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NAUI Master Scuba Diver 138 Diving Physiology heating. Men generally need to dissipate heat more than women, since they usually generate more heat than women. In warm conditions, it is difficult to dissipate heat, and men, particularly large men, often overheat. In marathon runs and bike races, males outnumber females in cases of heatstroke, even when corrected for relative numbers competing. Dehydration. Men lose a higher percentage of their body weight in sweat while working in the heat than women. Because men usually have a higher water requirement, men seem to have a higher risk of dehydration and electrolyte loss than women when working in the heat. Chilling. Women are not at higher risk of chilling or hypothermia than men, as popularly thought. Women’s bodies are highly developed for survival, and while they often generate less body heat than men for the same work load, women are efficient at limiting heat loss. Women seem more willing and likely to get out of the water when they are cold, which can indicate that they are more cold than their male buddy, or that the male buddy is at greater risk of chilling because he has not gotten out of the cold. Regarding statements that women’s surface-to-mass ratio makes them more susceptible to chilling, it doesn’t. There is far more to chilling than this ratio. The ratio is not determined by gender, and any woman or man may have a larger or smaller ratio. The ratio does play a small role determining heat loss in extremely short people, such as children, compared to adults. The ratio also is important in body structures having a large ratio, such as fingers and ears, which is one of the reasons why fingers and ears sometimes chill easily. The statement that women’s curves increase their ratio and increase risk of chilling neglects the fact that both men and women have curves as part of every normal structure. It could be argued that men’s muscles constitute more curves than women. Men’s genitals are curves that, like fingers and ears, have a high enough surface-area-to-mass ratio to be at high risk in the cold. “Frostbite shorts” under various names, is a real and not uncommon danger to men in the cold. Implants. Implants of silicone and other materials are used to reconstruct the breast or testicle after cancer surgery, and penile implants are used to treat impotency. Chins, chest, and other sites are cosmetically augmented in both men and women. There was early speculation that gas absorption in these implants may pose a risk, but this has not been shown to be the case. Remember also, in the case of chest implants, whether for breast augmentation or for bodybuilders to simulate muscle, that your chest tissues move and expand far more during ordinary breathing than would be possible through gas expansion. Stories of spectacular rupture are just that - stories. Birth Control. In the past, there was speculation that since some forms of birth control pills were related to certain problems with some women’s circulation, these pills might have relation to increased susceptibility to DCS. This has never been shown to be valid. Pregnancy. The common recommendation in the United States is not to scuba dive during pregnancy. Diving during pregnancy is not unusual in Europe. Reports indicate no higher rate of birth defects than normally occur. Regarding maternal safety, the death rate from pregnancy and childbirth alone is 3-8 per 100,000 in Western countries, higher after age 35. In developing countries, one in four women dies or is disabled by pregnancy or childbirth. Scuba diving is far safer than being pregnant. Pregnancy is not considered a contraindication to hyperbaric treatment for carbon monoxide poisoning. The hyperbaric environment was not found to produce birth defects. Ruling out diving during pregnancy is not based on known facts, but rather on what is not known about the issue. The statement is often considered a legal necessity. Menstruation. If you feel well, go ahead and dive. The cool water and physical exercise help relieve symptoms. Concerning published statements that PMS enhances tendency to hostility and “difficulties” with buddies, there is quantitatively no more of a tendency than inherent in a given male at any point during the month. It may be safe to say that tendency to aggression or altercation may be more representative of the male than female. Menstrual blood does not attract sharks. Neither does it attract grizzly bears during camping trips, or cause wings to fall off airplanes, as pilots insisted in the 1920s.


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