@mo53
Just googled and came up with this, hope it might be of some help
Dehydration: Sports and other vigorous activities can cause excessive fluid loss from
perspiration. This kind of
dehydration increases the likelihood of true cramps. These cramps are more likely to occur in warm weather and can be an early sign of
heat stroke. Chronic volume depletion of body fluids from diuretics (medicine that promote urination) and poor fluid intake may act similarly to predispose to cramps, especially in older people. Sodium depletion has also been associated with cramps. Loss of sodium, the most abundant chemical constituent of body fluids outside the cell, is usually a function of
dehydration.
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Low potassium:
Low potassium blood levels occasionally cause muscle cramps, although it is more common for low potassium to be associated with muscle
weakness.