The application of optical imaging to other areas of the body is restricted by the limited penetration of light across large thicknesses of tissue. Muscle tissue has been widely investigated using NIRS, although relatively few optical imaging studies have been reported. The forearm muscle has probably been the most frequently studied, the first time by Maris et al. (1994) using a frequency-domain optical topography system to map differences in the hemoglobin oxygenation in finger extensor muscles during exercise. Graber et al. (2000) have used a CW optical tomography system for a series of real-time dynamic arm imaging experiments, and Araraki et al. (2000) and Hillman et al. (2001) have used time-domain systems to measure changes in tissue absorption in response to finger flexion exercise