What makes water exercise easy on the body?
Buoyancy: the upward pressure exerted by fluid – in other words, the opposite of gravity. It makes us feel lighter in the water and decreases the compressive forces experienced by the joints, including those in the spine. This makes aquatic exercise a low-impact activity.
The amount of benefit provided by buoyancy for exercise depends on the depth of the water. When you stand in water that reached your belly button you reduce the impact on your joints by 50%. Since the shallowest part of our indoor pool at Legacy YMCA is over 3 feet we are always experiencing at least a 50% reduction in the impact of our joints. When you move into water that reached your arm pits, you reduce the impact by 75%. Those hearty souls that work out in water that reaches their collar bone experience a 90% reduction in impact! Moving into the deep end to perform suspended exercises removes all impact from the joints but requires a suspension belt or noodle and a high level of self-confidence. In the water the body often tilts away from the upright position. Your feet and legs may attempt to float and tip you on to your face or back. You need confidence in your ability to maintain an upright position, or recover to one.
When working out in the pool, choose a depth of water that you feel confident in.
Why is it harder for me to jog in the water than it is on land?
Water molecules stick to each other causing the resistance we call “drag”. To push through these sticky molecules, your body must exert muscular force that is 12 to 15 times greater than the force needed when moving through air. Drag helps you develop muscular fitness. It also stabilizes the body and helps it remain upright, which makes the water a safe place to exercise for people with conditions that affect balance, because if you lose your balance in the pool, you will not fall and break a bone. (But you could wind up with your head under water.)
Are there any other properties of water that effect people when they exercise?
Hydro-static Pressure: Hydro-static pressure is the pressure exerted by a fluid to an object. The hydro-static pressure of water molecules creates equal pressure on all parts of the body, and this pressure increases with the depth of the water. This characteristic of water provides great benefits for persons with swelling due to injury, edema from pregnancy, or cardiac concerns. Specifically, any edema or swelling of a joint is decreased when the joint is under water because the fluid in the joint is forced into the capillaries by the pressure of the water against the body, so the fluid returns to the bloodstream. This benefit is more noticeable in the lower limbs because they are deeper in the water where the pressure is greater. As a result, for example, pregnant women see a noticeable decrease in ankle swelling.
The hydro-static pressure of water also aids in the efficiency of the cardiovascular system, thus making the pool a popular environment for persons recovering from a cardiac incident. Because hydro-static pressure causes constriction of blood vessels, the heart is pumping blood through a smaller area; as a result, it does not have to pump as often, and the heart rate decreases. Therefore, if you monitor your heart rate while exercising in the water, you may find fewer heartbeats even if you feel you are working more intensely.