Fig. 1. (A) Anatomy of the triceps surae muscle group and the Achilles tendon (adapted from Gray's Anatomy). (B) Photograph of the attachment of the ultrasound probe to the leg. Three markers are rigidly attached to the probe by way of a fibreglass mould. This setup allowed for images of the gastrocnemius muscle–tendon junction to be visualised in the sagittal plane of the leg (see Fig. 2).