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Characterizing trunk muscle activations during simulated low-speed rear impact collisions
Kayla M Fewster1, Daniel Viggiani1, Chad E Gooyers1,2
1a Faculty of Applied Health Science, Department of Kinesiology , University of Waterloo , Waterloo , Ontario , Canada.
Traffic Injury Prevention
|April 24, 2019
Summary
During low-speed rear-end collisions, lumbar spine muscle activation is minimal. This suggests muscle activity contributes little to joint loads, supporting simplified models for injury analysis.
Area of Science:
- Biomechanics
- Spinal Cord Injury Research
Background:
- Understanding occupant biomechanics during rear-end collisions is crucial for injury prevention.
- Low-speed impacts are common, yet their effect on lumbar spine musculature requires further elucidation.
Purpose of the Study:
- To evaluate lumbar spine muscle activation patterns during unanticipated and braced simulated low-speed rear-end collisions.
- To determine the contribution of muscle activation to internal joint loads.
Main Methods:
- Eleven volunteers underwent 22 low-speed (4 km/h) sled tests simulating rear-end impacts.
- Surface electromyography (EMG) measured trunk muscle activation; accelerometers recorded lumbar spine motion.
- Peak accelerations, muscle activation delay, onset time, and EMG magnitudes (normalized to MVC) were analyzed.
Main Results:
- Bracing slightly reduced peak lumbar acceleration (~15%), but differences were not statistically significant.
- Only thoracic erector spinae showed peak activation >10% MVC during unanticipated impacts.
- Peak muscle activation occurred later in unanticipated (296 ms) versus braced (241 ms) impacts.
Conclusions:
- Lumbar spine muscle activation is low in magnitude during unanticipated low-speed rear-end collisions.
- Muscle activation likely contributes minimally to internal joint loads in the lumbar spine.
- Findings support simplified joint models and cadaver/ATD testing for analyzing rear-impact biomechanics.
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