Mon Nov 03 09:30:00 UTC 2025: News Article:

Kangaroos’ Hopping Secret Revealed: Ankle Posture Key to Energy Efficiency

Sydney, Australia – November 3, 2025 – For years, scientists have been baffled by the remarkable energy efficiency of kangaroos. Unlike most animals, kangaroos don’t significantly increase their energy expenditure as they hop faster. A new study published in eLife may have finally cracked the code, revealing the crucial role of ankle posture in this unique ability.

Researchers from Australia, the UK, and the US found that kangaroos actively modulate the leverage at their ankle joint as they hop. By bending their legs more and adjusting their ankle and toe angles, they can increase the amount of elastic energy returned by their powerful Achilles tendon. This allows them to meet higher mechanical demands without requiring their muscles to perform extra work, effectively decoupling speed from metabolic cost.

The team used 3D motion capture and force plates to record the movements of red and eastern grey kangaroos hopping at varying speeds. They then built a computer model to analyze joint kinematics, rotations, and tendon stress. The results showed that as kangaroos hopped faster, they bent their legs more, increasing the force on the Achilles tendon, which stored and released more energy.

While this remarkable adaptation allows kangaroos to hop efficiently, the study also warns that it pushes their tendons to their limits. This could potentially limit their size and agility. The researchers suggest future studies should examine kangaroos across a broader range of sizes and further investigate tendon stress at high speeds.

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