Relationship between hand-behind-back motion and internal rotation with the shoulder in extension.

[Purpose] The purpose of the present study was to investigate whether the extent of shoulder internal rotation measured in the extended position of the shoulder could be a good indicator of hand-behind-back motion ability. [Participants and Methods] We measured internal rotation with the shoulder in extension in 26 healthy adults (average age, 25.2 ± 2.5 years). Internal rotation was measured passively in the supine position at 30° of shoulder extension. Additionally, a hand-behind-back motion was performed, and the hand-behind-back distance was measured. The relationship between the angle of internal rotation with the shoulder in extension and hand-behind-back distance was evaluated using Pearson's product-moment correlation. The level of significance was set at 5%. [Results] The angle of internal rotation with the shoulder in extension and the hand-behind-back distance correlate significantly. [Conclusion] Internal rotation with the shoulder in extension is a good indicator of hand-behind-back motion.