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Motor Control of Compliant Landings
Does muscle activity change due to surface compliance or stiffness? I discovered that cane toads do not change their muscle activity prior to landing or after touchdown when their arms are working to slow the toad down. This finding suggests toads adopt the same strategy to stick the landing no matter the surface stiffness. If you watched the short video to the left and still want to learn more check out my other research videos including my dissertation defense. |
Above are examples of the same toad hopping on to a rigid surface (left) and a compliant or springy surface (right; 5 millimeters of displacement per body weight).
The top plots are the limb extension ratio (LER; in purple) throughout the jump, where a LER of 1 would be the arms fully stretched out and a value of 0 having the hands flexed up against the chest.
Here the blueish-gray box represents the time when the arms are airborne during jump and potentially getting ready to land. The white period of each graph before this is when the toad is just starting to jump and the arms are still touching the ground, and the white period after the blueish-gray box is when the arms have touched back down and they are working to slow the toad down.
The second through fifth rows of plots show the muscle activities of the Deltoidius, Pectoralis, Anconeus, and Palmaris longus muscles, from 2nd from the top to the bottom plots.
The top plots are the limb extension ratio (LER; in purple) throughout the jump, where a LER of 1 would be the arms fully stretched out and a value of 0 having the hands flexed up against the chest.
Here the blueish-gray box represents the time when the arms are airborne during jump and potentially getting ready to land. The white period of each graph before this is when the toad is just starting to jump and the arms are still touching the ground, and the white period after the blueish-gray box is when the arms have touched back down and they are working to slow the toad down.
The second through fifth rows of plots show the muscle activities of the Deltoidius, Pectoralis, Anconeus, and Palmaris longus muscles, from 2nd from the top to the bottom plots.
Next Step
Finding out that cane toads do not alter their muscle activity regardless of landing compliance suggests the changes in joint work I found in my first project are likely not due to the toads actively tuning their muscle activity in preparation for or while landing on a springy surface.
However, one of the major limitations of my work thus far has been keeping the takeoff platform rigid. The toads are always jumping off a rigid surface and may anticipate landing on a similar surface. Just like how you or I may not expect to have a soft landing when jumping off a concrete slab. Learn more about my third project which attempts to answer whether cane toads use sensory info during their takeoff to predict landing conditions.
Finding out that cane toads do not alter their muscle activity regardless of landing compliance suggests the changes in joint work I found in my first project are likely not due to the toads actively tuning their muscle activity in preparation for or while landing on a springy surface.
However, one of the major limitations of my work thus far has been keeping the takeoff platform rigid. The toads are always jumping off a rigid surface and may anticipate landing on a similar surface. Just like how you or I may not expect to have a soft landing when jumping off a concrete slab. Learn more about my third project which attempts to answer whether cane toads use sensory info during their takeoff to predict landing conditions.