Five weeks of intermittent hand exposures to alternating cold and hot stimuli do not modify finger cold-induced vasodilatation response

We tested the hypothesis that prolonged intermittent hand exposures to transient contrast thermal stimuli would enhance the finger cold-induced vasodilatation (CIVD) response during localized cooling. Eight healthy men participated in a 5-week regimen, during which they immersed, thrice per week, the non-dominant (EXP) hand in 8° and 43 °C water, sequentially and at 3-min intervals, for a total period of 60 min. The contralateral (i.e., dominant) hand served as the control (CON) hand. Before and after the regimen, subjects conducted two 30-min hand cold (8 °C water) provocation trials, one with the EXP hand and the other with the CON hand. In addition, a flow-mediated dilatation test was performed in the brachial artery of the EXP arm. Regardless of the hand tested, the average finger skin temperature [CON hand: pre-trial = 10.5 (1.2)°C, post-trial = 10.8 (1.3)°C and EXP hand: pre-trial = 10.7 (1.1)°C, post-trial 10.9 (1.1)°C; p = 0.79], and the incidence of CIVD events [CON hand: pre-trial = 1.1 (1.2) events, post-trial = 1.2 (1.1) events and EXP hand: pre-trial = 1.1 (0.8) events, post-trial = 1.1 (0.8) events; p = 0.88] were not affected by the 5-week regimen. The sensation of cold-induced pain was transiently alleviated following the regimen (p = 0.02). The flow-mediated dilatation response of the EXP brachial artery remained unaltered [pre-trial = 5.4 (3.2)%, post-trial = 4.7 (3.6)%; p = 0.51]. Therefore, five weeks of intermittent hand exposures to alternating cold and hot stimuli do not improve finger temperature responsiveness to sustained localized cold.