Harvard Health Letter

A sport for all seasons

Swimming has myriad physical and psychological benefits at almost any stage or state of life.

In exercise, water is our natural ally. It lightens our load, stimulates our circulation, protects us from injury, and buoys our spirits. At the same time, it exerts just enough resistance to let us know we're doing some work. For that reason, it's no surprise that swimming is one of the most popular ways to retain — or regain — physical and psychological fitness.

How water works for us

Archimedes' bathtub epiphany explains why we begin to reap benefits the moment we step into the pool. As the ancient Greek mathematician observed, the upward force on a submerged body is equal to the weight of the water the body has displaced. This force, which we know as buoyancy, makes us seem lighter in the water than on land. People whose bodies are less dense than water — usually because they have a relatively high proportion of fat to muscle and bone — will stay afloat with little effort required.

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