SICB 2016: Lizard Sprint Speed is Limited by Muscle Twitch Speed

SICB is off to a very anole-y start in Portland! There have been anole-focused talks and posters all day, and your intrepid team of AA reporters are on the scene.

At Monday’s poster session, Noel Parks (an undergraduate at Brown University working with Chris Anderson and Thomas Roberts) presented her research on muscle contraction and sprint kinematics in Anolis sagrei and A. cristatellus. The team performed laboratory sprint trials with the two species at a range of inclines, and then using muscle tissues from the same lizards used in the trials, they measured how fast the M. ambiens pars ventralis (a hindlimb muscle critical for locomotion) can contract and relax after stimulation, a measure they call muscle twitch time.

Noel Parks and her poster at SICB 2016.

For both species, Noel and her colleagues found that stance time (the amount of time a foot is in contact with the ground) and swing time (the amount of time the limb is moving forward) are limited by the muscle twitch time. Thus, muscle twitch time may constrain the sprint speed of these animals. Further, at steeper inclines, stance and swing times more closely approached muscle twitch time. The two species differed in these speeds, however, as A. sagrei had faster twitch, stance, and swing times than A. cristatellus.

This work gives us another interesting piece of the puzzle in the larger story of anole locomotor performance!