At the second session, the participant will be directly given biofeedback for cardiac variability, and instructed to increase the amplitude of heart rate fluctuations that occur in conjunction with respiration. The feedback will be given in several forms. One is using a beat-to-beat cardiotachometer display, superimposed on a measure of respiratory activity taken from a strain gauge. The participant will be instructed to breathe approximately in phase with heart rate changes, with the goal of maximally increasing amplitude of RSA. In another display, the participant will be shown a moving frequency analysis of heart rate, within the band of .005-.4 Hz. The display will be updated approximately every second, and reflects the frequency of heart rate fluctuations within the past 30 seconds. The participant will be instructed to increase the spectral power peak that occurred at approximately resonant frequency. At the beginning and end of this and every biofeedback session participants will be asked to rate their pain, muscle stiffness, fatigue, mood and cognitive processes (memory and concentration) on a verbal scale of one to ten.