HEMATOLOGICAL RESPONSE TO AN 11-D RACE IN INTERNATIONALLY COMPETITIVE FEMALE CYCLISTS

Abstract

We examined the effects of an international women's cycling stage race (11-d, 1010 km, 27 h, 610–2377m) on hemoglobin (HB), hematocrit (HCT), reticulocytes (RET) and plasma volume (PV). Data were analyzed to determine whether these hematological parameters were different in cyclists placing top25 (N = 8, 1–24 place) compared to non-top25 (N = 15, 26–79 place). Cyclists from 7 countries (N = 24; 27.6 ± 4.7 yr; 170.5 ± 5.5 cm; 62.7 ± 5.5 kg) gave venous blood samples (10 ml) on three separate days (D1, D7, D11) prior to exercise and breakfast. HCT, HB and RET were measured using an automated flow cytometry technique within 36 h of collection. PV shifts were estimated using HB and HCT. The characteristics of the blood samples were not compatible with recent exogenous EPO use. Overall, racing (D1 vs D11) was associated with a decrease in HB (14.2 ± 0.5 vs 13.5 ± 0.6 g.dL−1, p < 0.05) and HCT (41.7 ± 1.6 vs 40.6 ± 2.0%, P = 0.07) but an increase in RET (1.5 ± 0.5 vs 1.9 ± 0.4%, p < 0.05). 11 d of racing produced a 7.8 ± 8.3% PV expansion. On D1, only RET were different between top25 and nontop25 (1.2 ± 0.3% vs 1.6 ± 0.5%, p < 0.05). The lower RET in successful cyclists was also observed on D7 and D11. These data suggest that stage racing at moderate altitude produces 1) a decrease in HCT and HB primarily due to a plasma volume expansion and 2) an increase in RET. For HCT and HB, absolute values and response to racing were similar in top25 vs non-top25 cyclists. Further research is required to establish why RET were lower in successful cyclists throughout the stage race. Funded by an IOC-Australian Government EPO2000 Grant