Influence of seat lumbar support adjustment on muscle fatigue under whole body vibration: An in vivo experimental study.

ABSTRACT

BACKGROUND: In order to alleviate muscle fatigue and improve ride comfort, many published studies aimed to improve the seat environment or optimize seating posture. However, the effect of lumbar support on the lumbar muscle of seated subjects under whole body vibration is still unclear. OBJECTIVE: This study aimed to investigate the effect of lumbar support magnitude of the seat on lumbar muscle fatigue relief under whole body vibration. METHODS: Twenty healthy volunteers without low back pain participated in the experiment. By measuring surface electromyographic signals of erector spinae muscles under vibration or non-vibration for 30 minutes, the effect of different lumbar support conditions on muscle fatigue was analyzed. The magnitude of lumbar support d is assigned as d1= 0 mm, d2= 20 mm and d3= 40 mm for no support, small support and large support, respectively. RESULTS: The results showed that lumbar muscle activation levels vary under different support conditions. For the small support case (d2= 20 mm), the muscle activation level under vibration and no-vibration was the minimum, 42.3% and 77.7% of that under no support (d1= 0 mm). For all support conditions, the muscle activation level under vibration is higher than that under no-vibration. CONCLUSIONS: The results indicate that the small support yields the minimum muscle contraction (low muscle contraction intensity) under vibration, which is more helpful for relieving lumbar muscle fatigue than no support or large support cases. Therefore, an appropriate lumbar support of seats is necessary for alleviating lumbar muscle fatigue.