The Benefits of Swimming for Health and Fitness
A new study that shows evidence of the health and well-being benefits of swimming was released earlier this summer and this Get-Fit Guy is rubbing his flippers together with glee.
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I deviated from this particular study for a few minutes to find out why BMI might be higher in a swimmer despite the fact that elite swimmers typically undertake 4000-20,000 m per day in their training, which burns thousands of calories. Two theories seem to be popular.
It has been suggested that swimming doesn't cause the appetite drop that accompanies heavy running or cycling training, so swimmers may overcompensate for the energy they have just burned. Some research goes on to suggest that this is due to the cool temperatures in which swimmers train.
Swimmers are less active outside their training sessions because they are so tired from the hours spent training that they sleep, sit or otherwise avoid any real energy expenditure outside their sessions. Which to me seems less likely that reason number one.
Also, when a sport is performed in the water, fat provides more buoyancy than muscle mass. This allows swimmers who have a higher percentage of fat to float more readily in the water. Instead of having to use energy to stay horizontal, the athlete can focus on their stroke and kick to move them forward. Swimmers with a lot of muscle mass may have more strength, but it ends up being wasted on the mechanics of trying to staying high in the water.
There does not seem to be one clear reason for this but if you watch footage from the Olympics you likely noticed that each and every sport has a particular body type, and swimming leans toward the rounded shoulders and smooth curves which are more biomechanically useful in the water than bony angles. Correlation? Causation? You choose.
Valuable Lifetime Activity
But back to the study, where the authors conclude that “swimming constitutes a valuable lifetime activity” and appears to produce healthy levels of cardiorespiratory fitness and is a viable alternative to other forms of exercise.
This is further supported by the results of a prospective study of the health effects of physical activity and fitness in 40,547 men which concluded that swimmers had lower mortality rates than those who were sedentary, walkers or runners even after controlling for age, body mass index, smoking/alcohol and family history. Similar results have been demonstrated by a cohort study of over 80,000 British adults where swimming participation was associated with a significantly reduced risk of all-cause mortality of 28%, and cardiovascular disease mortality of 41%.
Is It More Than Just Exercise?
Clearly, heading to your local pool offers a great opportunity for aerobic activity, however, the specific interaction between physiological and hydrodynamic effects of being immersed in water are also super interesting and might be lending additional advantages.
The study listed five factors that the role of water might be playing in the positive results being found.
Density - 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 volume of water displaced. You can think of this as being like a compression stocking for the part of your body that is submerged.
Hydrostatic Pressure - Pressure is proportional to the liquid density and the immersion depth (which means the deeper you go the more pressure there is). Hydrostatic pressure results in plastic deformation of the body (your body gets squeezed), shifting blood towards the heart, raising right atrial pressure, and causing a cephalad displacement of the diaphragm (cephalad means “toward the head”). You can think of this as a turbo boost which reduces the work of breathing associated with expiration, your heart’s preload, its cardiac output, and the body’s venous blood flow.
Buoyancy - Immersion to the xyphoid (a small bump of cartilage in the sternum) off loads bodyweight by 60% or more, and to to C7 (near the bottom of your cervical spine) by 75% or more. Buoyancy results in ‘off loading’ of peripheral and spinal joints. You can think of this as greatly reduced gravity and impact.
Viscosity - Limb movement in water is subject to drag force and turbulence. Viscous resistance offers opportunities for strength training via the principle of loading. You can think of this as the water being like a resistance band that’s been attached to all your limbs, turning all your movements into a strength training regime.
Thermodynamics - Water may be used over a wide range of temperatures due to its heat capacity and conduction properties. Many public pools operate at 27-29°C, although sometimes increased to 33.5-35.5°C for ‘therapeutic’ sessions. You can think of this as being like a mild icing for your sore muscles or a mild hot tub for again your sore muscles. You can find out more about cold water uses in a previous Get-Fit Guy post and you can also imagine how much harder you would be able to workout when the water is adding a cooling benefit that would usually be relegated to your perspiration and respiration.
After examining the effects of swimming on cardiovascular and cardiometabolic health, pulmonary health, musculoskeletal (MSK) health, neurological health, health for people with disability, health for the frail elderly, health for women (specifically post-menopausal women with osteoporosis, pregnant women and women with breast cancer) the study summary stated that the unique nature of the aquatic environment as a medium for exercise can layer on a large number of specific advantages, especially as compared to land-based exercise.
Which makes sense now that we see it as an exercise environment that offers reduced weight-bearing stress, higher humidity levels, decreased heat load and a greater margin of therapeutic safety in terms of falls-risk, swimming and aquatic exercise can be seen to safely and effectively meet the needs of a wide-range of individuals, in both the treatment and prevention of physical health issues.
In Chapter 2 (of the 7 chapter study), the researchers looked at very specific subsets of the population to see how swimming benefited them.