Skip to main content

Research Repository

Advanced Search

Variation in limb loading magnitude and timing in tetrapods

Granatosky, M C; McElroy, E J; Lemelin, P; Reilly, S M; Nyakatura, J A; Andrada, E; Kilbourne, B M; Allen, V R; Butcher, M T; Blob, R W; Ross, C F


M C Granatosky

E J McElroy

P Lemelin

S M Reilly

J A Nyakatura

E Andrada

B M Kilbourne

V R Allen

M T Butcher

R W Blob

C F Ross


Comparative analyses of locomotion in tetrapods reveal two patterns of stride cycle variability. Tachymetabolic tetrapods (birds and mammals) have lower inter-cycle variation in stride duration than bradymetabolic tetrapods (amphibians, lizards, turtles, and crocodilians). This pattern has been linked to the fact that birds and mammals share enlarged cerebella, relatively enlarged and heavily myelinated Ia afferents, and γ-motoneurons to their muscle spindles. Tachymetabolic tetrapod lineages also both possess an encapsulated Golgi tendon morphology, thought to provide more spatially precise information on muscle tension. The functional consequence of this derived Golgi tendon morphology has never been tested. We hypothesized that one advantage of precise information on muscle tension would be lower and more predictable limb bone stresses, achieved in tachymetabolic tetrapods by having less variable substrate reaction forces than bradymetabolic tetrapods. To test this hypothesis, we analyzed hindlimb substrate reaction forces during locomotion of 55 tetrapod species in a phylogenetic comparative framework. Variation in species-means of limb loading magnitude and timing confirm that, for most of the variables analyzed, variance in hindlimb loading and timing is significantly lower in species with encapsulated versus unencapsulated Golgi tendon organs. These findings suggest that maintaining predictable limb loading provides a selective advantage for birds and mammals by allowing for energy-savings during locomotion, lower limb bone safety factors, and quicker recovery from perturbations. The importance of variation in other biomechanical variables in explaining these patterns, such as posture, effective mechanical advantage, and center-of-mass mechanics, remains to be clarified.


Granatosky, M. C., McElroy, E. J., Lemelin, P., Reilly, S. M., Nyakatura, J. A., Andrada, E., …Ross, C. F. (2019). Variation in limb loading magnitude and timing in tetrapods. Journal of Experimental Biology,

Journal Article Type Article
Acceptance Date Nov 22, 2019
Publication Date Nov 27, 2019
Deposit Date Dec 12, 2019
Publicly Available Date Nov 28, 2020
Print ISSN 0022-0949
Publisher The Company of Biologists
Peer Reviewed Peer Reviewed
Public URL


Downloadable Citations