Fig 3. Overview of the instrumented castor wheel on the treadmill.

Left: side and front view of the castor wheel with a wedge-shaped connector and force sensor. The round white wedge defining the rake and cant angle is mounted directly to the castor plate. The wedge was rotated with respect to the force sensor to vary the swivel angle. Middle: CAD drawing of the castor wheel set-up. The beam can freely rotate at the H-frame, and weights (black) were used to increase the normal force on the castor wheel. Right: Top view of the castor wheel set-up on the treadmill. The castor wheel is located directly under the black weight.