Grounded running in quails: Simulations indicate benefits of observed fixed aperture angle between legs before touch-down

Adjustments of global and hindlimb local properties during the terrestrial locomotion of the common quail (Coturnix coturnix)

“…Theoretical models show that grounded running simulated with an aperture angle strategy is less unstable and less sensitive to inaccuracies in angle tuning than the same model simulated with the angle of attack Andrada et al, 2013).…”

“…This approach assumes that the virtual leg behaves like a linear spring. To enable comparison with other species, we present global and local parameters in dimensionless form, following Andrada and co-workers Andrada et al, 2013). Dimensionless global leg stiffness was defined as k=kl 0 /mg.…”

“…Dimensionless global leg stiffness was defined as k=kl 0 /mg. The dimensionless global leg compression (ψ) related to the compression of the spring at mid-stance is equal to the GRF in body weight [ψ=GRF/mg=k(l 0 -l)/mg (see Andrada et al, 2012;Andrada et al, 2013)]. …”

“…For walking and running, we applied the commonly used angle of attack as the TD strategy. For grounded running, the aperture angle between legs was preferred (following Andrada et al, 2012;Andrada et al, 2013).…”

“…Although torques are relatively higher for crouched legs, the demand for high speed and/or acceleration distance per step, i.e. high locomotor performances (Günther et al, 2004), or the need to cope with rough terrain (Daley and Usherwood, 2010;Birn-Jeffery and Daley, 2012;Andrada et al, 2013), may be criteria enforcing such a leg configuration. In humans or other larger animals, swing leg inertia and decrease of effective mechanical advantage [ratio of the extensor muscle moment arm to the moment arm of the GRF (Biewener, 1989)] prevent such postures during locomotion, and grounded running is mostly avoided.…”