Human tolerance to impact acceleration.

Tolerance to brief impact is related to the imposed velocity change, whilst in longer impacts it is the level of acceleration which is critical. This behaviour results from the dynamic characteristics of the body which, for practical purposes, can be represented as a simple mass spring system. For any given acceleration vector, and for any given system of body restraint, whole body (primary) tolerance can be defined by two parameters--a critical velocity change and a critical plateau acceleration level. Appropriate figures are given for 14 different posture and restraint conditions. It is stressed that these are best estimates (or in some cases, best guesses) and that secondary or tertiary mechanisms of injury, in particular head strikes, must not be ignored in any real-life conditions of impact.