Pulling on objects in the world (e.g., opening a door) is a common activity of daily living that requires people to use their arms effectively, often while maintaining a standing posture. Such actions, which are readily performed by adults are deceptively simple. Pulls made while standing actually require a complex and precise coordination of many muscles and body segment motions for the person to achieve the focal goal of pulling, and still maintain balance. Research has shown that postural adjustments (body motions and muscle activity) accompany pulling movements made by free-standing individuals. However, neither the precise function of these postural movements nor the neural processes by which they are coordinated with arm movements are very well understood. This research program will shed light on how postural adjustments are coordinated with arm movements. The studies will systematically vary the amount of physical support and expectancy factors. The effect of these factors on body motion and balance, on pulling forces, and on muscle activity in the arms and legs will yield new insights into the functional and neural processes which coordinate postural adjustments with voluntary pulling movements. This resezrch will contribute significantly to fundamental knowledge about the control of posture and movement.
