Muscle temperature transients before, during, and after exercise measured using an intramuscular multisensor probe

Seven subjects (1 woman) performed an incremental isotonic test on a Kin-Com isokinetic apparatus to determine their maximal oxygen consumption during bilateral knee extensions ((V) over dotO(2 sp)). A multisensor thermal probe was inserted into the left vastus medialis (middiaphysis) under ultrasound guidance. The deepest sensor ( tip) was located similar to10 mm from the femur and deep femoral artery (T-mu (10)), with additional sensors located 15 (T-mu 25) and 30 mm (T-mu 40) from the tip. Esophageal temperature (T-es) was measured as an index of core temperature. Subjects rested in an upright seated position for 60 min in an ambient condition of 22 degreesC. They then performed 15 min of isolated bilateral knee extensions (60% of (V) over dotO(2 sp)) on a Kin-Com, followed by 60 min of recovery. Resting T-es was 36.80 degreesC, whereas T-mu 10, T-mu 25, and T-mu 40 were 36.14, 35.86, and 35.01 degreesC, respectively. Exercise resulted in a T-es increase of 0.55 degreesC above preexercise resting, whereas muscle temperature of the exercising leg increased by 2.00, 2.37, and 3.20 degreesC for T-mu 10, T-mu 25, and T-mu 40, respectively. Postexercise T-es showed a rapid decrease followed by a prolonged sustained elevation similar to0.3degreesC above resting. Muscle temperature decreased gradually over the course of recovery, with values remaining significantly elevated by 0.92, 1.05, and 1.77 degreesC for T-mu 10, T-mu 25, and T-mu 40, respectively, at end of recovery ( P < 0.05). These results suggest that the transfer of residual heat from previously active musculature may contribute to the sustained elevation in postexercise T-es.