Do you ever wonder why we float? or why exercise in water is so much different than on land? The unique properties of aquatic environments offer an ideal setting for health, wellness and recreation. These are the properties that make it unique:
Viscosity and Resistance. Limb movement in water is subject to a drag force and turbulence. The resistance created by the viscosity of water offers opportunities for strength training via the principle of loading (Swimming and Health Commission (SHC), 2017). In a pool, resistance is evenly distributed over the entire body, incorporating most of the major muscle groups during exercise. Resistance is 12–14 times greater in water than on land (United States Water Fitness association (USWFA), n.d).
Density and Buoyancy. The human body density is slightly less than that of water; therefore the volume of water displaced weighs more than the immersed body resulting in an upward force equal to the water displaced according to the SHC (2017). This upward force is known as buoyancy, and occurs when a fluid exerts a force on an object that is less dense than the fluid. Buoyancy allows for floating in water. Immersion of the body up to the chest (xyphoid) offloads bodyweight by 60% or more, to the neck (C7) by 75% or more (SHC, 2017). Buoyancy results in offloading of peripheral and spinal joints resulting in less stress on bones, joints, and connective tissues, allowing individuals with joint issues to tolerate longer and higher intensity exercise in water than on land. This allows individuals with injuries, painful joint conditions, balance issues or weakness, to exercise and move through a full range of motion, in a safe and enjoyable manner.
Hydrostatic Pressure. Pressure is produced by the weight of a fluid, and acts on the body. The amount of pressure on the body increases as depth increases. The hydrostatic pressure results in a shift of blood towards the heart, raising right atrial pressure, and causes displacement of the diaphragm towards the head (caudally) (SHC, 2017).
Body Temperature and Thermodynamics. Water may be used over a wide range of temperatures due to its heat capacity and conduction properties. This allows the temperature to increase and create a therapeutic environment, which is a safe and comfortable for exercise (SHC, 2017). Individuals engaging in water-based exercise are less likely to overheat because the water disperses heat more efficiently than air (USWFA, n.d). This enables aerobic exercise in hot summer months and encourages participation among individuals who may be unable or unwilling to exercise in the heat due to health conditions or personal preference.
Swimming and Health Commission (2017). The health and wellbeing benefits of swimming. Retrieved from: https://www.swimming.org/swimengland/new-report-shows-health- benefits- swimming
United States Water Fitness Association (n.d).