Normalization of the subscapularis belly-press test

Abstract

The purpose of this report is to document the normal range of the subscapularis belly-press test and to define factors that influence it to aid in the assessment of subscapularis function in relevant shoulder pathology and procedures. Both shoulders in 204 patients with no history of shoulder problems were tested with an Isobex machine. Patients were educated on proper technique before testing. Height, weight, age, hand dominance, and gender were all recorded. All measured values were recorded in kilograms. Women had a mean belly-press strength (mean of both arms) of 5.1 +/- 1.9 kg, which was significantly less than the men's strength of 8.4 +/- 2.5 kg (P < .001). The mean difference in belly-press strength between the dominant arm (6.7 kg) and nondominant arm (6.5 kg) was small (95% confidence interval, 0.05-0.4 kg). Multiple regression analysis revealed that mean belly-press strength was significantly related to gender (P = .001), height (P = .006), and weight (P < .001) but not age (P = .320). The belly-press test evaluation for subscapularis strength can be normalized across an average population by gender, height, and weight. Hand dominance and age do not factor in significantly. This test can be useful in evaluating the preoperative and postoperative status of the subscapularis in relevant shoulder injuries and procedures.