Fig. 6. Transmission electron micrographs (longitudinal section) through the tongue retractor muscle (m. hyoglossus) in a relaxed (left) and a maximally extended (right) state. Note the perforations in the Z-disks (arrowhead) characteristic of supercontracting muscle. Also note the relatively short I-bands and the large overlap between the thick and thin filaments. The force produced by a muscle is proportional to the number of cross bridges engaged and, thus, to the overlap between the thick and thin filaments.