 Pain initiates a stress response that increases sympathetic output and leads to autonomic imbalance. Heart rate variability HRV is a easy to perform, valid measure of autonomic function. HRV biofeedback HRV-B is a novel biobehavioral procedure in which patients learn to restore autonomic balance by developing HRV Coherence. Patients in HRV Coherence have improved mood and cognition. The investigators pilot study showed that HRV-B alleviated chronic pain and stress among Veteran Pain Clinic patients. HRV-B thus has a pivotal role in managing pain. The proposed project is a randomized, sham-controlled, biobehavioral intervention with HRV-B to test the hypotheses that HRV-B increases HRV coherence and reduces pain, stress, fatigue, insomnia and depression and improves sleep, activity, and cognition in Veterans with chronic neuromuscular pain. The investigators hypothesize that HRV-B will 1 reduce self-reported pain and stress ratings, 2 improve objective measures of actigraphic sleep parameters sleep latency, duration, efficiency, fragmentation, restactivity rhythms dichotomy index, interdaily stability and cognitive function reaction time, attention; and 3 alleviate self-reported fatigue and depression symptoms. Patients from two groups will be randomized to the investigators previously established HRV-B or sham protocol n40 each, and will complete a baseline assessment, 6 weekly training sessions, a post-training assessment, and 4-week and 8-week follow-up evaluations post-training. Portable, hand-held, data-logging devices will be used to practice attaining HRV coherence at home by the active HRV-B training group, while those in the sham training group will get a stress squeeze ball. Standard methods will quantify HRV coherence and other HRV measures, and validated instruments will be used to assess pain, stress, fatigue, insomnia, depression, and cognitive function. Wrist actigraphy will be used to objectively characterize insomnia via continuous recordings collected 24-hrsday over three 1-week periods pre-training, post-training, and at the 4 week follow-up assessments. Tests measuring attention and reaction time will assess changes in cognitive performance. Data analyses will apply linear models for repeated measures to evaluate the effect of HRV-B on study outcomes, and on treatment persistence, after adjusting for confounding factors. This study will be the first to examine HRV-B for pain management among Veteran chronic pain patients. 