Index of synergy ΔVy as a function of the normalized swing time (mean ± SE, 5 cats) computed for the vertical paw position in space of 5 elemental variables. A: forelimb, regular walking. B: hindlimb, regular walking. C: forelimb, ladder walking. D: hindlimb, ladder walking. The top horizontal dotted line indicates the theoretical maximum of ΔVy (1.25); the bottom dotted line indicates the theoretical minimum of ΔVy (−5.0, see text for details). Solid diamonds indicate 10% time bins of swing for which ΔVy is significantly different from zero (P < 0.05).