This project studies the effect of voluntary apnea or breath-holding on exercise tolerance. Acute apnea evokes two important responses, (1) a strong spleen contraction releasing red blood cells into the blood circulation (thus increasing hemoglobin, Hb) and (2) an acute increase in Erythropoietin (EPO), the hormone responsible for the formation of red blood cells. These response are expected to increase blood transport and storage capacity for oxygen (O2), either immediately following apnea (due to spleen contraction) or following an apnea training program (due to increased EPO levels). As O2 transport capacity is one of the main performance determining factors in multiple sports, the responses to apnea have the potential to improve
exercise performance and tolerance. This project aims first to determine the optimal modalities (i.e., inducing the highest increase in Hb and EPO) of an acute apnea session and an apnea training program to increase O2 carrying capacity of the blood. Second, it will be tested whether an acute apnea session as well as an apnea training program (with the optimal modalities to increase the O2 carrying capacity determined from work package I) are effective in improving exercise tolerance. Third, it will be assessed whether this training method is feasible, therapy supportive and effective in facilitating physical activity and optimizing quality of life in a patient population in which O2 delivery to the muscles is limited.