Twitches and spasms are most common in the thighs, calves, hands, arms, belly, ribcage, and the arches of your foot. They can involve part of a muscle, all of it, or a group of muscles. Doctors aren’t always sure why they happen, but a few common triggers can set them off. Triggers for twitching eyes range from stress and smoking to wind, bright light, too much caffeine, and lack of sleep. Your muscles depend on minerals, like potassium and magnesium, to work properly. If you’re running low on them, your body sends you a message with cramps and spasms. Exercise or heavy sweating can deplete you, but some medications can, too. If you don’t get enough to drink, your muscles will be more likely to twitch and spasm. - WebMD