Three-dimensional kinematics of the pelvis and hind limbs in chimpanzee (Pan troglodytes) and human bipedal walking

Abstract

The common chimpanzee (Pan troglodytes) is a facultative biped and our closest living relative. As such, the musculoskeletal anatomies of their pelvis and hind limbs have long provided a comparative context for studies of human and fossil hominin locomotion. Yet, how the chimpanzee pelvis and hind limb actually move during bipedal walking is still not well defined. Here, we describe the three-dimensional (3-D) kinematics of the pelvis, hip, knee and ankle during bipedal walking and compare those values to humans walking at the same dimensionless and dimensional velocities. The stride-to-stride and intraspecific variations in 3-D kinematics were calculated using the adjusted coefficient of multiple correlation. Our results indicate that humans walk with a more stable pelvis than chimpanzees, especially in tilt and rotation. Both species exhibit similar magnitudes of pelvis list, but with segment motion that is opposite in phasing. In the hind limb, chimpanzees walk with a more flexed and abducted limb posture, and substantially exceed humans in the magnitude of hip rotation during a stride. The average stride-to-stride variation in joint and segment motion was greater in chimpanzees than humans, while the intraspecific variation was similar on average. These results demonstrate substantial differences between human and chimpanzee bipedal walking, in both the sagittal and non-sagittal planes. These new 3-D kinematic data are fundamental to a comprehensive understanding of the mechanics, energetics and control of chimpanzee bipedalism.

The human iliotibial band is specialized for elastic energy storage compared with the chimp fascia lata

“…We found that the greater MTU length changes and greater mass-specific force-generating capacity of the human TFL result in greater peak strains in the human anterior ITB than the chimp anterior FL. The anterior ITB in humans stretches more than the anterior FL in chimps because humans walk with greater hip flexion/extension excursion than chimps (O'Neill et al, 2015). Contrary to our hypothesis, peak strains in the posterior ITB and posterior FL are similar in our models.…”

“…7). However, because humans extend their hips more than chimps during bipedal walking (∼45 deg range in humans, from −20 deg extension to 25 deg flexion, versus ∼25 deg range in chimps, from 25 to 50 deg flexion; O'Neill et al, 2015), human ITB MTUs undergo substantially greater length changes than chimp FL MTUs throughout the gait cycle (Fig. 6).…”

“…While moment arms were measured about one joint axis, the other joints were secured at the approximate joint positions found in midstance during bipedal walking (hip flexion, 35 deg; hip rotation, 0 deg; hip adduction, −15 deg; knee flexion, 45 deg) (O'Neill et al, 2015). Lengthening excursion versus joint angle data were fitted with a fourth-order polynomial and the derivative of the polynomial was averaged across trials to estimate the moment arm.…”

Laetoli footprints reveal bipedal gait biomechanics different from those of modern humans and chimpanzees

“…The two chimpanzees studied in these experiments walk bipedally with a more flexed lower limb posture at foot strike than modern humans (approx. 458 of hip flexion and 258 of knee flexion [24]). As such, the relatively shallow toe depths of the Laetoli G1 footprints are in fact compatible with a form of bipedalism involving a more flexed limb posture than is observed in the normal gait of modern humans.…”

“…Kinematic analyses were not conducted in this particular set of chimpanzee experiments, due to logistical constraints and because bipedal hind limb kinematics of these two chimpanzees are already known from other studies [24].…”