Anthropometry

To build a simulated human that moves like a real one, every body part needs a realistic size, mass, centre of mass and inertia. Anthropometry is the science of these measurements.

Sizes: ANSUR II

The 2012 U.S. Army Anthropometric Survey (ANSUR II, Gordon et al. 2014) measured over 6,000 soldiers, with nearly a hundred measurements each: lengths, girths, breadths and heights. Its averages give a realistic set of proportions for an adult body.

Masses and inertias: de Leva

You can’t easily weigh a living person’s thigh. Zatsiorsky and Seluyanov estimated segment masses and inertias by scanning living subjects with gamma rays. De Leva (1996) adjusted their results so that each segment is measured between standard joint centres, which made them easy to use in models. The tables give each segment’s mass as a fraction of total body mass, the position of its centre of mass along its length, and its radii of gyration.

For example, the thigh is about 14 % of a man’s body mass, with its centre of mass about 41 % of the way down from the hip.

A segment’s moment of inertia follows from its mass $m$, its length $L$ and the tabled radius of gyration $k$, a fraction of the length:

$$I = m\,(k L)^2$$

In this project

The fighter is an average adult man: 1.75 m and 77 kg, a welterweight. Segment masses come from de Leva (1996) and limb girths from the ANSUR II survey means. Joint ranges come from the AAOS tables (see range of motion).