Objective: Blood doping in endurance sport is a growing problem. The purpose of this study was to determine the reliability of total hemoglobin mass (Hbmass) measurement in the field and to establish the variability of Hbmass 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 Hbmass 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 (D1, D3, and D6).
Main Outcome Measures: Reliability of Hbmass 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 Hbmass was 1.3% [95% confidence limits (CL): 0.9%, 2.5%]. Calculated 95% and 99.99% CL for percent change in Hbmass were ±3.6% and ±7.2%, respectively. Mean Hbmass 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 Hbmass can be measured reliably via CO-rebreathing during a cycling tour. Unlike [Hb] and Hct, Hbmass remains stable over 6 days of racing in professional cyclists and may have potential in an antidoping context.