Kinematics and mechanics of ground take-off in the starling Sturnis vulgaris and the quail Coturnix coturnix.

The mechanics of avian take-off are central to hypotheses about flight evolution, but have not been quantified in terms of whole-body movements for any species. In this study, I use a combination of high-speed video analysis and force plate recording to measure the kinematics and mechanics of ground take-off in the European starling Sturnis vulgaris and the European migratory quail Coturnix coturnix. Counter to hypotheses based on the habits and morphology of each species, S. vulgaris and C. coturnix both produce 80-90 % of the velocity of take-off with the hindlimbs. S. vulgaris performs a countermovement jump (peak vertical force four times body weight) followed by wing movement, while C. coturnix performs a squat jump (peak vertical force 7.8 times body weight) with simultaneous wing movement. The wings, while necessary for continuing the movement initiated by the hindlimbs and thereafter supporting the body weight, are not the primary take-off accelerator. Comparison with one other avian species in which take-off kinematics have been recorded (Columba livia) suggests that this could be a common pattern for living birds. Given these data and the fact that running take-offs such as those suggested for an evolving proto-flier are limited to large or highly specialized living taxa, a jumping model of take-off is proposed as a more logical starting point for the evolution of avian powered flight.

Variable gearing during locomotion in the human musculoskeletal system.

Human feet and toes provide a mechanism for changing the gear ratio of the ankle extensor muscles during a running step. A variable gear ratio could enhance muscle performance during constant-speed running by applying a more effective prestretch during landing, while maintaining the muscles near the high-efficiency or high-power portion of the force-velocity curve during takeoff. Furthermore, during acceleration, variable gearing may allow muscle contractile properties to remain optimized despite rapid changes in running speed. Forceplate and kinematic analyses of running steps show low gear ratios at touchdown that increase throughout the contact phase.