The effect of backrest inclination on spinal height changes was tested during static sitting and seated whole-body vibrations. The vibration input was sinusoidal with a frequency of 5 Hz and an acceleration of 0.1 g rms. The backrest inclinations tested were 110° and 120°. The 110° backrest caused less shrinkage than did the 120° during static sitting, whereas the opposite was true when vibration was present, although the differences between the backrests were not statistically significant. Only when the results were compared with results from exposure to unsupported sitting were differences statistically significant for both static sitting and seated vibrations when the 110° backrest was used and for vibration with the 120° backrest. The authors conclude that an inclined backrest reduces the effects of vibration. More importantly emphasis should be places upon seats and seat materials that can attenuate vibration.
Abstract