COLD ACCLIMATIZATION IN ACTIVE ANTARCTIC SCUBA DIVERS 1203

Abstract

The purpose of this investigation was to determine whether the cold exposure associated with polar scuba diving operations could result in measurable cold acclimatization in humans. Antarctic-cold-exposed (ACE) subjects (n=4; male) lived in semi-permanent structures in an isolated field camp (77°S 163°E) during the austral spring, conducting 4.9±0.6(4.3-5.9) dives per week for biological research (water -1.9°C; air -36.7 to -5.8°C). Matched bi-weekly-tested (BWT) subjects remained in the U.S. throughout the study period (autumn). Physiological responses to standardized peripheral (30 min digit immersion, 4°C water bath) and whole body (90 min air exposure, 5°C, supine, rest) cold tests were evaluated at two week intervals for six weeks. Analysis of variance (Group × Trial × Time) indicated significant but subtle Group × Trial interactions(p<0.05) in mean digit temperature during the peripheral tests and in mean rectal and mean skin temperatures and mean heart rate during the whole body tests (accounting for 16.4, 8.0, 1.5 and 7.7% of dependent score variability[eta squared], respectively). From the first to fourth trial, the ACE group demonstrated decreased mean digit and rectal temperatures, increased mean skin temperature and decreased mean heart rate (-0.83, -0.16 and +0.36°C and-6.0 bpm, respectively). The BWT group demonstrated increased digit, rectal and mean skin temperatures and heart rate (+0.53, +0.25 and +0.64°C and+5.5 bpm). ACE group changes in digit and rectal temperature and heart rate are consistent with hypothermic adaptation. The elevated mean skin temperature may indicate a concomitant attenuation of the vasoconstrictive responses. BWT group changes are consistent with metabolic adaptation, potentially induced by a combination of the cold testing and naturally occurring seasonal acclimatization. Given the modest changes, it is unclear whether the cold adaptation demonstrated by the divers working under polar conditions has any operational importance.