Summary

Quantitative evaluation for muscle tightness of latissimus dorsi

Abstract

Purpose

Tightness of the latissimus dorsi (LD) and the teres major are contributing factors to a loss of overhead shoulder elevation and cross body abduction, which causes more stress to shoulder and elbow at full layback position each and every throw in throwing athletes. Most of conventional physical tests evaluating the LD tightness are only qualitative methods. The purpose of this study is to introduce LD angle test which we devised to evaluate muscle tightness of the LD quantitatively.

Methods

We evaluated 72 throwing athletes with shoulder or elbow injuries using the LD angle test (the mean of age with 16.1 yrs). The LD angle was measured as follows.: At first, we measured a passive shoulder flexion angle with keeping his shoulder external rotated maximally, and second, after returning his shoulder to neutral rotated position, measured that again. We designed the difference of shoulder flexion angle between two different rotated shoulder positions as the LD angle. We statistically examined the difference of the LD angle between throwing and non-throwing shoulders.

Results

The average of LD angle of the throwing shoulders and that of the non-throwing shoulders is 26.7+-9.4 deg., and 15.0+-9.8 deg., respectively. The LD angle of the throwing shoulders was significantly bigger than that of the non-throwing shoulders (p < 0.05).

Discussion

As the LD inserts into a floor of humeral intertubercular groove, the LD is wound around the humerus during shoulder external rotating. The LD angle test emphasize, and could help to evaluate quantitatively the difference of the LD tightness between throwing and non-throwing shoulder.

Conclusion

We devised a quantitative method to evaluate the LD tightness, called LD angle test.