Effect Of A 2-km Swim On The Cycling Power-Duration Relationship

Abstract

PURPOSE: Triathlon combines three sports (swimming, cycling, and running) into a single race and, because triathletes must cycle after the swimming, it is important to understand how cycling power may be affected by prior swimming. Therefore, the purpose of this study was to determine the effects of a 2-km swim at a self-selected race pace intensity on the cycling power-duration relationship measured during a 3-min all-out cycling test (3MT). METHODS: Eighteen trained triathletes (12 M, 6 F; 37.1 ± 10.6 years, VO2max 54.8 ± 10.1 ml·kg−1·min−1) performed two 3MTs on separate days with one 3MT immediately following a 2-km swim (swim-bike; SB) and one without prior swimming (bike only; BO). The power-duration relationship was expressed as the total work done and subdivided into the end-test power (EP) and work done above EP. To assess swimming intensity, heart rate (HR) was continuously monitored during the swim and blood lactate was assessed immediately following the 2-km swim. RESULTS: End-swim lactate was 4.2 ± 1.8 mM and mean swimming heart rate was 147 ± 18 bpm. The 2-km swim decreased total work done during the 3MT by 6% (BO: 62.8 ± 12.7 kJ; SB: 58.9 ± 13.4 kJ; p = 0.001) though neither EP (BO: 281 ± 65 W; SB: 269 ± 68 W; p = 0.102) nor work done above EP (BO: 12.1 ± 3.8 kJ; SB: 10.5 ± 4.2 kJ; p = 0.096) differed between trials. Peak power was also assessed during the 3MT and did not differ between trials (BO: 552 ± 142 W; SB: 541 ± 147 W; p = 0.097). The change in EP was inversely correlated to the change in work above EP (r = -0.624; p = 0.006). CONCLUSIONS: Total work done while cycling decreases following a 2-km race pace swim, although neither EP nor work above EP changed significantly. Triathletes may want to determine race cycling power following swimming because prior swimming affects performance during the 3MT. Future studies should look at how different swim pacing strategies affect the cycling power-duration relationship.