Every type of exercise has its selling points. But swimming is unlike any other aerobic workout in a few important ways.
First, the fact that you’re submerged in water means your bones and muscles are somewhat unshackled from the constraints of gravity, says Hirofumi Tanaka, a professor of kinesiology and director of the Cardiovascular Aging Research Lab at the University of Texas.
This makes swimming the ideal exercise for people with osteoarthritis, for whom weight-bearing exercise can be excruciatingly painful. According to Tanaka’s research of people with the condition, swimming decreases arterial stiffness, a risk factor for heart trouble. More of his research has linked swim training with lower blood pressure among people with hypertension. The coolness and buoyancy of water are also appealing to people who are overweight or obese, for whom load-bearing aerobic exercises like running may be too hot or uncomfortable, Tanaka says.
But don’t be fooled; your body is working hard when you’re in the pool. Water is denser than air, so moving through H2O puts more external pressure on your limbs than out-of-water training, studies have shown. Even better, that pressure is uniformly distributed. It doesn’t collect in your knees, hips or the other places that bear most of the burden when you exercise with gravity sitting on your shoulders.