Muscle Pain Induces a Shift of the Spatial Distribution of Upper Trapezius Muscle Activity During a Repetitive Task: A Mechanism for Perpetuation of Pain With Repetitive Activity?

Objective: An association exists between repetitive movements and the development or perpetuation of neck-shoulder muscle pain. The mechanisms underlying this association remain unclear. This observational study investigated the effect of upper trapezius muscle pain on the distribution of upper trapezius activity during repetitive lifting. It was hypothesized that nociception would change the distribution of activity resulting in activation of muscle regions which would not normally be active during the task.
Materials and Methods: Healthy men repeatedly lifted a box with a cycle time of 3 seconds for 50 cycles, at baseline, following injection of isotonic and hypertonic saline into the upper trapezius muscle and 15 minutes after the last injection. High-density surface electromyography (EMG) was recorded from the upper trapezius using a grid of 64 electrodes. The EMG amplitude was computed for each location to form a map of the EMG amplitude distribution.
Results: During the painful condition, the overall EMG amplitude was lower compared with all other conditions (P

Source: The Clinical Journal of Pain - October 7, 2017 Category: Anesthesiology Tags: Original Articles Source Type: research