Exercise-associated muscle cramps


As a masters squad swimmer, I have found myself and many of my fellow squad swimmers suffer from painful leg and foot cramps towards the end of a training session. Exercise-associated muscle cramps (EAMC) are painful and disruptive for those who experience them, and can become debilitating if they occur regularly.  

Cramping during exercise is very common, cramping is more likely to occur when muscles are in a shortened and contracted state. But why do they occur and what triggers them? 

What causes Exercise-associated muscle cramps?

Everyone has an opinion on this - increasing fluid intake; taking magnesium tablets, and eating potassium rich foods are just a few of the theories. Despite their commonality and prevalence, their cause remains unknown. (1) 
A study on EAMC by Kevin C. Miller et. al in the Sports Health journal found: 

Because EAMC occur in a variety of situations, environmental conditions, and populations, it is unlikely that a single factor (eg, dehydration, electrolyte imbalance, or neuromuscular factors) is responsible for causing them directly. It is more likely that EAMC are due to a combination of factors that simultaneously occur under specific physiological circumstances in each athlete. (2) 

Treatment for Exercise-associated muscle cramps

Due to the lack of scientific evidence on the exact cause of EAMC it is difficult to suggest one treatment over another. There is a lack of evidence on treatments for EAMC, the one treatment which has proven to be effective from other treatments is moderate stretching of the affected muscle. (3) Evidence regarding ingesting fluids containing electrolytes, is also lacking. Absorption of electrolytes after ingestion is not immediate, and many sports drinks do not contain an adequate amount of electrolytes to replace those which the body loses during exercise. There is no harm in adding this to your post training/competition recovery as it may assist in avoiding further cramping for you. 

Prevention of Exercise-associated muscle cramps

This is something my fellow swimmers would like the answer to! In a desperate attempt to not have to throw away the fins and stop evening training sessions, the following recommendations may be of help. 

Despite the lack of evidence on the dehydration-electrolyte theory, Bye A, Kan A. found: 

An athlete who ingests a litre of water or hypotonic sports drink at least 1 hour before competition can be confident that the majority of the fluid, electrolytes, and nutrients have been absorbed and are available in the body. Fluids should be available and easily accessible throughout practices and competitions. A balanced diet is important given that much of fluid and electrolyte replacement occurs during meals. (4) 

An additional theory on the cause of EAMC is muscle fatigue, this may explain why some athletes cramp at the end of a training session while others don't. Each athlete has their own fatigue threshold. When a muscle is extremely tired, mechanisms within the muscle start to misfire. Small nerves that should keep the muscle from over-contracting malfunction, causing the muscle to bunch up rather than relax. (5). To prevent muscle fatigue endurance training and plyometric exercises may be effective in preventing EAMC. (6). 

In summary, Exercise-associated muscle cramps are not nice for anyone. If you suffer from them, and they're disrupting your training and competition, it would be worth ensuring you are: 1. Well hydrated before training and competitions (as well as in your day to day routine); 2. Well rested and not fatigued prior to training/competition; 3. You do an adequate warm-up and cool down which includes moderate stretching.



1,2,3,6. Kevin C. Miller, PhD, ATC, CSCS,*† Marcus S. Stone, PhD, ATC,‡ Kellie C. Huxel, PhD, ATC,§ and  Jeffrey E. Edwards, PhD‖ Exercise-Associated Muscle Cramps; Causes, Treatment, and Prevention Sports Health. 2010 Jul; 2(4): 279–283. doi:  10.1177/1941738109357299

4. Bye A, Kan A. Cramps following exercise. Aust Paediatr J. 1988;24:258-259  [PubMed]

5. JILL CASTLE, MS, RDN; 10/15/2013; PLAGUED BY MUSCLE CRAMPS? http://www.usaswimming.org