Stability of Hemoglobin Mass During a 6-Day UCI ProTour Cycling Race

Objective: Blood doping in endurance sport is a growing problem. The purpose of this study was to determine the reliability of total hemoglobin mass (Hb(mass)) measurement in the field and to establish the variability of Hb(mass) during a cycling race, to assess its viability as an additional antidoping detection parameter. Design: Control-matched longitudinal study. Setting: International Cycling Union's (UCI) ProTour stage race. Participants: Six professional cyclists and 5 recreationally active controls. Interventions: Seventy-two Hb(mass) tests using the optimized carbon monoxide rebreathing method were performed over 7 consecutive days, before and throughout the tour. Fasted venous blood was obtained for measurement of hematocrit (Hct) and hemoglobin concentration [Hb] in the morning before stages 1, 3, and 6 (D(1), D(3), and D(6)). Main Outcome Measures: Reliability of Hb(mass) measurement was established using typical error calculated from 2 baseline measures. Individual change scores and coefficients of variation were used to assess stability during racing. Results: Typical error for Hb(mass) was 1.3% [95% confidence limits (CL): 0.9%, 2.5%]. Calculated 95% and 99.99% CL for percent change in Hb(mass) were +/- 3.6% and +/- 7.2%, respectively. Mean Hb(mass) remained within +/- 1.9% of baseline in cyclists and +/- 0.5% in controls. In all cases, individual change scores for both cyclists and controls fell within the 95% CL. There was a decrease in Hct (8.1%+/- 2.8%) and [Hb] (9.7%+/- 3.2%) throughout the tour in cyclists but not in controls. Conclusions: We demonstrate that Hb(mass) can be measured reliably via CO-rebreathing during a cycling tour. Unlike [Hb] and Hct, Hb(mass) remains stable over 6 days of racing in professional cyclists and may have potential in an antidoping context.