The influence of an 8 hour flight on haematological variables used in the athletes' biological passport of WADA

WADA's biological passport uses Hb and Ret% as markers for detection of blood doping. Athletes often have to travel long distances when they go for competition or training camps. Thus it is a legitimate discussion if the influence of travelling has a significant impact on these markers. For that reason the aim of this study was to investigate Hb and Ret% before and after a day of travelling including a flight of 8 h. 15 male endurance athletes performed a 14 h journey including an 8 h flight. Hydration status, bodyweight and fluid intake was controlled. Blood was sampled in the morning and evening of day 1 and day 2 for interday comparisons and to control if intraday fluctuations are a result of travelling or circadian rhythm. Day 1 The subject`s bodyweight did not show a significant difference between the two timepoints of day 11, with 72.9±5.9 kg in the morning and 72.5±5.8 kg in the evening. The subjects showed a positive fluid balance of 982±780 ml. Hb showed a significant decrease from 14.5±0.6 g/dl to 14.0±0.6 g/dl while Ret% remained unchanged (1.09±0.25% vs 1.03±0.29%). Day 2 The bodyweight of the subjects was 71.9±5.8 kg in the morning and 72.9±5.7 kg in the evening. The fluid balance was 407±908 ml. The high SD is a sign that some of the subjects had a negative fluid balance, which was the case for four subjects. Hb showed a significant decrease from 14.9±0.6 g/dl to 14.2±0.5 g/dl while Ret% remained unchanged (1.03±0.30% vs 1.06±0.32%). The homeostasis of the human body regarding its fluid balance and hydration remains stable during changing environmental conditions which occur at a typical travel day including an 8 h flight. We conclude that an 8 h flight does not change the haematological variables used in the biological passport in a bigger range than by circadian fluctuations. Thus blood samples after flights up to 8 h can be used for the interpretation in antidoping.