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.

Rory McIlroy withdrew from the Arnold Palmer Invitational due to back spasms, but is expected to compete in The Players ...

Rory McIlroy withdrew from the third round of the Arnold Palmer Invitational on Saturday when he felt muscle spasms in his back that were not going away.