The swimming pool is not only an environment for swimming, but an irreplaceable means to meet the most diverse needs. The activity in the pool is in fact very rich and varied. The water, thanks to its characteristics, allows you to practice a multitude of movements which, with or without the use of small tools, always have a metabolic value … So let’s see, in summary, the main peculiarities that make the element water so special:
– Resistance of the medium (R): It is the force that opposes the movement of a body immersed in a fluid and depends on the density of the latter. In practice, the body must “open” the way between the fluid molecules, rejecting them sideways as it advances. R increases with the square of the speed variation of the moving body. Thus, by doubling the speed of displacement (of the body or part of it, e.g. a limb), R quadruples. Water density is 1000 times more than air. As a consequence, the maximum speed that can be reached by man in water is low, while the energy cost is very high. It should be remembered that, at very high speeds, close to 300 km/h, R varies not with the square, but with the the cube of speed increases.
– Hydrostatic thrust, or Archimedes’ principle. It is inappropriate to say that there is no such thing as gravity in the water or that gravity is reduced. In reality, it remains unchanged. However, it is balanced by a vertical force, directed upwards, equal to the weight of the fluid displaced by the immersed body, and applied to its geometric centre.
– Hydrostatic pressure. A liquid, due to its own weight, exerts on the walls of the container containing it and on the surface of the bodies immersed in it, a pressure directly proportional to the specific weight of the liquid and the depth at which the bodies are located (Stevino’s law).
The properties described make water irreplaceable in functional rehabilitation after a traumatic event or surgery on the locomotor system. The water also allows an injured athlete to continue to train in particularly favourable conditions, thanks to the possibility of to be able to accurately scale the load on the articular structures. The percentage of body weight, in fact, is a function of how much part of the body is immersed. It goes from 80% of the earth’s weight, when standing with water at mid-thigh, to 33% with water at chest, up to 7% with water at neck.
In addition to rehabilitation, the pool is used for therapeutic purposes in many diseases:
– Obesity (using hydrostatic thrust). In slimming strategies, it is essential to increase daily physical activity and to follow a moderately low-calorie personalized diet plan, so that a negative energy balance is determined. This means metabolically “burning” more calories than food. The submaximal movement performed in water, with the same intensity of the same exercise done “dry”, determines a lower use of glycogen (the reserve sugar present in the muscles and liver) and, therefore, a higher percentage use of fats as fuel. This fact, together with the drastic reduction of the risk of muscular-articular injuries, makes swimming and the various forms of water aerobics the ideal condition to carry out important physical work, even daily.
– Deep venous insufficiency (using hydrostatic pressure). I mentioned before that, according to Stevino’s law, the water pressure increases linearly with the depth (1 atmosphere every 10 meters). With the simple vertical immersion a difference in altitude between the various body segments is determined. This determines a powerful “elastic sock” effect on the body, precisely because the pressure gradually decreases from the feet to the trunk. In practice, the blood is pushed upwards and is thus facilitated the venous return.
– Lombalgia. Immersion causes the disappearance of the automatic postural activity of the paravertebral and abdominal muscles. This, together with the water-induced myorelaxant effect, favours the reduction of analgesic contractures and therefore the reduction of lumbar pain.