2017 Volume 53 Issue 5 Pages 157-166
The purpose of this study was to investigate the effectiveness of lower back support on spinal alignment, electromyograms （EMGs）, and subjective fatigue values. The height of the lower back support, in an experimental automobile seat, was adjusted below L3 and the depth was set at three different settings: 0 mm, －15 mm, and －30 mm. The sacral tilt and the lumbosacral, lumbar lordosis, and thoracic kyphosis angles were measured in twenty healthy males using a spinal measuring device called a “Spinal Mouse”. An EMG of the lumbar muscle, near L5/S1, and the subjective physical fatigue value were measured in eighteen healthy males that sat for twenty minutes under the same conditions. The results showed significant differences in the sacral tilt （p＜0.05）, lumbar lordosis angle （p＜0.01）and the relative value of mean power frequency （MPF）in EMGs （p＜0.05）, resulting from the different seating conditions. The backward sacral tilt increased, the lumbar lordosis angle decreased, and the MPF decreased when the volume of lower back support decreased. Lower back support was considered effective for preventing backward sacral tilt, lumbar curvature flattening, and lumbar muscle fatigue.
