This document addresses human exposure to multiple mechanical shocks, and it formulates requirements for the measurement of multiple shocks. The results of these measurements are then analyzed to provide information for the assessment of the risk of adverse health effects to the vertebral end-plates of the lumbar spine for seated individuals due to compression. Other injuries could develop even when there is no injury to the end plate.
NOTE 1 Multiple mechanical shocks are shocks of different magnitude and shape that occur frequently at regular and irregular intervals during the measurement period.
NOTE 2 As proposed in the annexes, the assessment of the current injury risk is based on measured representative exposures in combination with the individual exposure history. Prospective risks can be assessed by anticipated exposure durations. Manufacturers of measurement equipment are encouraged to develop a possibility for an on-site evaluation of the exposure.
Two exposure regimes are distinguished in this document: one for severe conditions and one for less severe conditions.
NOTE 3 Clause 4 contains the delineation of the two regimes.
This document is applicable for unweighted vertical accelerations that have peak values up to 137,3 m/s2 (14 g) measured at the seat-occupant interface beneath the ischial tuberosities over a 0,01 Hz to 80 Hz measurement bandwidth.
NOTE 4 The measurement bandwith is defined in 5.1.
Caution is necessary when applying the method to severe exposures, particularly since peak accelerations of 137,3 m/s2 (14 g) are close to the physical limit that a spine can tolerate.