To increase methodological control over field studies, another option is to perform laboratory acclimation studies. The advantage of laboratory-based PF-01367338 studies is the ability to isolate individual factors that may contribute to CIVD, such as duration and intensity of local and/or whole-body thermal stress. Studies on adaptation using this approach were performed extensively in the 1950s and 1960s, remained dormant for several decades, and have received renewed interest over the first decade of this century.

The general trend of these studies suggests that laboratory acclimation is difficult to achieve without an intense and extensive protocol, and also that a greater potential for adaptation exists in the fingers compared with the toes. Research in the 1950s and 1960s reveal no clear picture of the potential trainability of the CIVD response. One of the earliest laboratory acclimation studies is that of Yoshimura and Iida [77]. Five subjects immersed their middle finger in ice water every two or four days for a month. The CIVD response hardly changed; RIF, and index integrating onset time, average finger skin temperature, and minimal finger skin temperature

during immersion of a single finger in ice water, was within 1 point (scale ranged from 3 to 9 and anchored to a norm of 6 based on a cohort of Japanese soldiers). In another Selleck KU57788 study of Yoshimura, three groups of young males (16–17 year old) and adults were exposed to either 15 minutes daily immersion of the foot in ice water, 30 minutes immersion or no immersion (control group) [75]. The authors reported that no changes occurred in the control group, but an enhanced hunting reaction was evident in the trained group, in particular the young boys. However, a closer look at the values in the Tables in [74] reveals that only the temperature response improved and not onset time of CIVD. This was followed by the acclimation study with the highest frequency, duration, and

intensity of cold exposure second by Adams and Smith [1]. Five subjects immersed their right index finger in ice water for 20 minutes, four to six times a day for a month. They observed significant improvements of the CIVD response: the cycle time decreased from 8.0 ± 0.2 minutes to 7.0 ± 0.2 minutes and the final finger temperature increased from 8.7 ± 0.5 to 12 ± 0.7°C. However, the longest acclimation protocol to date, consisting of 6 subjects immersing one finger in stirred water at 0°C six times a day for 125 consecutive days, found no differences in thermal responses between the immersed finger and contralateral, nontrained finger [22]. Recently, a revived interest in CIVD trainability has led to several controlled studies on this topic. While the variation in training regimens and CIVD quantification continues to make it difficult to compare across studies, the general trend also appears to be minimal adaptation with laboratory acclimation programs.