Swimming and health

Today more than ever, when so many people swim for pleasure and exercise, it is vitally important to teach people to swim properly and to understand basic principles of water survival, for their own safety as well as the safety of others. These days many of us also engage in recreational activities associated with the sea, lakes or rivers, such as sailing, canoeing and windsurfing, where the ability to participate is overridden by the necessity of being able to swim. But swimming is not just a means of survival. It has long been regarded as the best overall means of symmetri-cal and systematic body exercise and now the scien-tific evidence exists to prove the point. As a sport and energetic pastime, swimming was much acclaimed by the early civilizations. During the Middle Ages, however, the popularity of swimming went into a decline as the great plagues and epidemics swept across Europe. Extraordinary as it may seem to us now, it was believed then that water and bathing were responsible for much of the illness. The increased knowledge of, and interest in, public health in the late nineteenth century, including discovery that diseases such as cholera, were in fact transmitted through contaminated water and could therefore be controlled by purifying the water supply made swimming and bathing much safer. Swimming was introduced to the Olympic Games in 1896 and since then there have been countless ‘learn to swim’ campaigns to teach more people the skill. These came into prominence during the World War II, when it became necessary to teach many thousands of servicemen to swim since the sea was a significant theatre of operations.

Bodily effects

The human body has natural buoyancy but some of us float lower in the water than others, because body density varies. The body itself does not floot horizon-tally in the water because the lower half (mainly muscle and bone) is more dense than the upper half (containing the lungs and digestive fluids). The propulsion in swimming comes from the thrust of leg movements and the pulling action of arm movements. As we swim faster our bodies rise a little way out of the water, just like a speedboat or hydro-foil. As speed increases we are affected by drag, in just the same way as any boat; the drag increases with the square of the speed, so that the fastest swimming speed is soon reached.

Scientific study of swimming

In the last ten years scientists have made considerable progress in measuring the performance of swimmers, using the water sport’s equivalent of a treadmill – a machine called a swimming flume. This is simply a tank in which the subject swims in a static position, but it is possible to make the water move past the swimmer at varying speeds. In this way it is possible to attach the leads of various items of monitoring equipment, such as an electrocardiograph (ECG), to the body without impeding the swimming action. Studies carried out in Sweden using this approach have confirmed many of our beliefs about swimming. The loading on skeletal joints is slight during activities in water compared to activities on land, since gravity is replaced by water buoyancy and normal loading factors almost disappear. For untrained people, the demands on the heart and lungs during ‘average’ swimming are about the same as would be achieved through fast walking – only the body does not suffer the same aches and pains in the joints. This means that swimming is an excellent recreational sport for older people whose joints have stiffened with age. For the same reasons swimming is excellent therapy for disabled people because the loading on the limbs is considerably less than on land. Swimming and water sports are also a good form of exercise for asthmatics, especially in indoor heated pools where the warm, water-saturated air is unlikely to trigger a wheezing attack.

But people with heart conditions should consult their doctors before taking up regular swimming since blood pressure rises far more in this activity than it does in running.

Swimming as a sport

Compared to other sports the energy demands in swimming vary in a more complex manner. The individual’s usage of body fuel depends on the amount of training he or she has had, and the stroke style employed. The style is extremely important because of the effect of drag. Swedish studies have shown that freestyle (crawl) is by far the most efficient form of swimming. A trained swimmer moving at a speed of 0.6 metres per second used less than half the energy of an untrained swimmer moving at the same speed. One major problem that ‘land’ athletes have is dissipating heat. Top-class runners’ bodies have to devote a considerable amount of their circulation to this, by pumping blood to the skin so that it loses heat to the surrounding air – this is illustrated by the well-known red face that develops when we exert ourselves. Extra blood in the skin, however, means less blood is available to go to the muscles. For the swimmer this ‘cooling factor’ is more easily dealt with because of the cooling effect of water, and therefore less blood needs to circulate in the skin, leaving more – with more oxygen, therefore – available to assist muscular activity. However swimming in cold water for a prolonged period, as we all know, can cause a severe drop in body temperature (hypothermia) which can be dangerous.

The benefits of swimming

The benefits of swimming more than outweigh the dangers – provided one can swim competently.

Although all of us have natural buoyancy, and theoretically should be able to swim if thrown into water, swimming is usually an acquired skill. In several countries children learn swimming at school.Many older people are unable to swim because they have developed a fear of water and when they try their bodies become tense, stiff and uncoordinated, which in fact have the effect of making the perfect preconditions for drowning.

It is now accepted that the best age to learn to swim is when still a baby, since water is not perceived as a danger. Babies are born with several reflexes that aid survival in the water (they cease breathing temporar-ily when submerged, for example) but if these reflexes are not exercised regularly they soon fade.


A commonsense attitude to water sports, such as swimming where it is safe, and not swimming to the point of exhaustion, should prevent the swimmer from getting into trouble.

Dealing with a person in difficulties can be hazardous: do not attempt to rescue someone by swimming to them if you are not trained in life-saving techniques. Once a victim of drowning is ashore, the important steps are to keep him or her breathing, using an approved resuscitation method, and to keep them warm until trained help arrives. Do not attempt to empty the lungs of water since there will be very little in them – the airways go into spasm if water trickles in, to prevent further fluid intake.

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