength training to their normal endurance training (E+S) and athletes performing normal endurance training only (E). a: Squat jump (SJ) height. b: Counter movement jump (CMJ) height. c: Mean 1 repetition maximum (1RM) in half-squat and one-legged leg press (leg exercises). * Different from pre (p ˂ 0.05), # significant interaction between group and time (p ˂ 0.05)

Fig 2. Muscle fiber cross sectional area.

Individual values (dotted lines) and mean values (solid lines) before (Pre) and after (Post) the intervention period for athletes adding strength training to their normal endurance training (E+S, left panel) and athletes performing normal endurance training only (E, right panel). Muscle fiber cross sectional area (CSA) for both type I muscle fibers and type II muscle fibers * Different from pre (p ˂ 0.05)

Fig 3. Capillarization.

Individual values (open symbols) and mean values (solid squares) for athletes adding strength training to their normal endurance training (E+S) and athletes performing normal endurance training only (E). a: Percent change in capillaries around each muscle fiber (CAF) for both muscle fiber type I and muscle fiber type II for E+S and E. b: Percent change in capillaries related to fiber area (CAFA) for both muscle fiber type I and muscle fiber type II for E+S and E.

Fig 4. Determinants of running performance and running performance.

Individual values (dotted lines) and mean values (solid lines) before (Pre) and after (Post) the intervention period for athletes adding strength training to their normal endurance training (E+S) and athletes performing normal endurance training only (E). a: Body mass adjusted oxygen consumption at 10 km·h^-1. b: Running velocity at 3.5 mmol∙L^-1 [la^-] calculated during the blood lactate profile test. c: The fractional utilization of VO_2max during the 40 min all-out test. d: Running distance during the 40 min all-out test. * Different from pre (p ˂ 0.05).