What does traction relieve muscle spasms?

Disc: It may stretch muscle and relieve tension of the discs.

Used for nerve: Muscle spasms, in some cases, are prompted by nerve irritation or compression, but can be associated with underlying arthritis or stiffness causing secondary muscular effects. If involving neck or lower back, the traction can separate structures to alleviate bone-bone contact and even widen the area to decrease nerve contact. The muscle pain is thus relieved by such an approach.