Phase 4 Effects of a Stretching Protocol for the Pectoralis Minor Muscle on This Resting Length and on the 3D Kinematics of the Scapula During Arm Flexion in Asymptomatic Subjects and Patients With Impingement Syndrome

Fifty subjects (25 symptomatic and 25 asymptomatic for shoulder pain) will be recruited. All of them will be initially assessed twice with one week between the assessments. On each day, they will complete two questionnaires (DASH and SPADI) to assess pain and shoulder function. The resting length of the pectoralis minor muscle and scapular kinematics data during arm flexion will also be measured using an electromagnetic tracking system. Initially, the resting length of the pectoralis minor will be measured, and then 3 repetitions of arm elevation in the sagittal plane will be completed. The stretching protocol will be performed daily for 6 weeks. The stretching will be performed with the subject standing, with 90° of arm abduction and 90° of elbow flexion and palm on a flat planar surface. The subject then will place the leg opposite to the flat surface in front of the other with slight knee flexion and tilt the trunk forward like a rigid block and rotate it slightly increasing the horizontal abduction at the shoulder. This procedure will be done 4 times for 1 min and 30s interval between repetitions. After the 6 weeks, the subject will have the same variables from the initial assessments reassessed. For the questionnaires and length of pectoralis minor a two-way ANOVA for repeated measures will be used to check the main effects of group and evaluation and whether there is interaction between them. For scapular internal/external rotation, upward/downward rotation, and tilt anterior/posterior a three-way ANOVA for repeated measures will use to analyze the main effects of group (symptomatic and asymptomatic), elevation angle of the arm (30°, 60°, 90° and 120°) and evaluation (1, 2 and 3) and whether there is evaluation x group x angle interaction. A p value less than 0.05 will be considered significant.