A single cross-sectional (transverse) slice taken from the centre of the imaging volume was used to construct a finite element model of the calf within the ANSYS 10.0 finite element package (Fig. 1b). Areas of muscle, fat and bone were hand segmented from the MR image using a custom built GUI within Matlab (Mathworks) and meshed using 2d PLANE42 elements. At the edges of the imaging volume some of the calf geometry is not captured in the MR image, the real contour of muscle and fat at these edges was estimated by hand.