Does the unusual phenomenon of sustained force circumvent the speed-endurance trade off in the jaw muscle of the southern alligator lizard (Elgaria multicarinata)?

The jaw muscles of the southern alligator lizard, Elgaria multicarinata, are used in prolonged mate-holding behavior, and also to catch fast prey. In both males and females, these muscles exhibit an unusual type of high endurance known as sustained force in which contractile force does not return to baseline between subsequent contractions. This phenomenon is assumed to facilitate the prolonged mate-holding observed in this species. Skeletal muscle is often subject to a speed-endurance trade off. Here we determine the isometric twitch, tetanic, and isotonic force-velocity properties of the jaw muscles at ~24°C as metrics of contractile speed and compare these properties to a more typical thigh locomotory muscle, to determine whether endurance by sustained force allows for circumvention of the speed-endurance trade-off. The specialized jaw muscle is generally slower than the more typical thigh muscle; time to peak twitch force, twitch 90% relaxation time (p<0.01), and tetanic 90% and ..., , , # A comparison of the force-velocity properties of the jaw muscle of the southern alligator lizard (*Elgaria multicarinata*) used in long-lasting mating behaviors to a more typical thigh muscle.

[https://doi.org/10.5061/dryad.mgqnk996q](https://doi.org/10.5061/dryad.mgqnk996q)

The data file Nguyenetal_DryadData_2024.xlsx consists of Excel sheets (BodySize&MuscleDimensions, IsometricProperties, RepresentativeTwitchFigure1A, RepresentativeTetanicFigure1B, BoxpotFigure1C) of data points of figures in the manuscript for the isometric properties (e.g., twitch and tetanic contraction times, stress values, and physiological cross-sectional area, CSA) and the corresponding boxplots (TPT: time to peak tension; TP90: time to 90% of peak tension; RT50: time to 50% relaxation, measured from peak to 50% relaxation; RT90: time to 90% relaxation, measured from peak to 90% relaxation), force velocities individual data points and curve fits, and power curves individual data points and curve fits....