Meeting Abstract
The mechanics and control of bipedal locomotion is well studied on level ± 10 deg slopes. However, more-extreme slopes are ecologically relevant for many ground-dwelling birds, including chukar partridge (Galliformes). Such birds are understood to routinely use wing-assisted incline running (WAIR) when ascending steep slopes (> 60 deg), but their methods for descending steep slopes are essentially unknown. To improve understanding of mechanisms of hindlimb control while descending steep slopes, we used high-speed video to measure hindlimb kinematics of chukar (n = 4) walking on slopes ± 35 deg. We hypothesized that the hallux would be the first point of first contact only during descent to facilitate passive arrests. However, the hallux was the point of first contact at every slope condition. Significant changes in kinematics occurred at steep angles, revealing a broader repertoire of body posture and hindlimb movement than would otherwise be indicated if our study was limited to shallower slopes. Knee, ankle, and foot excursion changed significantly over the different slopes. Maximal angles of the knee, ankle, and foot changed significantly with slope. Minimum joint angles did not change significantly except for the knee.
