Kath Beattie, of Dunedin, asks :-

In a recent column re What causes cramp? the explanation concentrated on that occuring during physical activity and hinted at other causes. From time to time I suffer cramping when I am in bed. I have to roll myself out of bed and stand on the cold floor, then make my way to the kitchen to take 'dolomite' tablets which usually do the trick. I can't recall ever having cramp during or after exercise. Usually the cramp seems to come for no reason that I can think of. What causes these cases?

Phil Sheard, a physiologist at the University of Otago's School of Medical Sciences, responded.

I tried to deal with the less common causes by saying that cramp "..may have several causes, the most common of which..." because with such a short article it obviously isn't possible to describe the full range.

In many cases the precise cause of the cramp is unknown, these are referred to as idiopathic cramps. The factors that are likely to increase the likelihood of anyone suffering from idiopathic cramps are gender (females more likely), pregnancy, age (worse with advancing age), fatiguing exercise (ie a hard days work, or a lot of shopping/gardening/walking having been done), a job or task that requires a lot of standing on a flat or cold surface, muscle injury, use of high heel shoes, dehydration, poor nutrient absorption, a diet low in nutrients required for normal muscle function, or leg posture during sleep.

Some scientists think that the high incidence of lower leg cramps in western society relates to the height of our toilets! Squat toilets common in Asian countries provides regular stretching the leg muscles, but our relatively high toilets deprive us of that opportunity. I doubt that you would view the installation of a squat toilet as a viable solution, but there is a common thread through the literature that suggests that regular stretching of the affected muscles is helpful.

If someone gets cramp in bed (which is quite common) and which is relieved by dolomite suggest that leg posture and nutrient supply are most likely. Muscles are most likely to cramp when they are used in a shortened position. Think about swimming freestyle with the toes pointed to kick in the water, in this position the calf muscles are shortened, as they are in women wearing high heel shoes. Many people sleep with their knees bent and toes pointed, this shortens the calf muscles and increases the likelihood of cramps in the lower leg. Sleeping with toes curled under would increase likelihood of cramps in the muscles of the foot. Calf and toe stretches before bed might help.

The fact that taking dolomite relieves the cramp is important information. Dolomite is a nutritional supplement that is high in calcium and magnesium. Both calcium and magnesium are essential for normal muscle function. Since dolomite improves the condition it may indicate a dietary deficiency in one or both of these minerals which may arise from poor intake or poor absorption. Poor intake is most easily remedied by dairy products which are good sources of calcium, and green veges (especially beans) which are good sources of magnesium. For someone who is lactose intolerant, a lot of the foods that are high in magnesium are also good sources of calcium, such as nuts, seeds, and leafy greens.