Firstly, the most obvious being that you are suspended in water and thus the gravitational force acting upon you is at a minimum. Hence the joints, muscles and fascia already have a slight lengthening effect induced that when mixed with gentle movement further stretches and elongates the body in a rhythmic way.
Due to the body generally being on a horizontal plane for the movement of swimming you are naturally engaging your ‘core’ regardless of the stroke you are using. I know many forms of exercise/body movement/stretching are always emphasising engaging your ‘core’, however subtle shifts of body engagement can make the BIG difference of seemingly using your core to drive the movement and actually truly engaging your core to initiate the movement. The beauty of being in water and swimming is that to maintain the horizontal plane you must truly engage your core, you cannot fake it!
Another beautiful aspect of being in water and swimming is that in order to get from point (a) to point (b) the vast majority of people follow a rhythmic pattern of breathing. It is something that occurs naturally in an individual who is doing freestyle or breast stroke to follow a rhythm and breathe every stroke to few strokes. This action of rhythmic breathing resembles certain Daoyin exercises and is a great way to engage the healing parasympathetic aspect of the autonomic nervous system.
To recap, swimming combines conditioning with stretching and is a great way to increase circulation, flexibility, strength, and synovial fluid production as well as align the spinal column. It engages rhythmic breathing and thus engages the parasympathetic nervous system, furthermore it forces one to utilise their core muscles and can provide the core conditioning lacking in certain cases of back pain. Finally it does all this without the acting pressure and stress of gravitational force.
As always please feel free to contact me with any questions.
Giancarlo Nerini - Licensed Acupuncturist