WHAT IS CRAMP?
Research suggests that true cramp is ‘hyperactive, high-frequency, involuntary nerve discharges within the lower motor neurons’. This means the nerves that travel to the muscles that begin after your spinal cord, fire out messages very quickly to the associated muscle, with no voluntary control over it, causing a sudden activation of the muscle. It usually occurs in a muscle that is already slightly active.
WHAT CAUSES CRAMP?
There are multiple causes of cramp - some are more benign and others are related to other medical conditions:
Nocturnal cramps (cramps that occur at night) are often associated with reduced motor nerve endings that occur with increasing age and muscle atrophy. Damage to these lower nerves from compression in the spine or injuries can also contribute to the altered discharging of the nerves.
Cramps can occur after exercise either as a result of accumulation of waste products, dehydration and loss of key minerals used to coordinate the muscle activation such as sodium, or inadequate conditioning of the muscle for the activity in question.
It has been proposed that our modern day lifestyles with more sitting and less squatting, which is a great way to regularly stretch the leg muscles, may be related to increased cramping of leg muscles.
Certain medical conditions can also increase the chance of cramp such as neurological conditions that affect the lower nerves, hypothyroidism and kidney and liver conditions.
WHAT SHOULD I DO IF I GET CRAMP?
Cramp is the result of overactive nerve firing, so we need to switch the nerves off! The most efficient way to do this is to switch on the nerves to the opposite muscle.
If the cramp is in your calf, you want to dorsiflex the ankle. This is done by actively lifting the top of the foot towards your shin, rather than using a piece of furniture to stretch the calf out for you.
If you have cramping in the muscles at the back of your thigh, you want to activate the muscles at the front of your thigh. This is done by actively flexing the foot towards your shin straightening the knee,
There are several suggestions of preventative measures for cramp in the research:
Regular stretching and strength training of a muscle that is prone to cramps, for example doing 20-30 heel raises, 3 x a day and then stretching the calf muscles afterwards.
Replenish salts lost in exercise, if cramps are occurring after activities where you have sweated a lot.
Appropriate management of any underlying medical condition that is contributing to the cramps.
References
Allen, R.E. & Kirby, K.A., (2012) 'Nocturnal Leg Cramps'. Am Fam Physician, 86(4):350-355
Miller, T.M. & Layzer, R.B.,(2005) 'Muscle cramps'. Muscle Nerve 32: 431– 442
Photos: Kindel Media, Boys in Bristol Photography, Yan Krukau