The human body comes with some strange quirks. Stacker reveals the explanations behind some of the weirdest reactions, like ...

Add Yahoo as a preferred source to see more of our stories on Google. Many of us have felt a muscle in some part of our body suddenly and involuntarily tighten, causing a twitch or even severe cramp.

Though many people experience muscle twitching, it's often incorrectly identified as a muscle spasm. While both are involuntary contractions of a muscle, muscle spasms and muscle twitching aren't ...

Menstrual cramps, also known as dysmenorrhea, are a common experience for many girls and women during their monthly periods.

There is something strangely unsettling about an eye that refuses to stay still. It starts as a tiny flutter near the eyelid.