This summer, people will flock to lakes, oceans, rivers and “concrete ponds” for the express purpose of plunging themselves into the water and flailing around madly. It’s called swimming, and it’s pretty strange behavior, considering the human body is not at all designed for water locomotion.
Nevertheless, it’s been going on for a very long time. There’s an Egyptian hieroglyph for swimming from 2,500 B.C., and the ancient Greeks and Romans held swimming in high esteem. Swimming competitions were held in Japan as early as the first century B.C.
During the Middle Ages in Europe, however, swimming declined in popularity because it was thought that water was contaminated and a source of disease–not an entirely erroneous opinion, considering the prevailing methods of sewage disposal. That attitude wasn’t dispelled until the 19th century, when swimming began to be appreciated again as a means of saving lives as well as a good form of exercise. Today, it’s popular both as recreation and as a competitive sport.
The human body is two-thirds water, and therefore its density is very close to that of water. This gives us a kind of neutral buoyancy: we float, but only when we’re almost completely submerged. This doesn’t do much to keep us from drowning.
This means part of the task of swimming is getting your head into the air for breathing. That’s what “treading water” is all about. By pushing down with the palms of the hands and kicking with the legs, you can keep your head above water. It takes a lot of energy, however. Another technique, called drownproofing, is much less strenuous and can therefore be kept up a lot longer. Drownproofing relies our natural buoyancy. Left to its own devices, the body will float, submerged, upright in the water. When you’re drownproofing, you hold your breath as long as comfortable, then gently ease your head above the water with a kick and downward push with your hands, take a breath, and relax back down into the water again. This takes very little energy.
Swimming, though, involves more than just avoiding drowning; it’s a means of self-propulsion. Most land animals, when they fall into the water, will kick their legs in the same way in which they walk or run, and achieve a certain amount of forward motion (i.e., the dog paddle). Humans, however, being intelligent, have invented a variety of strokes. All of them are based on the fact that when you push your hand through the water, the water resists. This turns your arm into a lever, with its fulcrum in the water. Applying force to the arm levers your body forward at the shoulder. (As reader Mervin L. Bailey pointed out to me recently, correcting something I said in an earlier column on boats, a boat’s oars work the same way: the oar is a lever with its fulcrum in the water, just like a crowbar dug into the ground. Because of the water’s resistance, the force applied at the upper end is transmitted to the boat as forward motion at the oarlocks.)
In the 19th century, the British still swam with their heads above the water, a holdover from the days when they believed water was a source of disease. However, in 1844 two American Indians demonstrated a more efficient method: the crawl. In the crawl, the body is chest-down. The arm is extended fully and then pulled through the water. This is the main propulsive part of the stroke: a flutter kick adds some forward thrust, but mainly helps stabilize the swimmer. The face is underwater, but turned to the side at regular intervals for breathing. The front crawl has become the basic swimming stroke.
There are three other basic strokes, the backstroke, the breaststroke and the butterfly. The backstroke is similar to the crawl but, because it is performed on the back, breathing doesn’t have to be coordinated quite so carefully.
In the breaststroke, leg and arm movements are simultaneous. The hands are extended forward from the chest, then swept back. At the same time, the legs are drawn up, with knees bent and legs turned outward, then thrust back. This is called a frog kick. Both legs and arms provide propulsion in this stroke.
The butterfly is derived from the breaststroke, but when the arms are extended, they’re brought out of the water, which lessens resistance and thus enhances efficiency. The legs remain close together and are alternately bent and straightened at the knee.
The butterfly is the most physically demanding stroke, but all swimming is fairly demanding, because of the amount of energy it takes to overcome the resistance of the water. That’s why it’s considered one of the best forms of exercise. Not only does it work all the major muscle groups, it’s not prone to causing injuries: there are no sudden shocks or pounding against hard surfaces.
Swimming does have its own dangers, however. Some people try to swim further than they’re capable of, become exhausted, and no longer have the energy to keep their heads above water. About one third of drowning deaths result such over-confidence.
Hypothermia is a constant threat in water that’s less than about 22 degrees Celsius, which includes just about every natural body of water in Saskatchewan. (Friends visiting from Texas couldn’t believe we’d swim in water as cold as that of Emma Lake, near Prince Albert…but we did.)
And then there are other hazards, such as “swimmer’s ear.” This occurs when bacteria invade the external canal that runs between the eardrum and the auricle, the visible part of the ear. Moisture in this canal, combined with the natural warm temperature, prompts the growth of common microorganisms. Exposure to water also washes away a protective acidic mantle that is normally present. The greater the exposure to water, the greater the likelihood of moisture retention in the ear canal and the greater the risk of swimmer’s ear. The solution is to make sure water in the ear evaporates; there are medications to achieve that effect, such as alcohol drops.
In shallow prairie lakes, people sometimes pick up “swimmer’s itch,” from algae that bloom in the sun-warmed, nutrient-rich waters. But at least we don’t have to worry about sea urchins and jelly-fish, painful hazards of the oceanside.
The human body may not be well-adapted to the water, but that hasn’t stopped us from enjoying it. And so, this summer, millions will once more take the plunge–and get into the swim of things.
