Electromyographic Evaluation of a New Approach to Descending Stairs While Carrying a Stretcher

Abstract

One of the frequently encountered strenuous tasks performed by firefighter/paramedics (FFPs) is carrying a victim down the stairs on a stretcher. This study was designed to biomechanically evaluate new equipment that allows the stretcher to essentially be rolled down the stairs. The device called the Decent Control System looks like a pair of “tank treads” with a friction brake that span multiple steps was developed for this purpose (figure 1). We recruited 11 two-person teams of professional firefighters to test this approach. Electromyographic (EMG) data were obtained from each person as they carried and rolled the stretcher down a flight of stairs. Of the 8 muscles sampled from each firefighter, 4 muscles, including the left and right Erector Spinae showed significant reductions with the new approach. On average the 90th percentile normalized activity level for the Leader's (the FFP descending the stairs backwards) Erector Spinae decreased by 27% while the follower decreased 37%. The mean activity levels across the sampling period for these same muscle groups mounted on the stretcher shown also decreased by a similar amount. In summary the Decent Control System reduced the activity in two of the primary low back muscles used when lifting. Such reductions, if experienced in the field, lessen the biomechanical loads transmitted to the spine and the potential for muscle over-exertion injuries.