DR. JOLIE BOOKSPAN
This article first appeared in the
August 1992 issue of Underwater USA
Many false statements perpetuate about the ‘special considerations’ of women divers. However, there are true physiologic problems for men divers. Why no equal time? This is more than oversight, itâ€™s discrimination against men that must be addressed. Let’s give men equal time and take a look at their special needs:
MEN’S SPECIAL NEEDS
COLD: Men are not at less risk of cold injury than women, as often thought. It’s true that very small women radiate more heat than large men through something called a larger surface area to mass ratio. However, it’s a false conclusion that their risk of cold injury is therefore greater, because one isolated avenue of heat loss does not constitute global risk of injury. Women compensate for greater radiative heat loss through other heat preserving mechanisms.
Further, the surface area to mass quotient is a minor factor except when comparing extremely small people, like children, to large adults, regardless of gender. Extensive cold research in military and private sector laboratories finds no comparative threat to women’s core temperature from even extended and extreme cold exposure. Conversely, men have several disadvantages.
1. Men have less subcutaneous fat than women. Their surface layer has less insulating value.
2. A lesser known yet more important insulatory mechanism is the thickness of your ‘shell’. Your shell is the zone between skin surface and circulation. Decreases in peripheral blood flow thicken the shell. Men have high blood flow in their shell because of a lesser vasoconstrictor response to cold than women. Consequently, men have less ‘shell’ insulation.
3. Men have higher skin temperatures than women. You already know that in the cold, men are warmer to the touch than women. That’s another disadvantage. A higher gradient exists between men’s warm skin and the cold environment. That’s called a high shell to environment gradient. Heat travels along gradients from high to low – men lose more heat in the cold. An analogy is if you stand outside your house in very cold weather, touch the outside wall and find it warm, you would curse the expensive waste of heat.
Divers sometimes ask if women’s “curves” present a greater surface area for heat loss, making for a disadvantage in the cold. This is not true for several reasons. First, everyone has curves, in their various bodily structures and shapes. Body fat is a great insulator against cold. Also remember that a spherical shape has the lowest surface area to mass ratio of all shapes. However, a big problem in gender and curving structures is men’s genitals. They don’t fare well in the cold for similar reasons as fingers. ‘Frostbite Shorts’, under various names, is a documented medical malady.
Men must compensate for all this heat loss through Herculean metabolic effort. They produce more heat at high caloric cost.
CALORIC REQUIREMENTS: Men have a higher daily calorie requirement. They must be careful to eat more than women or they will suffer performance decrements. This is true in daily life where it is no more than expensive to get all the extra food, and in extreme survival conditions, where it can become a threat to survival.
The Donner Pass incident is an example. A California bound group traveled overland from Illinois in 1846. They started too close to winter and got caught in the Utah mountains. Of the 87 original members nearly half died, mostly men. There are several interrelated social, and economic reasons more men died than women, both in total numbers and by percent. But even without those, the physiologically, more men than women starved and froze to death. Bigger people and men need more food to maintain their body weight and temperature.
HIGHER RDA: Men don’t only need more calories. John Vanderveen, director of the FDA’s nutrition division stated in Time Magazine, “Young males need more nutrients than women, children, and the elderly.”
HEAT: Men’s difficulties don’t end with cold and calories. Large men are more likely to overheat than women, the reverse of common contention. Men generate much more heat than women but dissipate it less efficiently in hot weather. Their usually smaller surface area to mass ratio means they can’t radiate away as much heat as women. More troublesome, men’s higher skin temperature than women makes a smaller shell to environment gradient in hot weather. The low gradient impedes heat loss. The greatest risk is to the large, round, bull-necked men you have seen, red faced and streaming sweat in moderate heat, and have probably even seen uncomfortably hot in normal room temperatures.
DEHYDRATION: Noted thermal researcher C.H. Wyndham described men as “wasteful, prolific sweaters” in a paper in the Journal of Applied Physiology. You don’t need a research scientist to tell you that. It’s myth that men have more sweat glands than women. Men begin sweating at a lower temperature than women and, obvious to all, sweat more. However, men sweat beyond that which can be evaporated so the extra sweating confers no cooling advantage over women. Men lose more vital body fluids by volume and percent than women. Combine that with men’s higher water requirement due to their size and higher metabolic budget, and they incur higher risk of dehydration.
ELECTROLYTE IMBALANCE: Because of their high sweating rate and volume, men also risk the possibility of losing more electrolytes than women. Over long periods of time they theoretically might be at greater risk of electrolyte imbalance.
DECOMPRESSION SICKNESS (DCS): Reported incidence of DCS in men is not conclusively lower than that observed in women. Early studies showing difference compared out-of-shape women with in-shape men, and used too few women to draw any statistical certainty. Many, though not all, later studies conclude no difference in DCS risk. Studies of bubbles that are believed to cause DCS indicate no gender difference in the number, magnitude, or duration of Doppler detectable bubbles after identical dive profiles. An August 2002 paper in Space Environmental Medicine concluded that when experience and diving habits are factored, DCS rate in men was 2.6 times greater than women.
Some people theorize that DCS risk rises with body fat, leading to the unsubstantiated global conclusion that men’s risk is lower than women’s. Is that warranted? A 120 pound woman with 20% fat carries 24 pounds of fat. A 180 pound man with only 15% fat tops that with 27 pounds of fat. The three pound male margin is 12.5% more fat weight for the man. It’s not known if percentage fat or absolute fat amount is the issue.
FERTILITY: Cold water and hot water both affect male fertility. Women’s anatomy is more sensibly protected. Although thermal influence over the male was known anecdotally for centuries the seminal work in this area was conducted on pearl diving men of the South Seas. Their fertility dived after cold water excursions. Conversely, the decrease in fertility in the heat is sometimes conjectured to explain the evolution of kilts, worn by Scotsmen for two cool reasons.
AIR CONSUMPTION: Male’s lungs are bigger, using more air with every breath. Higher consumption, sometimes two times or more is documented in males, especially large males. Men are more likely to run out of air on a comparable profile than their woman buddy.
DRAG: Men are prone to streamline or ‘trim’ problems. Segmental center of gravity techniques and buoyancy analyses reveal what you already know — men carry more of their fat on their upper bodies. Their longer, heavier, leaner legs sink, causing increased drag in the water. Men’s larger upper body also contributes to their threefold back injury rate over women (see the three-part back pain series on this site for more on back pain).
SHOULD MEN BE ALLOWED TO DIVE?
Given their relatively unsuited nature to the diving environment, should men dive? Only if they want to, the same as women. Individual differences among men overshadow differences between men and women. Body size, vasoconstrictor ability, experience, height, weight, cardiovascular condition… all matter more than gender.
There is great overlap in the skills and abilities of male and female divers. So when you hear unsubstantiated global statements about women divers, set the record straight with some of men’s special considerations.