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

Abstract

For primates and other mammals moving on relatively thin branches, the ability to effectively adopt both above-and below-branch locomotion is seen as critical for successful arboreal locomotion, and has been considered an important step prior to the evolution of specialized suspensory locomotion within our Order. Yet, little information exists on the ways in which limb mechanics change when animals shift from above-to below-branch quadrupedal locomotion. This study tested the hypothesis that vertical force magnitude and distribution do not vary between locomotor modes, but that the propulsive and braking roles of the forelimb change when animals shift from above-to below-branch quadrupedal locomotion. We collected kinetic data on two lemur species (Varecia variegata and Lemur catta) walking above and below an instrumented arboreal runway. Values for peak vertical, braking and propulsive forces as well as horizontal impulses were collected for each limb. When walking below branch, both species demonstrated a significant shift in limb kinetics compared with above-branch movement. The forelimb became both the primary weight-bearing limb and propulsive organ, while the hindlimb reduced its weight-bearing role and became the primary braking limb. This shift in force distribution represents a shift toward mechanics associated with bimanual suspensory locomotion, a locomotor mode unusual to primates and central to human evolution. The ability to make this change is not accompanied by significant anatomical changes, and thus likely represents an underlying mechanical flexibility present in most primates.

A suspensory way of life: Integrating locomotion, postures, limb movements, and forces in two‐toed sloths Choloepus didactylus (Megalonychidae, Folivora, Pilosa)

“…Data were collected while animals walked below an instrumented runway measuring 366 cm in length and 3.10 cm in diameter. During all trials, animals were video‐recorded from a lateral view at 120 fields/s using a GoPro camera (Hero 3 + Black Edition; GoPro, San Mateo, CA) modified with a Back‐Bone Ribcage (Ribcage v. 1.0; Back‐Bone, Ottawa, ON, Canada), which allows the GoPro cameras to be outfitted with interchangeable lenses and eliminates image distortion inherent to the camera (Granatosky, Tripp, & Schmitt, ). Only walking strides (i.e., duty factor over 50%) in which the animal was traveling in a straight path and not accelerating or decelerating (i.e., steady‐state locomotion) were selected for analysis.…”

Patterns of quadrupedal locomotion in a vertical clinging and leaping primate (Propithecus coquereli) with implications for understanding the functional demands of primate quadrupedal locomotion

“…All animals were adults and were clear of any pathologies or gait abnormalities (Table 1). The methods used here have been described extensively elsewhere (Schmitt, 1994(Schmitt, , 1999(Schmitt, , 2003aSchmitt and Lemelin, 2002;Hanna et al, 2006;Granatosky et al, 2016), and will only be summarized below.…”

“…The instrumented portion of the runway consisted of two Kistler force plates (model 9317B) that have been used in previous studies (Bishop et al, 2008;Granatosky et al, 2016). A small section of dowel was secured on one end of each force plate measuring the same diameter as the rest of the runway and large enough to accommodate an entire hand or foot (10 cm).…”

“…Forces for each day of trials were normalized to the weight recorded for that day. The animals were videotaped during trials within a clear plastic enclosure from a lateral view using a GoPro camera (Hero 31 Black Edition; GoPro, San Mateo, CA) modified with a Back-Bone Ribcage (Ribcage v1.0; Back-Bone, Ottawa, ON), which allows the GoPro cameras to be outfitted with interchangeable lenses and eliminates image distortion inherent to the camera (Granatosky et al, 2016). Our previous test of parallax effects using these specific cameras showed that we can record undistorted data over three meters of viewing space with the camera three meters from the line of travel (Granatosky et al, 2016).…”

“…Only walking steps (i.e., duty factor over 50%) in which the animal was traveling in a straight path and not accelerating or decelerating (i.e., steady-state locomotion) were selected for analysis. Steady-state locomotion was determined by calculating the instantaneous speed between subsequent video frames throughout the entire stride, and then using regression analysis to determine whether velocity changed throughout the stride (Bishop et al, 2008;Granatosky, 2015;Granatosky et al 2016). Only strides in which no change in speed (i.e., slope not significantly different than zero) was detected were used for subsequent analyses.…”