Abstract
In ostriches, the toes are the only body parts that contact loose sand surfaces. Thus, toe interphalangeal joint motions may play vital biomechanical roles. However, there is little research on ostrich phalangeal joint movements while walking or running on sand. The results from the three-dimensional motion track analysis system Simi Motion show that gait pattern has no significant effect on the key indicators (angles at touch-down, mid-stance, lift-off and range of motion) of the toe joint angles. The motion of the toe phalanges when walking and running on sand is basically the same. The ground medium is the key factor that changes the toe postures adopted by ostriches during the stance phase in slow to fast locomotion. The 3rd toe and the 4th toe are connected by the interphalangeal ligament, and the motions of the MTP3 and MTP4 joints are highly synchronized on a loose sand substrate. The 3rd toe and 4th toe are coupled to maintain static balance in slow locomotion and dynamic balance in fast locomotion. In addition, the gait pattern has a marked effect on the range of forward displacement of the toenail (YTN). The ostrich toenail plays an important role in preventing slip and provides traction at push-off in a sandy environment. The metatarsophalangeal joint plays an important role in energy saving during fast locomotion on loose sand substrates. Simulation reveals that the particle velocity field, particle force field and sand particle disturbance in the running gait are denser than those in the walking gait.
Highlights
The ostrich (Struthio camelus) is acknowledged as the fastest and largest extant bipedal terrestrial animal with remarkable speed and exceptional endurance during locomotion on sandy environment and wasteland [1,2,3,4]
Because the 3rd toe and the 4th toe are connected by the interphalangeal ligament, the motions of the MTP3 and MTP4 joints were highly synchronized; on loose sand substrate, the 3rd toe and 4th toe were coupled as a whole with the 3rd toe as the primary load bearing element with the 4th toe as the complementary load-sharing element to mainly ensure the lateral stability of the permanently elevated metatarsophalangeal joint
The three-dimensional motion track analysis system Simi Motion shows that gait pattern has no significant effect on the key indicators of the toe joint angles (α, β, γ, θ, φ, ψ) and that ostrich toe phalanges motion postures are basically the same
Summary
The ostrich (Struthio camelus) is acknowledged as the fastest and largest extant bipedal terrestrial animal with remarkable speed and exceptional endurance during locomotion on sandy environment and wasteland [1,2,3,4]. The ostrich can run for 30 minutes at 50 km/h, moving at a speed of 70 km/h for short sprints. It has a remarkable combination of speed and endurance. The supra-jointed toe posture is the unique adaptation of the ostrich. This is because the metatarsophalangeal joint and the proximal phalanx of both toes are permanently elevated above the ground plane [5]
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