Horse (Equus caballus)

The foreleg shows a 1st Order lever: The scapula and humerus bones create the fulcrum; the anterior deep pectoral muscle is contracting, pulling the scapula anteriorly; the foreleg is moving forward.

The hindleg shows a 3rd Order lever: the ilium and femur bones create the fulcrum; the semitendinosus and biceps femoris muscles are contracting, pulling the tibia and fibula posteriorly; the hindleg is moving back.


This shows the body after the in-force muscles have acted to move the limbs. The different positions of the in-lever and out-lever arms show how the muscles have produced movement of the bones.

The first-order lever has a velocity ratio around 11/1; the third-order lever has a velocity ratio around 13/1.

These high velocity ratios show that horse limbs (and most other ungulates) are built for speed more than for power.