Impedance control is a popular method of controlling the dynamic response a robot has to external forces. The advantage of such a control paradigm is the ability to manipulate in both unconstrained and constrained environments. Unlike hybrid control methods that attempt to control forces and motions in orthogonal directions, impedance control consists of a single control law that accommodates external forces. One problem associated with such a controller is the selection of the robot's target impedance. This paper illustrates, through analysis and experimentation, the shortcoming of improper target impedance selection. The integration of a real time estimate of the robot's environment with the impedance controller resolves this problem. Experimental results illustrate improved performance during the transition from unconstrained to constrained manipulation.