Temperature changes in deep muscles of humans during upper and lower extremity exercise

Objective: To examine the effect of 15 minutes of upper and lower extremity exercise on raising intramuscular temperature in the triceps surae to 39 degrees C to 45 degrees C (the therapeutic range). Design and Setting: Intramuscular temperature was measured 5 cm deep in the triceps surae using a 23-gauge thermistor needle microprobe connected to a monitor. Each subject was tested under 3 conditions: 15 minutes of rest, 15 minutes of jogging on a treadmill, and 15 minutes of hand-pedaling an upper-body ergometer. Exercise bouts were performed at 70% of each subject's maximum heart rate. Subjects: Six males, either sedentary or recreational athletes (age = 21.3 +/- 2.9 years; ht = 176.8 +/- 6.0 cm; wt = 72.7 +/- 11.6 kg; resting heart rate = 57.8 +/- 6.74 bpm; target heart rate = 156.5 +/- 3.0 bpm), volunteered to participate in this experiment. Measurements: Intramuscular temperature was measured at a depth of 5 cm before and after each test condition. Results: Data analyses consisted of analyses of variance with repeated measures and a Tukey post hoc test (P <.05). The results showed a significant temperature increase over baseline after exercise on the treadmill (2.2 degrees C +/- 0.63 degrees C); however, it did not yield temperature increases greater than or equal to 39 degrees C. No significant temperature change occurred after exercise on the upper-body ergometer (-0.45 degrees C +/- 0.80 degrees C). Conclusions: Active exercise increased intramuscular temperature in working muscles but did not affect intramuscular temperature in nonworking muscles. In addition, 15 minutes of jogging on a treadmill at 70% of maximum heart rate was not sufficient to raise intramuscular temperature to 39 degrees C to 45 degrees C.