Background: The influence of regular breath-hold training on hematological variables is not fully understood. We monitored hematological variables in breath-hold divers (BHDs) and active controls over a year expecting both breath-hold training and seasonal effects.
Methods: In 11 recreational BHDs (36±9 years, 177±8 cm, 72±9 kg) and 12 active controls (22±2 years, 174±8 cm, 70±13 kg) monthly blood samples were analyzed with the hematological module of WADA's athlete biological passport. Hemoglobin mass and plasma volume were measured indirectly by the CO-rebreathing method for the last eight months of the study. Breath-hold training sessions were recorded online. Days without breath-hold training, or the number of hours prior to blood sampling when training was realized within the last 24 hours, were recorded.
Results: Hematology did not differ significantly between BHDs and controls over the study time (P>0.05). However, hematological values varied significantly over time for both groups suggesting seasonal effects. Blood sampling 19 hours or more after a breath hold training did not indicate any acute effects of breath holding training.
Conclusions: In comparison with a physically active lifestyle, regular breath-hold training does not induce significant variations over one year for the hematological module of the ABP.