Leg cramps at night

Q: My seven-year-old son gets lower leg cramps quite often when he is asleep. This usually happens after he has had Physical Education lessons in school or after an hour or so at the playground. Sometimes, they recur a couple of days later.

His siblings, who are two and three years younger than him and just as active, do not have this problem. Does my son lack any vitamins or minerals in his diet that cause these cramps?

A: Leg cramps are not uncommon in active and growing children. Cramps are involuntary and sudden contraction of muscles, usually in the lower limbs, and can be painful when the contraction is prolonged. These cramps are part of 'growing pains' in children and they typically occur at night or when the child is resting.

Muscle fatigue, or overuse, is the most common cause. Your child might be over-exerting himself during physical activities in school or at the playground.

Lactic acid build-up in the muscles from poor fluid intake and overuse of the leg muscles can lead to painful contractions, even a few hours after the exercise.

Other contributing factors include dehydration and electrolyte imbalances, most notably calcium and magnesium.

Electrolytes like sodium, potassium, calcium and magnesium in our body are involved in many cellular functions, one of which is muscle contraction and relaxation. An imbalance in these electrolytes can predispose a child to leg cramps.

Deficiency in vitamins B1 (thiamine), B5 (pantothenic acid) and B6 (pyridoxine) may also, directly or indirectly, cause cramps.

To treat the cramps, you could massage the affected muscle groups, put a warm compress on the area and stretch the muscles.

To prevent cramps, your son should do warm-up and cool-down stretching before and after exercises.

Adequate fluid intake and electrolyte replacement, when there is excessive perspiration, are also essential in preventing cramps. Taking milk products for calcium and green leafy vegetables for magnesium may prevent recurrent cramps in children lacking these minerals.

In rare cases, serious conditions like leukaemia or renal impairment may cause recurrent and painful cramps, which may need a doctor's review.

Dr Chan Poh Chong

Dr Chan Poh Chong is the head and senior consultant at the division of ambulatory and adolescent paediatrics at the University Children's Medical Institute, National University Hospital.

This article was first published in Mind Your Body, The Straits Times.