I've got a certain amount of back muscle in my chest.

My lumbar spine and back muscle symmetry show much larger discrepancies, a result of too much time at my desk.

Exceptions include when she had knee surgery in 2003 and after straining a back muscle in 2006.

The injury turned out to be a badly pulled back muscle, which required extensive rehabilitation.

Back muscle spasms often cause arching, called opisthotonos.