Translations of the Humeral Head Elicit Reflexes in Rotator Cuff Muscles That Are Larger Than Those in the Primary Shoulder Movers

Frontiers in Integrative Neuroscience

Neuroscience

Daniel Ludvig¹  Eric J. Perreault²  Margaret S. Coats-Thomas³  Constantine P. Nicolozakes³  Amee L. Seitz⁴ 

[1] Department of Biomedical Engineering, Northwestern University, Evanston, IL, United States;Shirley Ryan AbilityLab, Chicago, IL, United States;Department of Biomedical Engineering, Northwestern University, Evanston, IL, United States;Shirley Ryan AbilityLab, Chicago, IL, United States;Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL, United States;Department of Biomedical Engineering, Northwestern University, Evanston, IL, United States;Shirley Ryan AbilityLab, Chicago, IL, United States;Feinberg School of Medicine, Northwestern University, Chicago, IL, United States;Department of Physical Therapy & Human Movement Sciences, Northwestern University, Chicago, IL, United States;

关键词: stretch reflex;    glenohumeral joint;    glenohumeral stability;    reflex amplitude;    reflex latency;    reflex gain-scaling;    fine-wire intramuscular electromyography;    surface electromyography;   

DOI  :  10.3389/fnint.2021.796472

 received in 2021-10-16, accepted in 2021-12-22,  发布年份 2022

来源: Frontiers

【 摘 要 】

Muscle activation helps stabilize the glenohumeral joint and prevent dislocations, which are more common at the shoulder than at any other human joint. Feedforward control of shoulder muscles is important for protecting the glenohumeral joint from harm caused by anticipated external perturbations. However, dislocations are frequently caused by unexpected perturbations for which feedback control is essential. Stretch-evoked reflexes elicited by translations of the glenohumeral joint may therefore be an important mechanism for maintaining joint integrity, yet little is known about them. Specifically, reflexes elicited by glenohumeral translations have only been studied under passive conditions, and there have been no investigations of how responses are coordinated across the functional groupings of muscles found at the shoulder. Our objective was to characterize stretch-evoked reflexes elicited by translations of the glenohumeral joint while shoulder muscles are active. We aimed to determine how these responses differ between the rotator cuff muscles, which are essential for maintaining glenohumeral stability, and the primary shoulder movers, which are essential for the large mobility of this joint. We evoked reflexes using anterior and posterior translations of the humeral head while participants produced voluntary isometric torque in six directions spanning the three rotational degrees-of-freedom about the shoulder. Electromyograms were used to measure the stretch-evoked reflexes elicited in nine shoulder muscles. We found that reflex amplitudes were larger in the rotator cuff muscles than in the primary shoulder movers, in part due to increased background activation during torque generation but more so due to an increased scaling of reflex responses with background activation. The reflexes we observed likely arose from the diversity of proprioceptors within the muscles and in the passive structures surrounding the shoulder. The large reflexes observed in the rotator cuff muscles suggest that feedback control of the rotator cuff augments the feedforward control that serves to compress the humeral head into the glenoid. This coordination may serve to stabilize the shoulder rapidly when preparing for and responding to unexpected disturbances.

【 授权许可】

Unknown   
Copyright © 2022 Nicolozakes, Coats-Thomas, Ludvig, Seitz and Perreault.