College Pitchers Demonstrate Directional Differences in Shoulder Joint Position Sense Compared With Controls

Context: The relationship between overhead throwing and its effect on proprioception is not well understood. It is important to gain a better understanding of how these are related, to protect overhead athletes from an increased risk of injury. Objective: To investigate proprioceptive alterations in the overhead thrower's shoulder. Design: Cross-sectional study. Independent variables are limb (dominant and nondominant), group (thrower or control), and target angle. Dependent variables are joint position sense and range of motion. Setting: An orthopedic biomechanics lab and university athletic training facility. Participants: Twelve Division I baseball pitchers and 13 nonthrowing control subjects. Intervention: Shoulder proprioception was assessed using an active joint repositioning task administered with an iPod Touch. Main Outcome Measure: Root mean square error and constant error of repositioning angles were used to assess accuracy and directional patterns, respectively. Results: Both groups demonstrated significantly higher joint acuity at the 80 degrees external rotation target angle compared with 60 degrees (1.5 degrees [0.5 degrees] P = .01). There were no differences in accuracy between groups. Constant error revealed differing repositioning patterns between limbs for the pitchers and also between groups for the dominant side. Although the throwing shoulder overshot the target angles by 0.4 degrees, all nonthrowing shoulders undershot by an average of 2.7 degrees. Conclusions: There is no difference in shoulder joint position sense accuracy between throwers and nonthrowers, although both groups display increased accuracy closer to their end range of external rotation. The throwing shoulder demonstrates a different repositioning pattern, overshooting the desired target angle, while all other shoulders undershoot.