Changes in glenohumeral translation, electromyographic activity, and pressure-pain thresholds following sustained or oscillatory mobilizations in stiff and healthy shoulders: Results of a randomized, controlled laboratory trial

Abstract

Study designRandomized Controlled Laboratory Study. BackgroundPosterior glide glenohumeral (GH) mobilizations are utilized to improve motion and decrease pain in patients with shoulder pathologies, thought to be due to capsular stretch and neurophysiologic effects. However, it remains unclear how different GH mobilizations influence mobility, rotator cuff (RC) activity, and pain processing, or if effects are different in stiff (≥15-degree loss of passive motion in any plane) rather than healthy shoulders. ObjectivesTo compare the effects of oscillatory and sustained posterior GH mobilizations on translation, RC activity, and pressure pain threshold (PPT) in stiff and healthy shoulders. MethodsEighty-eight participants, (44 control, 44 stiff shoulders) were randomly assigned to one of two mobilization conditions. Pre-post intervention measurements of PPT, GH translation via ultrasound imaging, and RC activity assessed via electromyography were performed. Sustained or oscillatory grade III posterior GH mobilizations were then provided to all participants. Data were analyzed using tests of difference and regression modeling. ResultsSustained glides (2.8 ± 3.3 mm) demonstrated significantly greater changes in translation compared to oscillatory glides (1.1 ± 3.9 mm), p = .028. Stiff shoulders demonstrated higher total RC activity than controls both pre (+24.51%, p = .004) and post-intervention (+23.10%, p = .01). Small changes in PPT occurred across all conditions, none reaching clinically meaningful levels. ConclusionSustained mobilizations resulted in greater changes in GH translation. RC activity was higher in the stiff shoulder group, and remained higher post-intervention despite gains in GH translation, suggesting a mechanical rather than neurophysiologic effect. There was no meaningful difference in PPT between modes of mobilization. Level of evidenceTherapy, Randomized Controlled Laboratory Study, Level 1b.