Background & Aims
Shoulder pain is one of the most frequent chronic musculoskeletal dysfunctions, mostly prevalent in psychologically stressed populations and women. Furthermore, it is associated with alterations in muscle strength and movement avoidance behavior. Patients have difficulties in performing everyday life activities with fear of increasing pain, which leads to avoidance of moving the limb and it may cause more muscle activity dysfunction. This association is not commonly made in literature, especially with the shoulder joint and with specific measurement instruments. Therefore, the aim of this study is to evaluate and compare possible associations between peak torque during shoulder external rotation (ER) and internal rotation (IR) and avoidance behavior in patients with subacromial pain syndrome (SPS) and, moreover, compare possible disparities between gender.
Methods
Patients included were between 18 to 55 years old, no historic of traumatic injuries and surgeries. Exclusion criteria were total rotator cuff tear, fracture and overhead athletes. Movement avoidance behavior was assessed using the Avoidance Daily Activities Photo (ADAP) Shoulder Scale prior to the muscle test. Strength evaluation was by an isokinetic dynamometer (Biodex 4) in a sitting position with 45° of abduction in the scapular plane, 30° of IR and 30° of ER at 60°/s speed. At the beginning of the evaluation, the participants performed three submaximal repetitions of each movement to familiarize themselves with the equipment. Strength assessment by three concentric isokinetic contractions was stimulated with verbal feedback and the day’s pain intensity was collected with the analogue numeric scale. The multiple linear regression model was used. The dependent variable was the ADAP Shoulder Scale and peak torque of ER and IR were the independent variables.
Results
Seventy-one participants were evaluated (forty-five women and twenty-six men; age 46?8,9 years; body mass index 29.6.3?6.2 kg/m2) with a pain intensity of 5?2.4. The analysis resulted in a significant model [F(2,68) = 11,3; p < 0,001; adjusted R²= 0.227]. IR peak torque (?=0.110; t=3,79; p=<0.001; 95%CI -0,864 to 0,002) is associated with movement avoidance, while ER peak torque (?=-0.014; t=-1,18; p=0.242) is poorly associated with movement avoidance. Moreover, only the analysis of men peak torque with avoidance behavior presented a significant model [F(2,22) = 5,60; p = 0,011; adjusted R²= 0.277].
Conclusions
Peak torque of IR of the shoulder movement is capable of being associated with whether people with SDS exhibit movement avoidance behavior or not. This study shows that a lesser peak torque of internal rotators of the shoulder in the male population is associated with movement avoidance.
References
1. Peña G., Núñez J., et al. Relationship between pain intensity, physical factors, pronociceptive pain modulation profile and psychological vulnerability on upper limp disability in older patients with chronic shoulder pain. Int. J. Environ. Res. Public Health 2022;
2. Ansanello W, Dos Reis FJDSJ, Tozzo MC, et al. Development of the Avoidance Daily Activities Photo Scale for Patients with Shoulder Pain. Phys Ther 2022; 102: 1–11.