Infraspinatus strength assessment before and after scapular muscles rehabilitation in professional volleyball players with scapular dyskinesis

Hypothesis: This study tested the hypothesis that infraspinatus strength in professional volleyball players can be assessed with the scapula free (infraspinatus strength test, IST) and with the scapula retracted (infraspinatus scapula retraction test, ISRT) before and after scapular musculature training.

Materials and methods: A prospective study was performed in 31 professional volleyball players. Isometric strength (kg) of the infraspinatus with IST and with ISRT was recorded by a handheld dynamometer and compared with the values found after 3 and 6 months of rehabilitation. Magnetic resonance imaging was performed to exclude articular and cuff pathology. Pain scores were assessed using a visual analog scale.

Results: The mean increase in the force values of IST was statistically significant after 3 months (P < .01) and 6 months (P < .001) of rehabilitation. The mean difference between IST and ISRT decreased from 4.72 ± 0.007 before rehabilitation to 1.2 ± 0.26 at 3 months and to 0.4 ± 0.006 at 6 months. The mean score for pain was 2.4 ± 1.8 at 3 months and 2.6 ± 1.4 at 6 months.

Discussion: Acquired scapular dyskinesis in overhead athletes can lead to the rotator cuff weakness. Inhibition due to pain and the negative biomechanic effect of scapular dyskinesis results in specific infraspinatus dysfunction that arise with the ISRT.

Conclusions: ISRT is practical and consistent to assess the infraspinatus strength in overhead athletes with scapular dyskinesis. A functional rehabilitation protocol, designed to restore scapular muscles balance and shoulder mobility, is essential in the training program to prevent shoulder dysfunction and improve sports performance.