A neurologist explains what’s going on when your chest muscle (pecs) keeps twitching.

Does your chest muscle keep twitching?

“For those of you who bench press and are bulking up, the major upper chest muscle that provides the strength for pushing up the weights is the pectoralis major,” says Anthony P. Geraci, MD, Founder and Director of neurOasis Neurology, Clinical Assistant Professor of Neurology, NYU School of Medicine.

“It would be very normal to feel a twitch in the chest, and many people feel that the twitch is deep and perhaps even under the pectoralis major,” continues Dr. Geraci.

“Well, there are only two muscles under the pectoralis major: the pectoralis minor and the intercostal muscles, neither of which contribute much to the power needed to bench press.

“The pectoralis minor rotates our upper arm, and the intercostals allow us to expand our chest when we inspire (breathe in).

“If you feel a twitch in your chest but don’t actually see it, that is because muscle twitches can occur anywhere in the muscle, and if they are in the deep part of the pectoralis major you probably won’t see it depending on the bulk of your muscle.

“Not to worry though, it is still just a benign fasciculation (twitch), and you can keep on pushing up that bar!”

What is the biochemical explanation for a twitch in the chest during or following exercise? When a muscle cell is stimulated by exercise, chemical changes occur, and one of the outcomes of this is “injury” to the cell membrane. This alteration in the muscle fiber’s “chemical soup” leads to random firing of nerves that contract the fiber.