Effect of exercise intensity on tissue temperature transients during and following exercise

We examined the effect of exercise intensity on core and active and non‐active muscle tissue temperature transients during and following exercise. Six male subjects performed an incremental isotonic test on a Kin‐Com isokinetic apparatus to determine their maximal oxygen consumption during bilateral knee extensions (Vo 2sp ). On separate days, subjects performed 15 min of isolated bilateral knee extensions at a moderate (60%VO 2 sp) (MEI) and high (80%VO 2 sp) (HIE) intensity exercise on a Kin‐Com, followed by 60 min of recovery. Muscle temperature was measured using a temperature probe inserted in the vastus medialis (T VL , 5.8 cm deep) and triceps brachii (T TB , 3.7 cm deep) muscles by ultrasound guidance. Baseline T es , T VL , and T TB were similar between conditions (i.e., 36.72, 36.18 and 35.14°C respectively for MEI and 36.74, 36.14 and 35.29°C respectively for HIE). Exercise resulted in a T es increase of 0.51 and 0.91°C for MEI and HIE respectively. Muscle temperature increased by 1.98 and 0.34°C for T VL and T TB respectively for MEI and 2.55 and 0.75°C for T VL and T TB respectively for HIE. All temperatures decreased rapidly in the initial 15 minutes of recovery. A reduced rate of temperature change was recorded for the duration of exercise with end‐recovery T es equal to 36.91 and 37.04°C for MEI and HIE respectively. Muscle temperatures remained elevated above resting values (0.89 and 0.30°C for T VL and T TB respectively for MEI and 1.08 and 0.48°C for T VL and T TB respectively for HEI). These results suggest that the transfer of residual heat from previously active musculature may contribute to the sustained elevation in postexercise T es . Funded by Natural Sciences and Engineering Research Council of Canada.