Redirection of biological heat from head to hands to support finger comfort in the cold.

ABSTRACT

INTRODUCTION: Maintaining hand comfort in the cold while sustaining optimal performance is still a challenge. There has been little research on the efficacy of transporting biological heat from the head to the hands to stabilize finger comfort, although there are notable temperature differences between these two areas in the cold. METHOD: A tubing bypass between the head and the hands was designed as an independent component in a liquid cooling/warming garment (LCWG). Seven subjects (four men, three women) were studied, comparing finger temperature (Tfing) change in two conditions LCWG with additional bypass; and LCWG without bypass. The protocol consisted of three stages 1) comfort stabilization, LCWG inlet water temperature 33 degrees C, water in loop in bypass condition 23 degrees C; 2) body cooling, LCWG inlet water temperature 20 degrees C; and 3) rewarming, LCWG inlet water temperature 45 degrees C. RESULTS: The time to reach the 25 degrees C Tfing discomfort criterion was significantly longer in the bypass condition (p < 0.01); Tfing was significantly higher at the same time point when Tfing of 25 degrees C was reached in the control condition (p < 0.01). CONCLUSION: The incorporation of a bypass transferring biological heat from a high to a low skin temperature area has potential to improve local finger comfort and thus increase the time personnel can work in cold environments.