Ef. Coyle, CARDIOVASCULAR DRIFT DURING PROLONGED EXERCISE AND THE EFFECTS OF DEHYDRATION, International journal of sports medicine, 19, 1998, pp. 121-124
Reductions in SV are the most striking component of ''classic'' CV dri
ft as well as ''dehydration induced'' CV drift. Direct data for the wi
despread notion that increased skin blood flow causes SV to be reduced
during ''classic'' CV drift is rather scarce. Reductions in SV due to
dehydration and concomitant hyperthermia are clearly not due to incre
ases in skin blood flow. Instead, skin blood flow declines as skin and
systemic vascular resistance increase as the CV system attempts to co
pe with the severe challenge of large reductions in cardiac output. Ap
proximately one-half of the reduction in SV is due to reduced blood vo
lume from dehydration during exercise which produces hyperthermia. The
remaining reduction in SV with dehydration and hyperthermia appears t
o be related to additional factors such as hyperthermia and their inte
raction with factors that further reduce ventricular filling, such as
heart rate acceleration.