Muscle recruitment patterns of selected upper extremity muscles in Chiropractors within the eThekwini Municipality while performing a simulated sacroiliac joint manipulation

Abstract

Background: Spinal manipulative therapy in the form of a high velocity, low amplitude manipulation, is a specialised therapeutic technique utilised by chiropractors and other manual therapists. Little is known about the shoulder muscular recruitment pattern utilised by practitioners/student’s to deliver this technique. This study aims to profile the muscle recruitment patterns of selected upper extremity musculature during a simulated sacroiliac joint manipulation to provide objective teaching material for future spinal manipulative therapy students regarding this specific manipulation. Methods: A quantitative, descriptive, observational design in which surface electromyography (sEMG) was used captured muscle activation patterns of 11 shoulder muscles in 20 qualified chiropractors who practiced in the eThekwini Municipality. Muscle activity was recorded while the chiropractors performed a simulated sacro-iliac joint manipulation, while simultaneous live video recording was obtained. The manipulation was assessed during its three phases: preload, thrust and resolution. Participants gave informed consent. Raw data was processed and normalised for comparability. Results: All 11 muscles displayed activity throughout the three phases of the adjustment. During preload, the clavicular and sternal pectoralis major and biceps brachii had the greatest mean and median muscle activation magnitude, with the middle and upper trapezius and clavicular pectoralis major showing the greatest maximum muscle activation magnitude. In the thrust phase all muscles showed high activity levels, except for the posterior deltoid which showed moderate activation. The middle and lower trapezius and infraspinatus had the greatest mean, median and maximum muscle activation magnitude. During the resolution phase, the greatest median muscle activation magnitude was found in the middle and lower trapezius and posterior deltoid muscle. This was similar to the greatest mean and maximum muscle activation with the triceps brachii replacing the lower trapezius. The maximum force output during the adjustment was averaged at ± 1.9 Kg. Conclusion: This study highlights the role of the shoulder muscles, specifically the pectoralis and the scapular stabilizer muscles, especially the middle trapezius, in the execution of the spinal manipulative technique investigated in this study. Future studies should confirm these findings in larger population where subgroup analysis can be undertaken.