My muscles twitch and shake when I am tired. What could be the reason for this?

Hi there, this can be due to mineral levels falling below the necessary levels when drained by activity. Magnesium and potassium are the most obvious deficiencies here. As potassium can be tricky to supplement, I would suggest trying a magnesium supplement first. It can also be useful to have an overhaul by a cranial osteopath, as there may be some structural adjustments that could be rectified, making you less prone to these twitches.