Figure 2

Strain signals measured on the cortex of a proximal epiphyseal chicken femur at the opposite side to the impact (as shown in the right bottom frame of plot (a)) using the experimental apparatus described in Fig. 1. This setup delivers bending-related tensile strains to the bone cortex (and coupled strain gauge) at the instant of impact. Hence, a in strain-time plot (a) for a control (unaltered) bone specimen which was subjected to impact energy of 0.3 joule, and did not break, a first peak shows tensile strains which are then counteracted by some elastic recoil response from the bone (second peak). This bone specimen was not included in further data analyses, and its data are shown here to illustrate the loading state in the bone during trials, and in particular, the decay of dynamic strains post-impact and the elastic recoil response of the bone. The strain-time plot (b) shows data for a specimen from which 0.12 g of trabecular bone were removed (~17% of the trabecular mass). The point of specimen failure and the part of the strain-time curve used to determine the strain rate are depicted. Scale of strains: 1 Volt = 500 μm/m.