ALTITUDE ACCLIMATIZATION IN MALE CYCLISTS

Abstract

Many studies have addressed altitude acclimatization; however, rarely has the time course of performance responses been studied. PURPOSE To determine the influence of altitude acclimatization on hematology, physiology and cycling hill-climbing performance. METHODS Seven international level U23 male cyclists (21.2 ±1.1 yr:69.9 ±5.6 kg; 176.3 ±4.9 cm; VO2peak:75.3 ±3.4 ml.kg−1.min−1) undertook 15 d of training at 2650 m. A submaximal test (ST) involving 5 min workloads at 150, 200 and 250 W was completed at sea level (BASE) and on days 3, 8 and 15 at altitude (ALT). Blood lactate (BLa), heart rate (HR), rating of perceived exertion (RPE) and hematocrit (Hct) were recorded for each workload. At BASE and on days 7 and 14 at ALT, each cyclist completed an approx 5.5 km maximal hill-climbing performance test (MHC) on his own bicycle fitted with an SRM crank. Total time, average power, cadence, speed, HR and post BLa and RPE were recorded. RESULTS From BASE to ALT3, increases in BLa (1.3 vs 3.2 mmol.l−1), HR (141 vs 166 bpm) and Hct (44.5 vs 48.9%) were most evident at 250 W (p ≤ 0.05). These parameters returned towards BASE values on ALT8 and 15. The change in Hct for the ST workloads was minor at BASE (43.6 vs 44.1 vs 44.5% at 150, 200, 250 W, respectively) and remained so at ALT. MHC average power for BASE (368 ±66 W) was higher (p ≤ 0.05) than ALT7 (268 ±48 W) and ALT14 (301 ±61 W), with no differences for BLa, HR or RPE. The increase in MHC power (W.kg−1) from ALT7 to ALT14 was best predicted by the decrease in ST HR at 250 W (r = −0.96; p ≤ 0.05). CONCLUSIONS Heart rate at a submaximal workload tracked changes in cycling hill-climbing performance at altitude. After two weeks of acclimatization, hill-climbing performance remained suppressed by 18% compared with BASE, despite the return of HR, Hct and RPE at submaximal workloads. Research funds provided by the Australian Sports Commission and Cycling Australia.