Mechanistic and Physiological Aspect |
Obstacle clearance and prevention from falling in the bipedally walking Japanese monkey, Macaca fuscata
1 Department of Veterinary Physiology, Yamaguchi University, Yamaguchi 753-8515, Japan
2 Department of Biological Control System, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
3 Department of Physiology, Kinki University School of Medicine, Osaka-Sayama 589-8511, Japan
Address correspondence to: F. Mori. Tel: (+81) 83 933 5884; Fax: (+81) 83 933 5884. Email: morif{at}yamaguchi-u.ac.jp
Background: studies are needed which consider CNS-controlled strategies for accommodating perturbed bipedal (Bp) posture and walking.
Objective: to demonstrate the suitability of the Japanese monkey, Macaca fuscata, for the above purpose.
Setting and subjects: three adult monkeys were operantly trained to use Bp-walking on a moving treadmill belt. On one side of the belt, a rectangular adjustable-height obstacle confronted the ipsilateral leg every 4–6 steps, as determined by belt speed.
Methods: animal posture and walking patterns were captured and digitized by two high-speed video systems. Frame-by-frame analyses of side- and back-view kinematics were obtained.
Results: the monkeys learned quickly to proactively clear the in-coming obstacles by use of a flexible hip-knee-ankle flexion strategy. This featured an appropriate postural adjustment and leg trajectory. In cases where a monkey failed to clear the obstacle, it promptly adopted a defensive posture to avoid falling. There was then a quick return to a posture that allowed the resumption of a Bp gait.
Conclusions: when Bp posture and gait are perturbed in a non-human primate model, the prompt adjustment of a flexible hip-knee-ankle flexion strategy and a defensive postural adjustment act together to prevent a fall and enable the speedy resumption of normal Bp posture and gait.
Keywords: bipedal locomotion, obstacle clearance, stumbling, anticipatory, reactive adjustments