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Biol Lett. Aug 23, 2010; 6(4): 486–489.
Published online Feb 3, 2010. doi:  10.1098/rsbl.2009.1005
PMCID: PMC2936198
Do toads have a jump on how far they hop? Pre-landing activity timing and intensity in forelimb muscles of hopping Bufo marinus
Gary B. Gillis,1* Trupti Akella,2 and Rashmi Gunaratne1
1Department of Biological Sciences, Mount Holyoke College, South Hadley, MA 01075, USA
2Department of Bioengineering, School of Engineering and Applied Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
*Author for correspondence (ggillis/at/mtholyoke.edu).
Received December 2, 2009; Accepted January 8, 2010.
Abstract
During jumping or falling in humans and various other mammals, limb muscles are activated before landing, and the intensity and timing of this pre-landing activity are scaled to the expected impact. In this study, we test whether similarly tuned anticipatory muscle activity is present in hopping cane toads. Toads use their forelimbs for landing, and we analysed pre-landing electromyographic (EMG) timing and intensity in relation to hop distance for the m. coracoradialis and m. anconeus, which act antagonistically at the elbow, and are presumably important in stabilizing the forelimb during landing. In most cases, a significant, positive relationship between hop distance and pre-landing EMG intensity was found. Moreover, pre-landing activation timing of m. anconeus was tightly linked to when the forelimbs touched down at landing. Thus, like mammals, toads appear to gauge the timing and magnitude of their impending impact and activate elbow muscles accordingly. To our knowledge these data represent the first demonstration of tuned pre-landing muscle recruitment in anurans and raise questions about how important the visual, vestibular and/or proprioceptive systems are in mediating this response.
Keywords: forelimbs, toads, muscle, EMG, locomotion, jumping
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