CHANGES IN INSULATION OF BODY TISSUE AND WET SUITS DURING UNDERWATER EXERCISE AT VARIOUS ATMOSPHERIC PRESSURES

To clarify the independent changes of insulations of body tissues (I(tissue)) and wet suit (I(suit)) in the wet-suited subject during underwater exercise, overall heat flow from the skin (H(tissue)) and wet suit (H(suit)) and esophageal (T(es)), skin (T(sk)), and wet suit temperatures were measured at 1, 2, and 2.5 atmospheres absolute (ATA) at critical water temperature (T(cw)). The average T(cw) in nine wet-suited men (23-38 yr) was 22.3 ± 0.2, 26.3 ± 0.2, and 28.0 ± 0.4°C (SE) at 1, 2, and 2.5 ATA, respectively. AT T(cw) of each pressure male volunteers wearing 5-mm neoprene wet suits completed three 2-h experiments while immersed up to the neck. During one experiment the subjects remained at rest, and in the other two they exercised on an underwater ergometer at two different intensities (2 and 3 met). T(es) significantly declined (P < 0.05) over 2 h from 37.1 to 36.5°C during rest in each pressure. The 2-met exercise prevented T(es) from falling in all pressures, and the 3-met exercise elevated T(es) by 0.2-0.3°C. There was no exercise-dependent difference in I(suit), but a pressure-dependent difference was remarkable. The I(tissue) at rest was identical for all pressures; however, it progressively decreased as a function of exercise intensity. It is concluded that overall I(tissue) is entirely determined by work intensity at T(cw), but not by atmospheric pressure. On the contrary, I(suit) at T(cw) is solely dependent on the pressure, but not on the work intensity.