Effect of the Forearm Tissue

Recent work suggests an influence of the mean body skin (Tsk) and deep body temperatures (Tb) on coldinduced vasodilatation (CIVD). For example, minimum finger temperature (Tfi,min)was lower, and the maximum finger temperature (Tfi,max) was greater during CIVD when Tb was elevated, and the onset time of the CIVD response was reduced at higher Tsk. Question remain, though, about the influence of forearm tissue temperature on CIVD at a given Tsk and Tb. On two different occasions, eleven healthy male subjects pre-conditioned their forearm tissue at two different water temperatures (Tw), 20 and 38°C, until steady state forearm muscle temperature was achieved. After the conditioning period (129 ± 15 and 85 ± 15 min for 20 and 38°C, respectively), the fingers of the conditioned forearm were immersed in a 5°C water bath for 30 min. During finger immersion, Tsk and Tb were similar at each forearm skin temperature (Tsk = 34.3 ± 0.6°C, Tb = 36.8 ± 0.2°C), but temperature 3cm deep into the forearm’s flexor digitorum profundus muscle differed significantly, averaging 23.6 ± 1.7°C when Tw was 20oC and 36.7 ± 0.6°C when Tw was 38°C. Arterial blood temperature in the radial artery measured at the wrist averaged 28.2 ± 2.5 and 35.6 ± 0.9°C for the 20 and 38°C conditions, respectively (p < 0.05). The two forearm conditions caused significant differences in all the CIVD parameters during the 30 min immersion in 5°C water. During the 38oC condition, the onset time for the CIVD was faster and the average, maximal and minimal Tfi were higher than during the 20oC condition. We concluded that a low forearm tissue temperature impedes the CIVD response despite normal Tsk and Tb, possibly by decreasing the temperature of the arterial blood to the fingers.