Is Strength the Main Risk Factor of Overuse Shoulder Injuries? A Cohort Study of 296 Amateur Overhead Athletes

Shoulder pain is one of the most common musculoskeletal complaints in overhead athletes. This study investigated the prevalence of the main risk factors and sex differences related to the development of shoulder pain in a cohort of amateur overhead athletes.

The external rotation/internal rotation (ER/IR) isometric strength ratio <0.75% is the most prevalent risk factor associated to overuse shoulder injuries in both sexes.

Cohort study.

Level 3.

A total of 296 (147 male and 149 female) amateur overhead athletes from handball, volleyball, and water polo participated in this cross-sectional study. Isometric strength, rotational range of motion, and scapular control were analyzed bilaterally. The measurements and motions were randomized between sides.

The ER/IR isometric strength ratio deficit among the disciplines was presented in 264 and 229 out of 296 athletes in the dominant and nondominant sides, respectively. Normalized isometric strength showed significant differences for dominant (P < 0.01; ε² = 0.47) and nondominant IR (P < 0.01; ε² = 0.60). No significant differences were observed between dominant (P = 0.44; ε² = 0.05) and nondominant ER (P = -0.24; ε² = 0.07). The prevalence of glenohumeral IR deficit (GIRD) (P = 0.81) and total arc of motion differences (TAMD) (P = 0.39) was low, with no difference between sexes. Male (16.3%) and female (12.1%) athletes had low rate of obvious scapular dyskinesis in their dominant shoulders.

Muscle strength was the most prevalent risk factor. The ER/IR ratio imbalance was present in both sides, without sex differences. Risk factors such as scapular dyskinesis, GIRD, and TAMD were present in low percentages, without sex differences.

It is advisable to implement shoulder exercises to strengthen ER muscles to decrease differences between internal and external rotators and prevent injuries in overhead athletes.