Fig. 6. Sarcomere excursion ranges measured in the model frog and in experimental frogs. Arrows represent the starting (arrow tail) and final (arrow head) sarcomere lengths predicted by the model frog at the starting and take-off positions of a jump. Sarcomere lengths were predicted by simulating fixed-end contractions at the start position and then at the take-off position. Bars represent ± 1 S.D. (N=6) from the mean sarcomere lengths measured in experimental frogs when placed (and fixed) at the starting and take-off positions of a jump. Each row shows data for one muscle (model, arrow; experimental frogs, bars). The muscles corresponding to each row are shown to the right. Muscle abbreviations are as follows: semimembranosus (SM), gracilus major (GR), adductor magnus dorsal and ventral heads (Add and ADv), cruralis (CR), gluteus magnus (GL), semitendinosus ventral and dorsal heads (STv and STd), iliofibularis (ILf), iliacus externus (ILe), iliacus internus (ILi), sartorius (SA) and tensor fascia latae (TFL). Also plotted is the sarcomere length/tension relationship for frog SA (dashed line; Gordon et al., 1966). In general, the model accurately predicted the starting and final sarcomere lengths of experimental frogs, and most muscles operated over a range where at least 85 % of maximal tetanic force could be produced.