As you get tired, your muscle’s reflex control becomes dysfunctional. Instead of contracting and relaxing like they’re supposed to, they keep firing. Basically, your muscles become “twitchy” and can’t stop contracting.
This theory is supported by several lines of evidence.
1. The muscles you use the most during your workouts are the ones that usually cramp.
2. Muscles that cross multiple joints are more likely to cramp than other muscles. These muscles generally have more activity during exercise when they’re more likely to get tired.
3. You’re far more likely to cramp during a race than you are in training — when you’re pushing yourself harder than normal. Cramps also tend to occur at the end of races when you’re most fatigued.
4. If you don’t pace yourself properly, you’re more likely to cramp. Athletes who go out too hard relative to their training experience are much more likely to cramp than those who stay within their limits.7,14
5. Drinking pickle juice helps cramps disappear faster than drinking water or nothing at all, and this happens before the salt from the pickle juice can be absorbed. Researchers think this is because the salty taste of the pickle juice “tricks” the brain into relaxing the muscles.12
6. Some evidence indicates that athletes who cramp have more muscle damage before races.