Hematological variables in recreational breath-hold divers: a longitudinal study.

Abstract

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. 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. 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. 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.