What causes muscle cramps in exercise?

What causes muscle cramps in exercise?


The answer to this question is actually ……we aren’t sure.  The research is relatively uncertain as to the cause.  There are two theories.  One theory is the it results from muscle dehydration and or electrolyte depletion with exercise.  The more recent theory is that it results from muscle fatigue and altered neuromuscular control creating the cramp.  It is likely that it is a combination of both.


The theory with dehydration and electrolyte depletion is that with exercise and sweating, an imbalance develops in muscles that results in:

  • Accumulation of waste products that interfere with muscle or more specifically muscle relaxation.
  • Electrolyte depletion resulting in cramp creation.
  • Loss of fluid volume within the muscle with prolonged exercise that alters the contraction of the muscle.
  • Extreme heat or cold, that results in dehydration and electrolyte imbalances and the resulting muscle cramp.


The controversy with this theory is that some studies have shown the athletes who are properly hydrated still develop muscle cramps.  However further research has shown that accurate rehydration and electrolyte replacement during and after activity increased the duration of exercise tolerated before cramping occurred.


The second theory of muscle cramping is the muscle fatigue and altered neuromuscular control theory.   Neuromuscular control can be defined as “how the nervous system (brain, spinal cord, nerves) controls the muscle. “The theory is based on the concept that fatigue alters the neurological firing sequence of the muscle resulting in cramps.

A muscle’s tone (how contracted or relaxed it is) is controlled by a spinal reflex.  Receptors in the muscles provide feedback that increases the muscle activity (muscle spindle) or decreases the muscles activity (Golgi tendon organs). The two receptors work in partnership to contract or relax the muscle during exercise.  Research suggest that fatigue causes these receptors to become imbalanced resulting in a cramp. (prolonged contraction). There is some evidence of genetic predisposition can contribute to this problem of cramping as well as poor training before exercise to tolerate the load of competition.


It should be noted that some medications have the side effect of muscle cramping, so if you experience cramping after taking a medication you should consult with your physician or pharmacist.


How can you prevent muscle cramping?

  • Exercise Nutrition – Consuming a sports drink that contains water as well as essential carbohydrates and electrolytes significantly reduces the risk of muscle cramping. This is very important if the athlete sweats profusely.  This hydration needs to increase when training in extreme heat or cold environments.
  • Appropriate training to handle the loads of competitions for the duration of the competition. (e.g.  Training at full pace for full length of a 10 km race, prior to the actually race.)
  • Dress appropriately to manage heat related fluid loss. (e.g. Layers and not too much overheating)
  • Recovery between heavy training to allow your muscles to recover physiologically.
  • Dynamic warm-ups to prepare your body for the physical activity.



What to do if you experience a cramp while exercising?

  • Stretch – by holding the stretch for a prolonged period you are stimulating the Golgi Tendon organs to cause the muscle spindles to relax the contraction.
  • Trigger point massage in the cramp area often will help release the cramp. Press and hold your thumb in the contracting muscle for 20-30 seconds.
  • Easy walking or free spinning on a bike will often help reduce the cramp, giving the muscle time to recover.
  • If the muscle continues to be sore after the cramp has resolved, you may have damaged some muscle fibres. You made need to rest for a day or two, or see a health care professional if the pain continues to get further rehabilitation.