Speed modulation in hylobatid bipedalism: a kinematic analysis

Area of Science:

• Primate locomotion
• Biomechanics
• Evolutionary biology

Background:

• Gibbons (hylobatids) are highly arboreal apes.
• Previous research indicates rare unsupported phases and low stride frequencies in gibbon bipedalism.
• Arboreal locomotion likely influences terrestrial bipedal gait.

Purpose of the Study:

• To investigate the mechanisms gibbons use to modulate locomotor speed during bipedalism.
• To analyze the 3D kinematics of gibbon bipedal locomotion.
• To compare gibbon bipedalism with that of humans and bonobos.

Main Methods:

• Recorded spontaneous bipedal locomotion of four white-handed gibbons using an instrumented walkway and four synchronized cameras.
• Digitized video images to quantify 3D kinematics.
• Analyzed spatiotemporal and kinematic gait variables and their relationship with speed.

Main Results:

• Gibbons primarily increase stride length to achieve higher locomotor speeds.
• Key speed-modulating mechanisms include hip and ankle excursion and coupled knee-ankle extension at toe-off.
• Gibbons exhibit a bipedal bouncing gait across most speeds, lacking a distinct gait transition like humans.

Conclusions:

• Arboreal constraints influence gibbon bipedal gait but do not prevent a bouncing gait on the ground.
• Low variability in gibbon hind limb joint angles may be linked to arboreal adaptations.
• Gibbons effectively modulate speed through stride length and joint movements, despite arboreal influences.