Research Interests

The broad objective of my research is to gain a fuller understanding of the control systems human use to generate natural movements and to maintain posture. Proper control of movement and posture is essential in every day human life. For most, this motor control is effortless and automatic and taken for granted; however, the complexity and importance of this control system is very apparent when dealing with people suffering from neuromuscular disabilities. Stroke survivors display poor postural control and difficulty generating coordinated movements; spinal cord injury survivors lack the ability to control their limbs; amputees have limited control of their prosthetic limbs.

Maintenance of Posture

People rely on multiple mechanisms to maintain the posture of their limbs and joints. Co-contracting one's muscles will increase the mechanical stiffness of the joint and is an effective way of maintaining said joint and limb in the desired position. However, this mechanism is not energy efficient, and people will tire of this strategy quickly. Rather, other more energy efficient mechanisms can be used, such as reflexes and voluntary intervention. It is likely that the exact contribution of each of these three mechanism will depend on the task and the environment. I hope to answer these questions by designing experiments that systematically alter the task and the environment and use system identification to quantify mechanics, reflexes and voluntary responses.

Generation of Movement

Much is known about the role of joint and limb mechanics in the maintenance of posture; in comparison little is known about the role of joint and limb mechanics in movement. There are two major challenges limiting the investigation of the role of joint and limb mechanis during movements. The first is the ability to perturb the limb or joint while the subject performs natural movements. The second challengs is producing reliable measures of the state of the joint during highly variable movements. By designing experiment that include realistic and repeatable movements, I aim to estimate how the mechanics and reflexes change during these movements.

System Identification

To investigate the human motor control system, I will use system identification techniques. In particular, I will rely on non-parametric techniques. These are especially valuable in estimating physiological systems as, often, the structure of the underlying system is unknown. Furthermore, since physiological systems are rarely stationary, I will develop techniques that can accurately estimate systems where both the structure of the system and the time-course of non-stationarity are not fully known.