There are a number causes of cramping while swimming, and basically they are the same ones that cause cramping with most other sports and forms of exercise: electrolyte loss, conditioning and unnecessary tension. The most common of these when it comes to swimming is unnecessary tension. Unnecessary tension, like plantar flexing, is an involuntary action that is unnatural. The body will attempt to correct this unnatural position, causing a cramp.
Another contributor is a reduced blood flow in the legs. The horizontal position, a lack of engagement of the primary muscles and cold can reduce flow leading to cramp. Cold will cause blood to flow to the skin surface for heating, away from the leg muscles.
There is generally not one solution to swim cramping and a holistic approach needs to be taken.
Three preventative actions:
- Ensure good nutrition, everyday nutrients and pre-swim hydration
- Always kick, using at least a two beat flutter kick, even in a wetsuit.
- Although plantar flexing maximises propulsion, holding this position is un-natural for extended periods. This is not familiar if all training is in the pool as it is relieved every turn. More open water swims would help conditioning, alternatively flex the ankle every few minutes, even if it does slow you a little.