Haemoglobin concentration [Hb] and haematocrit (Hct) generally decrease in response to multiple days of cycle racing due to a plasma volume expansion. In contrast, preliminary evidence suggests that Haemoglobin mass (tHb) remains stable during short stage races. The aim of this study was to document the variability of tHb, [Hb], and Hct in cyclists participating in a UCI ProTour event. Method tHb was measured using the carbon monoxide rebreathing test in 6 male cyclists (CYC; Mean ± SD age 24 ± 5y, height 179 ± 5cm, mass 71 ± 4kg) and 5 controls (CON; 31 ± 6y, 179 ± 6cm, 74 ± 6kg) throughout an international calibre stage race (Tour Down Under, UCI Pro Tour). The 6-day race covered 802 km in 19.5 h of racing during the Australian summer (24-39 C). tHb was measured on 7 consecutive days. Results from the first two tests were averaged to establish Baseline. On race days, tHb was measured daily within 4 h of the stage finish. No measures were performed on the last race day. Early morning, fasted venous blood samples were collected 2 d before the start of the tour (D0), after 2 d of racing (D4) and prior to the last stage (D6) in accordance with UCI guidelines. Venous blood was collected into an EDTA Vacutainer, and analysed within 12 h of collection for Hct and [Hb]. The reliability of the tHb technique was presented as a Typical Error (TE). Mean effects of log-transformed data were estimated via the unequal-variances t statistic computed for change scores between tests. A coefficient of variation (CV) was calculated for each subject to assess within-subject daily variability. Results TE for tHb at Baseline (n=11) was 1.3%. tHb of the CYC remained within ± 1.9% (20g) of baseline (mean ± SD; 997 ± 67g) throughout the tour (range: -1.9% D5 to 1.3% D2). Mean tHb of CON remained within 0.5% (5g) of baseline (D0 = 901 ± 113g) during the same period. There were no substantial differences in the daily change scores between CYC and CON. The mean CV for tHb during the tour was 1.5% in CYC vs. 1.2% in CON. Individual CVs ranged from 0.3-2.3% in CYC and from 0.7-1.7% in CON. CYC Hct (D0 = 0.44 ± 0.02) decreased by 5.7 ± 2.9 % at D4 and 8.1 ± 2.8 % at D6. However, CON Hct (D0 = 0.46 ± 0.01) was similar on D4 but 3.3 ± 2.6% lower on D6. CYC [Hb] (D0 = 154 ± 6.4 g.L-1) decreased by 7.7 ± 3.8% at D4 and 9.7 ± 3.2% at D6. CON [Hb] (D0 = 149 ± 9.6 g.L-1) remained similar on D4 and D6. The decrease in [Hb] at D6 was substantially lower in CYC vs CON (p=0.003). Discussion Similar to previous observations, a warm 6 d stage race can decrease Hct (~8%) and [Hb] (~10%) in professional road cyclists. In contrast, the individual CV for tHb was less than 2.5% in all cases suggesting that tHb remains relatively stable. These data indicate that a change from baseline values by as much as 2.5% during a 1 week stage race could be considered "normal". Further research is required to establish the normal variability of tHb during 1-3 wk stage races in elite cyclists.
© Copyright 2009 14th annual Congress of the European College of Sport Science, Oslo/Norway, June 24-27, 2009, Book of Abstracts. Published by The Norwegian School of Sport Sciences. All rights reserved.