Title: Relationship between Trunk Strength, Movements, and Throwing Speed In Youth Baseball Players
Abstract: Trunk muscle strength plays an important role in adult baseball players in injury prevention and providing trunk stability for throwing speed. Physical characteristics and neuromuscular control are immature in youth baseball players. More concentration paid on the relationship between trunk strength, movements, and throwing velocity in these players may contribute to their training. PURPOSE: To determine the relationships between trunk strength, trunk movements, and the throwing speed. METHODS: Sixteen youth baseball players (age: 12.0+0.9 yrs) were recruited from two elementary schools. Trunk flexion and extension strength were measured isometrically in sitting position using a dynamometer. Trunk movements of throwing were assessed using a 3D electromagnetic motion analysis system. Ball speed was recorded with a sport radar gun. The relationships between trunk strength, trunk movements, and throwing speed were determined by the correlation coefficients. RESULTS: Ball speed had mild relationships with the strength of trunk flexor (r=0.39) and trunk extensor (r= 0.43). The relationship between extensor/flexor strength ratio (E/F) and the maximal upper torso rotational velocity was r=0.82 and the relationship between E/F and the maximal spinal velocity was r=0.75. The maximal upper and lower torso rotational velocities and spinal rotational velocity were not correlated with ball speed. CONCLUSION: Individual trunk muscle strength may not be the most important factor for throwing in youth baseball players. Strength ratio of E/F may play a role in providing stability for throwing. Throwing mechanics other than maximal torso rotational velocities may affect the throwing performance in youth baseball players.