Shoulder External Rotation Flexibility in Tennis Players

Abstract

Novotny etal., (J Orthop Res. 2000 Mar;1 8(2): 190–4) showed it is possible to develop a device and protocols to quantify shoulder internal/external rotation range of motion (ROM) and resistance to the associated motion. PURPOSE: The purpose of this project was to develop a device to measure shoulder external rotation (ER) flexibility in an orientation relevant to overhand athletics. A secondary purpose was to determine if relationships exist among flexibility measures in advanced tennis players. METHODS: Twenty-seven advanced (NTPR rating >5.0) male tennis players (age = 22.4 ± 7.3 yrs) participated in the study. The device was built to measure both ER range of motion and the associated resistance in an overhand orientation (upper arm abducted at 90° and in the scapular plane). A load cell measured resistance to ER (torque) and a potentiometer was mounted to the device to measure external rotation ROM (degrees). Flexibility measures included the resistance onset angle (ER angle at 1 N-m of resistance), ER ROM (end ROM), and ER stiffness (slope of torque vs. angle best fit line). Pearson product moment correlations were used to determine if significant relationships existed among flexibility measures. RESULTS: All flexibility measures were highly variable. The resistance onset angle ranged from 80–124° (mean = 100 ± 13°), ER ROM ranged from 87–162° (122 ± 17°), and stiffness ranged from 1.6–4.0 °/N-m (2.4 ± 0.7 °/N-m). No relationship was found between the resistance onset angle and ER stiffness (r = 0.14, p = 0.43), however, a significant positive correlation was found between the resistance onset angle and ER ROM (r = 0.83, p <0.01). No relationship was found between ER ROM and ER stiffness (r = 0.11, p = 0.60). CONCLUSIONS: To our knowledge, this is the first study to objectively quantify resistance to shoulder external rotation in overhand athletes. In this study, tennis players with early resistance onset angles tended to cease ER ROM sooner. Interestingly, the resistance onset angle and ER stiffness appear to be independent.