The effect of deep muscle temperature on the cardiovascular responses of man to static effort.

Eight healthy male subjects (age range 24-38 year) were asked to exert a fatiguing isometric endurance contraction with their handgrip muscles at 40% of their maximum strength after immersion of their forearms in water at various temperatures ranging from 3-40 degrees C. For each subject, isometric endurance was longest after immersion of his forearm in water at a particular characteristic bath temperature; endurance decreased markedly above or below this temperature. The increase in heart rate from the beginning to the end of the fatiguing contractions was the same irrespective of the bath temperature. In contrast, the increase in blood pressure (both systolic and diastolic) throughout the contractions was almost constant for contractions exerted after immersion of the forearm in water at 20-40 degrees C, but was reduced progressively for contractions exerted in water below 20 degrees C.