Introduction: Equivocal findings exist on the effect of adding strength training (S) to endurance training on running and cycling performance (1-4). However, the effect of S on running and cycling in the same athletes has not been investigated. Thus, the present study investigated the effects of S on running and cycling performance and muscle fiber composition in duathletes. Methods: Nineteen females (33±8 years, 64±7 kg, VO2max cycling: 54±3 ml/kg/min, VO2max running: 53±3 ml/kg/min) were randomly assigned to either usual endurance training combined with S (E+S, n=11) or to usual endurance training only (E, n=8). The S consisted of four lower body exercises [3x4-10 repetition maximum (RM)] twice a week for 12 wk. Running and cycling performance was evaluated by a 5-min all-out test after a prolonged period of submaximal work (1.5 h at 60% of Vmax in running and 3 h at 45% of Wmax in cycling). Muscle biopsies from m. vastus lateralis were analyzed for muscle fiber composition by immunohistochemistry. Results: There were no differences between the groups at baseline. E+S increased 1RM in leg press more than E (39±19% vs. 6±9%, p<0.01). Body mass was reduced in E (1.4±1.2%, p<0.01), with no change in E+S. E+S increased body mass adjusted mean power output in the 5-min all-out cycling test by 7±5% (p<0.01) while no change occurred in E. Effect size (ES) analyses revealed a moderate effect on percent performance improvements of E+S vs E (ES=0.62). In the 5 min running test E+S improved the running distance more than E (5±6% vs. -1±5%, p=0.05, ES= 0.95). E+S reduced VO2 during the last hour of the prolonged cycling (-3±4%, p=0.04) while no changes occurred in E with a moderate effect of E+S vs. E at 180 min (ES=1.10). No changes occurred in VO2 during the prolonged running. The proportion of fibers positive for IIA and IIX myosin heavy chain was reduced from 9±7% to 0% in E+S (p=0.01) with a concomitant increase in type IIA fibers (39±13% to 51±10%, (p=0.01). No changes occurred in E. The correlation between change in all-out performance and change in IIAX fibers was r=-0.54 (p=0.03) in cycling and r=-0.51 in running (p=0.04). Discussion: The main finding was that adding S to usual endurance training in female athletes improved all-out performance after prolonged submaximal work in both cycling and running. This seems to be related to reduction in type IIAX muscle fibers. In addition E+S reduced VO2 during the last hour of prolonged cycling. These findings are in agreement with studies in both cycling (1) and running (3) but contradict other studies (2, 4).
© Copyright 2014 19th Annual Congress of the European College of Sport Science (ECSS), Amsterdam, 2. - 5. July 2014. Veröffentlicht von VU University Amsterdam. Alle Rechte vorbehalten.