The Gate Control Theory (Melzack and Wall, 1965, ) postulates a pain transmission gate located in the substantia gelatinosa region of the dorsal horn of the spinal cord. The theory states that pain transmission through this gate is altered by sensory nerve input to this region. Subsequent research since 1965 has supported much of the Gate Control Theory and has added new dimensions to it (Wolf, ; 1984; Fields and Levine ; 1984). TENS pulse frequencies between 75 Hz and 150 Hz (cycles per second or pulses per second) are recommended to activate this mechanism (Mannheimer and Lampe, ; 1984). This theory would explain pain reduction only during flow of current.