Most of the times (86%), no CIVD of any kind (defined in that study as a 1°C rise in skin temperature) was observed in the toes, and the number of CIVD occurrences did not increase during the training. Also, the toe temperature

at the end of the immersion period did not change over the 15 days. Table 1 shows an overview of the main field and laboratory studies previously discussed. In surveying laboratory-based attempts at eliciting cold adaptations in the extremities, only one laboratory acclimation study reported clear evidence of CIVD trainability across a number Y27632 of parameters [1]. Two other studies demonstrated moderate levels of trainability with higher peripheral temperatures [35,66], whereas Yoshimura [75] found some evidence for trainability in youngsters only. In contrast, many studies found no effect of repeated immersions [22,36,37,59,65]. Furthermore, three studies observed Anti-infection Compound Library in vivo a decrease in CIVD response after repeated cold exposure [18,34,55] and concluded that the extremities may actually be at a greater risk after training. Overall, although the general

trend is for no laboratory-based acclimation, it remains difficult to account for the disparate and contradictory findings across studies. It can be argued that the nonsignificant reports resulted from an acclimation protocol that was inadequate in intensity, duration, or frequency of cold exposure. Four daily immersions of the index finger in ice PtdIns(3,4)P2 water for a month elicited faster onset of CIVD and a decrease in pain in the index finger compared with nontrained digits [1]. In contrast, in most recent studies, the subjects immersed their extremity only once every day, whereas older studies performed six immersions daily [22,37]. Few studies can logistically replicate the four 20-minute daily immersions over a month performed by Adams and Smith [1], and such an intensive protocol may not be practical to implement. More importantly, a prolonged laboratory acclimation regimen does not appear to guarantee

thermal adaptations in the extremities, as the most extensive protocol achieved to date, that of six daily immersions for 125 days, observed no trainability in thermal responses [22]. Variability in water temperature and depth of immersion can also potentially influence the presence or magnitude of thermal adaptation. A larger cooled surface area may relate to a greater cold stimulus, and thus increase trainability. Conversely, from previous studies of Sendowski et al. [68], it is proposed that deeper immersion also causes cooling of the supplying blood vessels and thus may inhibit CIVD magnitude. Current data from trainability studies favor the former perspective, as Reynolds et al. [65] reported no thermal adaptations with foot immersion, whereas Savourey et al. [66] immersed the leg up to the knee in cold water and elicited higher foot temperatures after acclimation.