Swimming differs from most other sports in several aspects:
A horizontal body position
Swimmers are in a prone, horizontal position during performance and training.
Arms and legs both propel
Both arms and legs are actively used for propulsion.
Pressure and breathing
Being immersed in the water causes pressure on the body and affects breathing.
Force applied to moving water
Aside from starts and turns, the forces from the athlete are at all times applied to a fluid moving element (water).
Source
Fone, L., van den Tillaar, R. Effect of Different Types of Strength Training on Swimming Performance in Competitive Swimmers: A Systematic Review. Sports Med - Open 8, 19 (2022).
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