A standard blood bank donation alters the thermal and cardiovascular responses during subsequent exercise

The fear for adverse effects of blood donation on subsequent exercise may prevent physically active people from donating. We studied the impact of a standard blood bank donation (i.e., 450-mL blood withdrawal) on the thermoregulatory and cardiovascular responses to prolonged exercise in the heat.

Eight moderately trained, heat-acclimated males cycled for 1 hour at 60% in a hot environment (34.9±0.6 °C) on four occasions: 1) 2 days before blood donation (CON), 2) 2 hours after donation (DON), 3) 2 days after donation (2 DAYS), and 4) 7 days after donation (7 DAYS).

Two-thirds of the blood volume withdrawn was endogenously restored before exercise in the DON trial (p<0.05). DON started with increased preexercise rectal temperature (TRE; 0.42±0.1 °C above CON; p<0.05), which resulted in high levels of hyperthermia (i.e., 39.0±0.2 °C) after 1 hour of exercise. Skin temperature (34.5±0.1 °C) and sweat rate (1.15±0.1 L/h) were not affected by DON. However, DON lowered the skin blood flow:TRE relationship and elevated heart rate (HR) above CON (12±4 beats/min; p<0.05) maintaining cardiac output. After 2 DAYS, TRE and HR were restored to CON levels while cardiac output increased above CON (6%; p<0.05) in association with reduced hemoglobin concentration (i.e., peak hemodilution).

A blood bank donation increases preexercise TRE. Subsequent exercise in a hot environment results in high levels of hyperthermia and HR. These thermoregulatory and cardiovascular perturbations observed during exercise disappear 2 days after donation.