Exercise intensity during competition time trials in professional road cycling

PURPOSE: To estimate, upon competition heart rate (HR), exercise intensity during time trials (TT) in professional road cycling. METHODS: Eighteen world-class cyclists completed an incremental laboratory cycling test to assess maximal power output (Wmax), maximal HR (HRmax), onset of blood lactate accumulation (OBLA), lactate threshold (LT), and a HR-power output relationship. An OBLA(ZONE) (HR(OBLA) +/- 3 beats x min(-1)) and a LT(ZONE) (HR(LT) +/- 3 beats x min(-1)) were described. HR was monitored during 12 prologue (40 km, LTT), eight uphill (UTT), and seven team (TTT) time trials. A HR-power output relationship was computed to estimate each cyclist's power output during TT racing from competition HR. Competition training impulse (TRIMP) values were estimated from HR and race duration. RESULTS: %HRmax were 89+/-3%, 85+/-5%, 80+/-5%, 78+/-3%, and 82+/-2% in PTT, STT, LTT, UTT, and TTT, respectively. The amount of TRIMP were, respectively, 21+/-3, 77+/-23, 122+/-27, 129+/-14, and 146+/-6. Competition HR values relative to HR(OBLA) and HR(LT) were, respectively, 100+/-3%, 114+/-8% in PTT, 95+/-7%, 108+/-9% in STT, 89+/-5%, 103+/-8% in LTT, 87+/-2%, 101+/-5% in UTT, and 91+/-4%, 105+/-11% in TTT. CONCLUSIONS: %HRmax, TRIMP and time distribution around HR(OBLA) and HR(LT) reflected the physiological demands of different TT categories. HR(OBLA) and HR(LT) were accurate intensity markers in events lasting, respectively, or =30 min (LTT, UTT, TTT).