Adjusting muscle function to demand: joint work during acceleration in wild turkeys

Area of Science:

• Biomechanics
• Animal Locomotion

Background:

• Understanding the source of mechanical power is crucial for explaining animal acceleration.
• Previous research indicated high mechanical power output in turkey hind limb musculature during running.

Purpose of the Study:

• To determine the source of mechanical power for acceleration in running turkeys.
• To test the hypothesis that net mechanical work per step increases with acceleration at major hind limb joints.

Main Methods:

• High-speed video and force-plate measurements were used to analyze joint moments, velocities, and power output during turkey accelerations.
• Data were collected across a range of accelerations at consistent running speeds.

Main Results:

• Net work per step increased significantly at the hip and ankle joints as a function of acceleration.
• Work output at the knee and tarsometatarsal-phalangeal joint remained independent of acceleration.
• Increased joint work was primarily due to greater angular excursion (muscle shortening), not increased joint moment (muscle force).

Conclusions:

• Hip and ankle extensors are key contributors to the mechanical work required for turkey acceleration.
• Elastic mechanisms likely enhance muscle work at the ankle during acceleration.
• Turkeys primarily increase acceleration by maximizing muscle shortening at the hip and ankle, rather than by increasing muscle force.