(42) RELATIONSHIP BETWEEN ISOMETRIC AND ISOKINETIC ARM STRENGTH IN DIVISION I COLLEGIATE BASEBALL PITCHERS

Purpose: To determine the relationship between isometric and isokinetic arm strength in collegiate baseball pitchers.

Methods: Seventeen Division I pitchers participated in this study during the offseason. Isometric shoulder internal rotation (IR), external rotation (ER), and scaption (S) strength, grip (G) strength as well as total arm (TA) strength (combined IR, ER, S, and G) and arm score (TA strength divided by body mass) for the throwing arm were acquired before and after throwing bullpens and intrasquad games using the ArmCare dynamometer. Additionally, each isometric arm strength score was divided by the pitcher’s body mass and lean body mass to provide relative strength values. Isokinetic strength was tested by using the Biodex System 3 isokinetic dynamometer in the seated position, including: throwing arm shoulder diagonal abduction/adduction and shoulder 90° internal/external rotation at 180, 300, and 450°·sec^-1, forearm pronation/supination at 120, 180, and 240°·sec^-1, and wrist flexion/extension at 120 and 180°·sec^-1. Additionally, individual isokinetic values were combined and divided by the number of speed settings to create an average score. Pearson product-moment correlations were run with an alpha level of 0.05. RESULTS: Significant (p < 0.05) moderate positive relationships existed between average throwing peak torque wrist flexion lean body mass relative strength (ATPTF LMRS) and TA strength (r = 0.518) and G strength (r = 0.508); G strength and throwing peak torque shoulder diagonal abduction 180°·sec^-1 (r = 0.491) and throwing peak torque shoulder diagonal abduction 450°·sec^-1 (r = 0.509). Significant (p < 0.05) moderate negative relationships existed between throwing peak torque forearm supination 180°·sec^-1 and shoulder external rotation throwing arm lean body mass relative strength (ERTARM LMRS) (r = -0.492); throwing peak torque forearm supination 240°·sec^-1 (TPTS240) and shoulder external rotation throwing arm relative strength (ERTARM RS) (r = -0.496) and ERTARM LMRS (r = -0.540); throwing peak torque forearm pronation 240°·sec^-1 (TPTP240) and shoulder internal rotation throwing arm lean body mass relative strength (IRTARM LMRS) (r = -0.522); average throwing peak torque forearm supination and ERTARM LMRS (r = -0.515); average throwing peak torque forearm supination relative strength (ATPTS RS) and arm score lean body mass (LM) (r = -0.576), TA strength (r = -0.528), shoulder external rotation throwing arm (ERTARM) strength (r = -0.563), and ERTARM LMRS (r = -0.591); average throwing peak torque forearm supination lean body mass relative strength (ATPTS LMRS) and arm score LM (r = -0.510), ERTARM strength (r = -0.495), and ERTARM LMRS (r = -0.589).

Conclusions: Meaningful significant relationships existed between isokinetic ATPTF LMRS and isometric G strength and TA strength. PRACTICAL APPLICATIONS: Isokinetic wrist flexion strength relates to isometric G strength and TA strength. Other testing variables do not significantly relate to one another. Though both devices produce valuable information to identify strength deficiencies, imbalances, and inhibited recovery, they provide little data that relates to one another. It is important to understand that the isometric device provides values at specific joint angles without movement while the isokinetic device provides values throughout an entire range of motion at specific speeds.

Acknowledgements: We would like to thank the Louisiana Tech baseball pitchers for participating in this study.