Exercise-associated muscle cramps have a variety of causes, with sodium loss and muscle fatigue topping the list. Since I've already covered muscle cramps from sodium loss in a previous post, I want to cover the muscle fatigue theory.
The muscle fatigue theory states that when a muscle is pushed beyond it's capacity during exercise, it will become over-stimulated, resulting in excessive muscle contraction. A cramp is sustained muscle contraction. I like this theory for a variety of reasons, with the first being that it is easy to train muscles that are fatiguing easily. Second, there are other problems that lead to muscle fatigue that are easily fixed.
Frquently, muscles fatigue when they are working harder than their neightboring muscle groups. Some of the culprits include the Anterior Tibialis in the front outside part of the calf, the calf muscles, gluteus medius and minimus (smaller butt muscles), and the muscles of the hands and feet. If you are getting any cramps and/or pain in these areas, you might be suffering from muscle fatigue.
These are hard working muscle groups. The anterior tibialis has been considered the culprit for shin splints for years. This muscle does double duty during running for both lifting the toes off the ground and slowing down the lower leg so that you can keep up with your legs. This slowing down, or deceleration, puts a lot of strain on the muscle and may be responsible for other problems as well.
The muscles in the hands and feet are small, yet important and are more likely to cramp during swimming.
The small hip muscles of the butt play a role in stabilizing the pelvis and can cramp during almost any sport.
The calf muscles are also likely to cramp when trying to keep up with the bigger muscle groups of the legs: the quads, the hamstrings and the gluteus maximus.
Smaller muscles fatigue not only from poor posture and core strength, but also from intense exercise. One of the most frequent symptoms for latent exercise asthma is also muscle cramps (the smaller muscle groups are the first to pay for decreased oxygen delivery).
Cramps are not just a fluid/electrolyte disorder and may have an underlying problem that, once diagnosed, is easily fixed.