Kangaroos are known for their unique locomotion style, hopping at various speeds. Interestingly, their metabolic energy expenditure remains relatively constant, unlike other running animals. This study explores the role of postural adaptations in this phenomenon. The researchers created a 3D kangaroo musculoskeletal model, analyzing the kinematics and kinetics of hopping. They found that increasing ankle dorsiflexion and metatarsophalangeal plantarflexion likely decrease ankle effective mechanical advantage (EMA), leading to increased energy absorption and tendon stress. These posture-mediated changes may enable kangaroos to store and return more elastic energy at faster speeds, contributing to their efficient locomotion. However, this mechanism may also limit the performance of large kangaroos due to the risk of tendon rupture. The study highlights the importance of understanding the relationship between posture and locomotor energetics in kangaroos and other animals.
