What happens to your body when you get in the pool?

Even before you begin to exercise, the water has an effect on your body. The hydrostatic pressure acts like a compression sleeve, reducing the stress on your heart and blood vessels. Circulation increases and blood vessels relax. That means your heart is able to pump more blood with each heart beat. Your resting heart rate slows down; so does your exercise heart rate. That is why your heart rate is lower when you exercise in the pool than when you exercise on land, even though you you are working just as hard. Your blood pressure decreases, and this effect may last for some time after you get out of the pool.

Circulation increases through all of your organs. This includes the kidneys which work more efficiently, increasing the production of urine. That is why you may have the urge to head to the locker room right after your workout. Circulation through the lungs increases too, which enables the blood vessels to deliver oxygen to the working muscles more efficiently. At the same time the water pressure against your chest strengthens the muscles you use to inhale and exhale. Circulation increases through the brain, providing nutrients that help with brain health.

Water conducts heat away from the body, When you enter an 84 degree multipurpose pool, you feel cool because the water temperature is lower than your body temperature. It doesn’t take long for most people to warm up once they start moving. With the water conducting your body heat away, you will likely feel more comfortable during your exercise session than if you were exercising on land. If you are one of those who continue to feel chilled, wearing a long sleeved top such as the ones sold by Hydro-Fit can help with that.

Buoyancy reduces your hydrostatic weight. Movement may seem easier than on land because you feel lighter. At the same time the viscosity of water requires an increase in muscular effort to move the arms and legs. There is resistance in all directions. You have a concentric muscular contraction no matter which way you move, which improves muscular fitness. The movement of water around your body acts like a massage, so most people do not experience muscle soreness after their water workout.

Buoyancy reduces stress on the joints, which helps reduce joint pain. Deep water offloads the spine, which is helpful for someone suffering from back pain. Water pressure reduces swelling, especially in the legs and ankles. Healing may occur more rapidly due to the influx of blood flow to muscles and tissues. That is one reason why athletes often rehab from an injury in the pool.

Chris Alexander

Resources: AEA Aquatic Fitness Professional Manual, 2026. Becker, and A.J. Cole, Comprehensive Aquatic Therapy. 2010.