Cyclic intramuscular temperature fluctuations in the human forearm during cold-water immersion

The purpose of the present study was to investigate the intramuscular temperature fluctuations in the human forearm immersed in water at 15 degrees C. Tissue temperature (Tt) was continuously monitored by a calibrated multicouple probe during 3 h immersion of the forearm. The probe was implanted approximately 90 mm distal from the olecranon process along the ulnar ridge. Tt was measured every 5 mm, from the longitudinal axis of the forearm (determined from computed tomography scanning) to the skin surface. Along with Tt, rectal temperature, skin temperature and heat loss of the forearm were measured during the immersions. Five of the six subjects tested showed evidence of cyclic temperature fluctuations in the forearm limited to the muscle tissue. The first increase of the muscle temperature was observed 75 (SE 6) min after the onset of the immersion, and the duration of the cycle averaged 36 (SE 3) min. The maximum increase of the muscle temperature, which ranged between 0.4 degrees C and 1.0 degrees C, was measured at the axis of the forearm, and was inversely correlated to the circumference of the subject's forearm (P less than 0.05). No corresponding increases of the skin temperature and heat loss of the forearm were observed for the complete duration of the immersion. These data support the hypothesis of a significant contribution of the muscle vessels during cold-induced vasodilatation in the forearm.