Figure 4.

Passive Flexions of a Locust Hind Leg Are Driven by Passive Forces Originating within the Femur-Tibia Joint Itself, Whereas Passive Extensions Are Driven by Passive Forces Arising in the Extensor Tibiae Muscle

(A) The time course of passive flexion movements of an intact leg (black symbols), the same leg after flexor tibiae muscle and tendon ablation (blue symbols), and after complete ablation of both flexor and extensor tibiae muscles and their tendons (red symbols). Two trials are shown for each condition. The tibia was released at 0.05 s (arrow). Ablating both muscles had no effect on the velocity of flexion but resulted in a slightly larger total amplitude of movement. The inset shows resting femorotibial joint angles of six intact isolated locust hind legs (black symbols) and the same legs following ablation of both the extensor and flexor tibiae muscles and tendons (red symbols). IF, intact flexed; IE, intact extended; AF, ablated flexed; AE, ablated extended.

(B) When both the extensor and flexor tibiae muscles and their tendons were ablated, there was virtually no passive tibial extension following release from full flexion. Data are from the same animal as that shown in (A) and are shown at the same scale (see also Figures 3A and S4).

See also Figure S4.