The purpose of this study was to have verified a muscle that began to contract fastest in the punch of boxing. The Fifteen university-age males with no history of chronic low back pain participated in the study. Participants were ranked as BOX (n=8) or CON (n=7). Subjects performed a straight punch with the rear arm (dominant arm). Electromyographic activity of deltoid muscle, rectus femoris muscle, rectus abdominis muscle, external oblique muscle, internal oblique muscle-transversus abdominis muscle; IO-TrA, multifidus muscle were measured. As a result, the IO-TrA was invariably the first contractive muscle in BOX and CON, supporting the hypothesized role of this muscle in spinal stiffness generation
