Developing reliable measures of the passive torque-angle relationship for shoulder internal and external rotation: Implications for overhead athletics.

Objectives: 1) Thoroughly assess shoulder flexibility by establishing the passive torque-angle relationship for internal and external rotation with the arm in an overhead athletics position (abducted 90°) and 2) test the reliability of four passive torque-angle measures.

Design: Reliability study.

Setting: Data were collected in a university biomechanics laboratory.

Participants: Bilateral shoulder flexibility of 15 male college students (20.7 ± 1.1 y) was evaluated twice in two sessions over 7-10 days.

Main Outcome Measures: For both ER and IR, reliability was assessed bilaterally (intra-session, inter-session, and inter-tester) for the traditional range of motion measure and three novel kinetic measures: torque at end ROM, resistance onset angle, rotational stiffness. This resulted in 48 total assessments.

Results: Thirty-four assessments had good to excellent reliability (ICC ≥ 0.8), 10 had fair reliability (0.7 ≤ ICC < 0.8), and 4 had poor reliability (ICC< 0.7). Three of the four flexibility measures had a good overall ICC score: ROM (0.83), torque at end ROM (0.84), and resistance onset angle (0.81). The fourth, stiffness, had a fair overall reliability score (0.74).

Conclusions: The passive torque-angle measures should be assimilated into clinical and research settings to determine the relevance to injury, rehabilitation, and performance.