Compliant walking in primates: Elbow and knee yield in primates compared to other mammals

Abstract

It has been suggested that primates utilize a compliant gait to help reduce peak locomotor stresses on their limbs (Schmitt [1994] J. Hum. Evol. 26:441-458; Schmitt [ 1998] Primate Locomotion, p. 175-200; Schmitt [ 1999] J. Zool. Lond. 248:149-160). However, the components of such a gait, i.e., increased step length, prolonged contact time, and substantial limb yield, have only been documented on a handful of primate species. In order to explore the generality of this claim, elbow and knee angles during walking were documented at touchdown, midstance, and liftoff in a sample of primates, carnivores, marsupials, rodents, and artiodactyls, all under 25 kg. Limb yield was calculated as the change in angle from touchdown to midstance, and re-extension as the change in angle from midstance to liftoff for both forelimbs and hind limbs. Use of a compliant gait (as reflected in significant limb yield) in primates was confirmed for both forelimbs and hind limbs. However, there was variability within primates in the degree of either elbow or knee yield. Surprisingly, marsupials were found to exhibit almost as much elbow yield and even greater knee yield than primates. Carnivores and rodents display a modest amount of limb yield during walking, while artiodactyls appear to display a relatively stiff gait. These data are consistent with the suggestion that the use of a compliant gait to attenuate peak substrate reaction forces may have facilitated the primate invasion of a small-branch niche. However, limb compliance (as reflected by elbow or knee yield) does not appear to be exclusive to the primate order.

Gait kinetics of above- and below-branch quadrupedal locomotion in lemurid primates

“…The first model, proposed by Reynolds (1985aReynolds ( ,b, 1987 and supported by Larson and Stern (2009), suggests that primates actively shift weight caudally on their relatively protracted hindlimbs using powerful muscular retractors of the hindlimb. The second model, proposed by Schmitt (1998Schmitt ( , 1999 and tested by Larney and Larson (2004), argues that primates change vertical stiffness of their limbs by increasing limb yield, contact time and angular excursion. These models are not mutually exclusive and both provide important mechanisms by which locomotor forces on the limbs can be moderated (Schmitt and Hanna, 2004;Young, 2012).…”

Arboreal locomotion in rats – the challenge of maintaining stability

“…By contrast, lower protraction angles during terrestrial locomotion are related to higher positions of the proximal pivots of the limbs (Fig.9). In primates, the greater degree of forelimb excursion during arboreal locomotion is proposed as a way of preventing limb interference (Larney and Larson, 2004;Schmidt, 2008;Wallace and Demes, 2008). Unfortunately, the effects of small branches on fore-and hindlimb protraction in primates are unknown because protraction angles have only been investigated in the upper arm (Schmitt, 2003c).…”

Forelimb proportions and kinematics: how are small primates different from other small mammals?

“…Is the 'new' forelimb posture at touchdown really better adapted to the specific demands of primate locomotion than the 'old' one? One argument against this assumption is that the extended and protracted forelimb of primates is more susceptible to gravitational loading than the crouched posture of other mammals as the substrate reaction force vector is far removed from the limb joints (Biewener, 1983;Schmitt, 1999;Larney and Larson, 2004;Schmidt, 2005b). Only the ability of many primates to reduce the weight borne by the forelimb may help to overcome this problem (Reynolds, 1985).…”