An improved method of stature measurement for quantitative determination of spinal loading. Application to sitting postures and whole body vibration.

A refined procedure for measuring stature is described; this provides a reproducibility error of 0.4 mm. The procedure accommodates the natural diurnal change in stature and permits estimation of the net stature change caused by a change in spinal loading. A series of measurements done with a cohort of 20 young and middle-aged persons showed that stature decrease was related linearly to the quasi-static load on the spine. The coefficient of proportionality between load and height loss was inversely proportional to the cross-sectional area of the lumbar discs. This method was used to investigate sitting postures and whole-body vibration to demonstrate the applicability of the procedure to quantify spinal strain (and, therefore, estimate comparative loading) in applied ergonomics. Sitting invariably led to an increase in stature, regardless of the type of chair used or the posture maintained. Whole-body vibration did not induce any loss of stature. Thus, this novel approach was able to enhance understanding of spinal behavior under different loading conditions.