Using Thermography to Evaluate the Effects of Arm Flexion and Loading on the Anterior Deltoid during a Simulated Overhead Task
Shoulder injuries are a focus of work related musculoskeletal disorder (WMSD) research due to rising healthcare costs, an aging workforce, and long recovery times. Substantial research has been performed in the area of shoulder WMSDs and a number of risk factors have been implicated in their development; including static loads, repetition, and deviated posture. However, knowledge of underlying pathophysiological mechanisms is limited. Thermography provides a non-invasive technique that may offer clues to unknown physiological markers associated with injury development during job task performance. The objective of this study was to quantify anterior deltoid surface temperature changes as function of changing task demands. Skin surface temperature changes of the anterior deltoid, modified Borg CR-10 ratings, and endurance time during overhead static exertions until exhaustion for two work loads (15 and 30% MVC) and shoulder angles (90o and 115o) were quantified. Ten participants (5 males and 5 females) participated in the study and were free of confounding conditions (such as chronic or acute shoulder injury) and were required to meet body fat percentile requirements. Thermography showed that the higher shoulder angle had a reduced blood flow while there were no differences in temperature for exertion. Modified Borg ratings were not found to be well correlated with temperature values. The findings suggest that workers performing overhead work should minimize their deviated posture when available to prevent a high risk of developing a shoulder WMSD.