Meeting Abstract
The majority of locomotion studies have focused on parasagittal motion and all but ignored any forces or movement in the frontal plane. Our previous research has shown that grizzly bears produce higher medial ground reaction forces (lateral pushing from the animal) than would be expected for an upright mammal, suggesting frontal plane movement is an important aspect of their locomotion. We conducted an inverse dynamics analysis, of sagittal and frontal planes, on ground reaction forces and position data from three high speed cameras of four adult female grizzly bears. Speeds were separated into three ranges, which approximately correspond to gait transitions. Average work produced by the forelimb was 0.18-0.45 W kg-1, with the lowest value at the middle speed range. At all speeds the shoulder produces positive net work in the sagittal plane, while the wrist absorbs energy. This pattern is reversed in the frontal plane. In both planes, at all speeds, the elbow has variable but low values of net work. The average frontal elbow angle across all speeds is 154° and the frontal angle of the foot relative to the forearm is 31°. The distribution of power in the sagittal plane, highest in the shoulder and lowest in the elbow, is similar to what has been reported for the forelimb of horses. However, the frontal joint angles for the elbow and wrist, as well as the lateral power produced at higher speeds, suggest a substantial proportion of energy produced by the limb is lost in lateral propulsion and not used to propel the animal forward. A detailed musculoskeletal model will be created to identify specific muscle contributions of the limb movements.
