Laterality of muscle thickness in athletes who perform throwing and hitting motions

The present study investigates the laterality of muscle thickness (MT) in athletes who perform throwing and hitting motions. Sixty right-handed college athletes (baseball pitchers group, PG; tennis players group, TG; baseball batters group, BG and controls group, CG; all n = 15) participated in this study. Muscle thickness was measured by B-mode ultrasound at the forearm, anterior and posterior upper arm, subscapula, chest, abdomen, lateral abdomen, anterior and posterior thigh and anterior and posterior lower leg. Muscle thickness in the dominant forearm, subscapula, and chest in PG, forearm, chest, anterior and posterior upper arm in TG and the subscapula and chest in BG were significantly larger than those in the non-dominant side. On the other hand, the MT in the non-dominant lateral abdomen in PG, the abdomen and lateral abdomen in TG, and the posterior upper arm and lateral abdomen in BG were significantly larger than those in the dominant side. The ratio of dominant to non-dominant MT was significantly smaller for the internal oblique muscle and total thickness of lateral abdomen in PG, TG and BG than CG. Laterality of the internal oblique muscle and total thickness of lateral abdomen in the non-dominant side is a common characteristic of athletes who perform throwing and hitting motions.