Abstract
Objectives:
When pitching a baseball, players must use the intrinsic muscles of the hand to effectively control and propel the ball. Grip and pinch strength are metrics that reflect the strength of these muscles and can be easily obtained both in clinic and in the training field. Grip strength has been found to be a marker of an individual’s overall muscular strength1 and a strong predictor of pitched ball kinetic energy in young baseball players.2 Additionally, there has been a reported weak, but not significant, association between elbow injury and grip strength in youth players.3 Diminished grip and pinch strength could lead to a decrease in dynamic stability of the medial elbow resulting in increased load on the UCL. Further, research is limited comparing grip and pinch strength to the load at the elbow during throwing. Therefore, the purpose of this study was to evaluate bilateral grip and pinch strength and its relationship to both ball velocity and elbow varus torque in high school pitchers.
Methods:
Data from 25 high school pitchers were included in this study (182.8±5.4 cm, 78.7±10 kg). Pitchers were tested for bilateral grip strength using a digital dynamometer and a pinch gauge to measure three-point pinch strength. Pitchers were then evaluated while pitching full-effort fastballs at 480 Hz using a 3D motion capture system (Motion Analysis Corp., Santa Rosa, CA). Each pitcher’s maximum grip strength, pinch strength, and fastest pitch were used in the analysis. T-tests were used to compare measures bilaterally and linear regression was used to evaluate the relationship between grip and pinch strength to ball velocity and elbow varus torque.
Results:
Average ball velocity was 35.3±0.3 m/s (79.0±0.7 mph) and elbow varus torque was 70.9±3.3 Nm. Grip strength (477.9±57.5 vs 474.9±57.2 N, p<0.001), and pinch strength (101.0±16.5 vs 95.2±16.0 N, p<0.001) were greater in the throwing arm compared to non-throwing arm. Throwing arm grip strength was significantly related to both ball velocity (r2=0.020, p=0.020) and elbow varus torque (r2=0.167, p=0.034), but both correlations were considered weak. There were no significant associations between pinch strength to either ball velocity (r2=0.067, p=0.124) or elbow varus torque (r2=-0.023, p=0.486). When normalizing pinch and grip strength to player mass (N/kg), there was a statistically significant, but weak, relationship between pinch strength and elbow varus torque (r2=0.139, p=0.049). There were no significant associations between normalized grip and elbow varus torque (p=0.112) or normalized grip/pinch and ball velocity (p=0.509 and p=0.523, respectively).
Conclusions:
Grip strength revealed to be positively correlated, albeit weakly, with both ball velocity and elbow varus torque. Pinch strength normalized to mass was weakly correlated to elbow varus torque. These findings suggest that while grip strength may play a role in pitching performance and injury risk, its impact is limited. Other factors, such as height, weight, and pitch specialization, should also be considered. Adolescent growth may impact the relationship between a pitcher’s strength and his injury risk. Future research should investigate grip and pinch strength acutely (between innings and throwing days) and chronically (over the course of a season) to fully assess its benefits or detriments to the throwing arm.