"Thermoregulation
The transport functions of the blood during exercise
are not only that of supplying active muscle with fuel
and oxygen and carrying away the metabolic products
of muscular activity, but also to transport heat away
from the exercising muscle and to enable it to be dissipated without the core temperature of the athlete rising to dangerous levels. In many forms of endurance
exercise, particularly in hot conditions, a significant
part of the cardiac output is involved in heat dissipation with blood being shunted through the superficial
layers of the skin to dissipate this heat. This part of the
cardiac output is therefore not available for the transport of oxygen to the exercising muscle; thus, performance is limited. If, because of a raised haematocrit
from blood doping, a smaller proportion of the total
cardiac output can supply the same amount of oxygen
to exercising muscle, this releases a larger component
of the output for this secondary role of heat dissipation
which can therefore be more efficient and will allow a
higher work rate in unfavourable environmental conditions. Studies by Sawka et al. on exercise in a hot
environment suggest that infusion of 900 ml of autologous freeze-preserved blood confers considerable
advantages in terms of thermoregulation during endurance exercise"
Oh my oh my