Differences in Strength and Fatigue Resistance of Scapular Protractors and Retractors Between Symptomatic and Asymptomatic Dyskinesis

Abstract

Context: Scapular dyskinesis is a shoulder dysfunction that can be asymptomatic or associated with pain or weakness. Reduced strength and fatigue resistance of the scapular protractor and retractor muscles that stabilize the scapula might contribute to dyskinesis. Objectives: To determine the strength and fatigue resistance profiles of participants with symptomatic or asymptomatic scapular dyskinesis and compare them with healthy control (HC) individuals using isokinetic assessment. Design: Cross-sectional study. Setting: University hospital. Patients or Other Participants: Twenty HC individuals and 21 overhead athletes with symptomatic (n = 10) or asymptomatic (n = 11) scapular dyskinesis. Main Outcome Measure(s): Strength (peak torque, maximum work), fatigue resistance (total work), and protraction:retraction ratios measured during a closed chain isokinetic protocol (40 repetitions in concentric mode at 24.4 cm/s). Results: The scapular protractors' strength and fatigue resistance were higher (P , .01) in HC individuals (peak torque = 5.0 6 0.9 N/kg, maximum work = 2.4 6 0.5 J/kg, total work = 72.4 6 0.6 J/kg) than in asymptomatic (peak torque = 3.4 6 0.7 N/kg, maximum work = 1.7 6 0.4 J/kg, total work = 50.0 6 13.7 J/kg) or symptomatic (peak torque = 3.8 6 0.6 N/kg, maximum work = 1.8 6 0.3 J/kg, total work = 58.1 6 12.9 J/kg) dyskinetic participants. The symptomatic dyskinetic group presented the highest retractor strength and fatigue resistance (P