Biofeedback and musculoskeletal disorders

Work related musculoskeletal disorders (WRMD) are a major source of lost productivity, employee health care costs and disability. LIght duty, computer operation and light manufacturing jobs are typical of those in which muscle loads are low but static postures and repetitive actions lead to problems.

The majority of interventions to date for WRMD have focused on ergonomics which can be successful in 20-30% of cases. However, it is still possible to work incorrectly within an ergonomically correct workstation. Evan minor deviations in workstation arrangements can induce significant muscle overuse.

EMG Biofeedback procedures in which surface EMG is used to provide mulit-modal feedback can be used to readily evaluate how muscles are actually being used by the individual worker in their job role and alos train that worker to use their muscles more effectively. EMG Biofeedback procedures can be used to fine tune ergonomic interventions and train workers how to relax muscles effectively during breaks.

 The trapezius muscles are used for EMG electrode placement

The trapezius muscles are used for EMG electrode placement

The diagram above shows the trapezius muscle which is frequently used for surface EMG recording with active electrodes placed on the posterior occipital, upper trapezius and mid-scapular parts of the muscle.

Typically when examining this muscle group each location is examined bilaterally along with other measures such as respiration rate, skin temperature and even blood-volume pulse. It is quite common to find co-contraction of the upper trapezius in which the shoulders are tense when the arms, toes or even the eyebrows are raised. It is alos common to find patterns of "breath holding" with muscle contraction that are damaging of relaxation.  Some clinicians use the built-in stress test in the NeXus Biotrace software which provides a good overview of the accumulated stress patterns being held in the body.  The trapezius is a good place to focus on as it is involved in many movements of the head, neck and upper extremities. The feedback provided to the client aims to assist finding the correct posture and level of relaxation in the trapezius muscle. The feedback may be as simple as providing a display of the constantly changing level of EMG in the trapezius muscle and instructing the client to reduce the magnitude of this level. Of course with a NEXus biofeedback system you can set thresholds to deliver various forms of audio-visual feedback as deemed suitable by the clinician.

Recommeded reading - "Work Related Musculosketal Disorders" by Susan Middaugh. in Biofeedback - A Practitioners Guide, 4th Edition. Edited by Schwartz and Andrasik. Guilford Press 2016.