Fig. 4.

Relationship between LVC, muscle temperature, and plasma ATP. With whole body heat stress at rest and during exercise, LVC shares a strong positive relationship with elevations in leg muscle tissue temperature and arterial plasma ATP (r² = 0.87, P = 0.001). Stepwise regression analysis revealed that the majority of the variance in LVC (87%) can be accounted for by elevations in arterial plasma ATP as opposed to the influence of muscle tissue temperature. However, elevations in muscle tissue temperature shared a strong relationship with elevations in plasma ATP (r² = 0.85 P = 0.001), which could indicate that ATP is released into the vascular system in response to elevations in local tissue temperature, thereby initiating local vasodilatation and elevations in skeletal muscle perfusion. Data for LVC and arterial plasma ATP are means ± SE for 10 subjects and 5 subjects for leg muscle tissue temperature.