Tissue temperature transients in resting contra-lateral leg muscle tissue during isolated knee extension

This study was designed to evaluate the role of non-active tissue in the retention and dissipation of heat during and following intense isolated muscle activity. Six subjects performed an incremental isotonic test (constant angular velocity, increases in force output) on a KINCOM(TM) isokinetic apparatus to determine their maximal oxygen consumption during single knee extensions ((V)over dotO(2sp)). In a subsequent session, a thin wire multi-sensor temperature probe was inserted into the left vastus medialis under ultrasound guidance at a specific internal marker The deepest temperature sensor (tip, T-mu10) was located similar to10 mm from the femur and deep femoral artery with 2 additional sensors located at 15 (T-mu25) and 30 (T-mu40) mm from the tip. Implant site was midway between and medial to a line joining the anterior superior iliac spine and base of patella. Esophageal temperature (T-es) temperature was measured as an index of core temperature. Subjects rested in a supine position for 60 min followed by 30 min of seated rest in an ambient condition of 22 degreesC. Subjects then performed 15 min of isolated single right knee extensions against a dynamic resistance on a KIN COM corresponding to 60% of (V)over dotO(2sp) at 60degrees (.) sec(-1). Exercise was followed by 60 min of seated rest. Resting T-es was 37 degreesC while T-mu10, T-mu25, and T-mu40 were 36.58, 36.55 and 36.45 degreesC, respectively. Exercise resulted in a T-es increase of 0.31 degreesC above pre-exercise resting. T-mu of the non-exercising leg increased 0.23, 0.19 and 0.09 degreesC for T-mu10, T-mu25, and T-mu40, respectively. While T-es decreased to baseline values within similar to15 min of end-exercise, T-mu10 reached resting values following similar to40 min of recovery. These results suggest that during isolated muscle activity, convective heat transfer by the blood to non-active muscle tissue may have a significant role in maintaining resting core temperature.