Figure 3

Testing protocol. First 2500 test-cycles were performed in flexion between 15 and 100 N. Cycles 2500 to 7500 were performed in extension between 15 and 150 N. To provoke fatigue failure, the load was then monotonically increased at 0.1 N/cycle. Stiffness was evaluated from quasi-static ramps at 0, 2500 and 7500 cycles as indicated by yellow bars.