Heartrate Variability (HRV):

Heartrate variability (HRV) measures beat-to-beat variations in heartrate as part of biofeedback training that activates and calms the nervous system. It feeds back heartrate data during slow breathing—so breathing matches heartrate patterns. It’s known a healthy heart’s rhythm at rest is surprisingly irregular. HRV shows physiological resiliency and behavioral flexibility to adapt to stress and environmental demands. Both large and too little variation can relate to chronic pain, anxiety, and depression. When combined with cognitive behavioral therapy (CBT) and/or virtual reality therapy (VRT), biofeedback helps manage anxiety and tension, elevate mood, and improve sleep, according to decades of evidence.