[binarypaean]

Your body has to move calcium ions in and out of (striated) muscles to trigger contractions. This is done through "calcium channels". Mg2+ is an antagonist to the activation of calcium channels.

You need enough calcium to achieve a strong reliable contraction, and enough magnesium to keep the channels "closed" when they should be closed (among very many other physiological uses).

In short, you need a balance of calcium and magnesium for reliable muscle function. A gross excess or lack of either is bad.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5652077/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4315934/

[saiojd]

Thank you, this is interesting. It's kind of weird, realizing I don't understand my own body at all.