Fig. 7

The triangle inequality may be used to explain that the average difference in upper arm elevation between the two analyses was lower than the difference between the two reference postures. The upper triangle illustrates the case that is likely to occur most of the work time. In that case the difference ∆ = b – c < a, where a is the difference between the two reference posture points, and b – c is the difference between the two analyses. In the (unusual) middle case ∆ = b – c = 0; the elevation point is equally far from the two reference posture points, and in the (unusual) lower case, ∆ = b – c = a, the elevation point is in line with and outside the two reference posture points, and the difference between the two reference analyses will be the same as the difference between the two reference postures. So ∆ is always less or equal to the difference between the two reference posture points