Effect of cold-induced vasodilatation in the index finger on temperature and contractile characteristics of the first dorsal interosseus muscle during cold-water immersion.

We investigated whether cyclic elevations in index finger temperature (cold-induced vasodilatation, CIVD) during prolonged cold exposure correlated with hand temperature and neuromuscular function. Evoked twitch force of the first dorsal interosseus (FDI) muscle was measured every minute in eight males and four females [age 25.4 (5.7) years, mean (SD)] during cooling of the hand for 30 min in 9 degrees C water, and in thermoneutral 30 degrees C water. During cooling, index finger temperature increased from 9.4 (0.9) degrees C at the nadir to 13.3 (2.4) degrees C (P<0.01) at the apex of the CIVD. However, the minimum skin temperature above the FDI muscle was 14.2 (2.1) degrees C, with no CIVD detected in any of the subjects. Peak twitch force was 2.5 (0.7) N at the nadir of the finger CIVD and 2.0 (0.8) N at the apex (P=0.07), time-to-peak increased from 189 (18) ms to 227 (26) ms (P<0.01), and half relaxation time increased from 135 (14) ms to 183 (32) ms (P<0.01). We conclude that CIVD is a local phenomenon isolated to the fingers, and that it does not have beneficial effects on either temperature or neuromuscular function of the FDI muscle during cold exposure.