Overview
Key words: Low back pain, trunk kinematics, whole body vibration
Timeline: 2012 - 2013
Researchers: Joel Cort (Principal Investigator, University of Windsor), Jim Dickey (University of Western Ontario). Student researcher: Danielle MacIntyre (University of Windsor)
Funder: Centre of Research Expertise for the Prevention of Musculoskeletal Disorders (CRE-MSD)
Project type: Seed Grant
Sector/Workplace type: Transportation; automotive industries
Themes:
Theme
1
Injury
mechanisms
Theme
3
Risk
assessment
and
hazard
identification
Background/rationale
Whole body vibrations (WBV), especially in large-hauling-commercial-vehicles, has been linked as a risk factor to low back pain/injury. Although exposure limits have been developed, the mechanics of vehicle-induced musculoskeletal injuries are not fully understood.
Research question/objectives/methods
The purpose of the project was to further develop an understanding of how vehicle-induced musculoskeletal injuries occur by measuring surface electromyography (sEMG) of trunk muscles and capturing kinematics of the trunk, head and arms during sudden movement protocols. Six male participants were divided into a control group (CG) and a vibration group (VG) meant either 10 minutes of quiet sitting or random vibration, respectively. Afterwards, participants stood on a robotic platform and were subjected to 40 trials of known and unknown directional perturbations.
Key findings
A mean power frequency (MnPF) analysis showed an increase in thoracic erector spinae muscle activity in the VG compared to the CG. This was postulated to be a result of the vibrating seat causing greater motion of the upper torso than the lumbar spine. WBV decreased muscle contraction intensity. Almost all muscles showed, with biological significance, higher activation in the CG versus the VG with the exception of one muscle which showed similar activation levels (< 1% MVC difference). Vibration thus affects the body’s ability to resist sudden and unintended motions. Having prior knowledge of perturbation direction aids in muscle activation in response to the perturbation. For muscle sEMG onsets that could be determined, an average delayed onset of 32 milliseconds was found in the VG compared to the CG.
Implications for the prevention of MSDs
From this pilot study, WBV seems to negatively impact the neuromuscular response following intertial based trunk perturbations. WBV seems to cause a delayed and decreased muscle response to sudden movements. Poor neuromuscular coordination is a risk factor for mechanical failure following kinematic disturbances.