I love to swim but I am not sure if it is good on the body, do you know?
I love to swim too. Swimming is actually a low impact activity and compared to running is better on the body.
Do you work a lot of muscles? I know my body is normally tired when I am done.
Yes.  It's a great workout.  I suppose it's different for people as swimming relies on the natural buoyancy of the body.
Does it have any long term effects? Like I know running is bad on the knees long term.
only slightly less dense than water, water supports the weight of the body during swimming. As a result, swimming is “low-impact” compared to land activities such as running. The density and viscosity of water also create resistance for objects moving through the water. Swimming strokes use this resistance to create propulsion, but this same resistance also generates drag on the body.
Hydrodynamics is important to stroke technique for swimming faster, and swimmers who want to swim faster or exhaust less try to reduce the drag of the
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