Magnesium tablets

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A club mate has suggested taking magnesium tablets to ward-off cramp in the latter stages of a race (in addition to drinking adequately). Does anyone have any experience of these? Did they help? What is the science behind this?

Cheers!

Having good supplies of Calcium, Magnesium, and Zinc are needed for muscle contraction, they're all easy minerals to get so drink some milk or something. I don't know the science behind them except for calcium, had to learn it for my biology class..

yes, i get really annoying cramps after 1.5hours of exercise. it doesnt matter if im cycling for that long, or running off the bike, it just happens. rode with a guy who used to cycle competitively, and he told me the same thing-- Mg tablets. he said something about Mg making water re-enter the muscles more rapidly. with regards to the muscle and surrounding interstitial fluid, a membrane wraps around the muscle, and water is present within this 'bag', and outside it. water gets depleted within the muscle as you exercise, and usually it takes 3days for water levels to be completely restored. Mg speeds up the rehydration from outside the muscle to inside-- maybe altering the membrane permeability.

im studying physiology at uni, but they never taught me this!!!