Fig. 3.

The concept of functional morphospace to examine muscle architectural functional specialisations. By relating the fibre length to the physiological cross‐sectional area (PCSA) of a muscle, it can be classified as either force specialised (short fibres, high PCSA), displacement specialised (long fibres, low PCSA), or power specialised (moderate to long fibres, moderate to high PCSA). Bates & Schachner (2012) found that the hip muscles of the alligator Alligator mississippiensis occupy a wider area of functional morphospace, and thus contain a wider range of architectural specialisations, than those in the ostrich Struthio camelus, (A). This pattern is reversed at the knee joint however, with the ostrich muscles displaying more adaptations for power and displacement specialisation than the alligator muscles (B). At the ankle, muscles are more force specialised in the ostrich compared to the more displacement specialised muscles of the alligator (C). Overall, these differences hint at possible adaptations of muscle architecture throughout evolutionary lineages. ADD, adductor femoris; CFL, caudofemoralis longus; FCL, flexor cruris lateralis; ILFB, iliofibularis; IT, iliotibialis.