But if they're not used right, they can strain muscles and even cause back pain.

Montgomery strained a muscle running before the first full practice.

"We can participate in sports with no concern about straining a muscle."

"With the light gravity it's hard to imagine anyone straining a muscle."

He strained a muscle in his left side Friday and was placed on the disabled list yesterday.

You can strain a muscle with an unexpected pull or twist.

He strained a muscle on his left side in the first inning, and pitching through the pain did not help.

He thought he had strained a muscle, but it didn't go away.

He also strained a muscle in his lower leg.

Running out a ground ball to end the second inning, he strained a muscle in his upper thigh.