We all react to stress differently in our bodies. Some people experience it most in their heart (e.g., hypertension), others in their gut (e.g., IBS), others in their muscles (e.g., chronic muscle tension), etc. Peripheral biofeedback training utilizes technology to monitor normally automatic bodily functions and train people to acquire voluntary control of those functions. Gaining self-regulatory capabilities over our psychophysiological processes allows us to alter those processes, reduce our stress reactivity, and improve our overall health. Here at NeuroGrove, we will conduct a psychophysiological assessment to see where you personally store your stress. We can then provide the specific type of biofeedback that would be most beneficial for you. Examples include electromyographic (EMG) biofeedback, skin temperature training, and heart rate variability biofeedback.


Heart rate variability (HRV) biofeedback is a relatively new self-regulation technique that trains people to change the dominant rhythms of their own heart activity. HRV is a measure of balance within your autonomic nervous system, which is involved in both our stress (i.e. sympathetic) and relaxation (i.e. parasympathetic) responses. Effective emotional regulation depends on being able to flexibly and appropriately adjust this physiological response to a changing environment. Research has shown that people with higher levels of HRV tend to have better levels of physical, mental, and emotional wellness. Thus, HRV biofeedback strives to improve this balance and flexibility within the autonomic nervous system by increasing HRV.

human body nervous system

Breathing air into the lungs temporarily gates off the influence of the parasympathetic nervous system on heart rate, producing a heart rate increase. Breathing air out of the lungs reinstates parasympathetic influence on heart rate, resulting in a heart rate decrease. This rhythmic fluctuation in heart rate is healthy, and the higher the variability, the healthier your heart.

Multiple connections also exist between the heart and the brain. The two are in constant communication and each exerts an influence on the other. One pathway involves the central autonomic network (CAN), which involves cortical, limbic, and brainstem components of the brain. The CAN assists emotional regulation by adjusting physiological arousal (e.g. heart rate) to appropriately match internal and external circumstances. Heart rate variability (HRV) is a measure of how well the CAN is functioning and whether the autonomic nervous system is being effectively regulated. When HRV is low, people tend to get stuck in an excessively sympathetic (i.e. stressed and aroused) or parasympathetic (spaced out, disconnected, fatigued, and emotionally numb) state, or constantly swing between the extremes of the two without finding a healthy balance.

In turn, the nervous system in the heart can also exert influences upon the brain. For example, baroreceptors (i.e. stretch receptors) on the blood vessels of the heart detect increases/decreases in blood pressure and send that information up to the medulla of the brainstem, which continues to send messages up to the limbic system. As a result, an increase in heart rate and blood pressure can ultimately send a message to the brain that there is a threat in the internal or external environment, leading the brain to trigger a stress response throughout the body.


There are different styles of HRV biofeedback training. Here at NeuroGrove, we use a modality called Resonant Frequency Training.

The heart resonates like a musical instrument. Current research suggests that every individual has a “resonant frequency” at which heart rate variability is the greatest, and this resonant frequency can be measured with biofeedback instruments. Just as hitting the string of a violin just right makes the loudest, most beautiful tone, so “hitting the heart strings” just right produces the highest and healthiest levels of HRV. While everyone is unique, this resonant frequency is most often produced when a person is breathing in a calm, smooth manner at a rate of about 4 to 7 breaths per minute. In our first training session, we will find the exact breathing rate that is ideal for you and produces the highest levels of HRV.

EKG results on ipad
Functional Medicine graphic


In addition to HRV biofeedback, we also utilize other forms of peripheral biofeedback, such as electromyographic (EMG; muscle) biofeedback and skin temperature biofeedback to address imbalances within the body and improve its response to stress. It is common for our muscles to tense and tighten when faced with stress and anxiety. Over time, however, we often start chronically holding that tension, especially in the shoulders and jaw. This not only contributes to painful muscle tension and headaches, but it can also send messages back to the brain that there must be a threat to worry about, triggering a stress response.

Biofeedback with EMG temperature

EMG biofeedback involves training the muscles to relax and be more flexible while also balancing the nervous system. We start by attaching sensors to the targeted muscle group, which allow us to measure real-time muscle activity. Then, using auditory and visual feedback, the brain and body receive data on the level of tension and are rewarded when the tension is reduced. We then pair this with tools and techniques to aid relaxation. With regular training, clients gain better awareness around how their bodies are storing stress and ways to promote relaxation and balance. Over time, we can engrain new patterns with the nerves that innervate our muscles, leading to more lasting effects.

When we experience chronic or excessive stress, our nervous system is tipped into a sympathetic (i.e., fight-or-flight) state. In such a state, our brain and body prepare for an immediate response to a direct threat to our life or wellbeing. As part of this response, our body constricts the blood vessels to divert blood out of our extremities and into our heart and larger muscle groups, allowing us to fight harder and run faster. As a result, the temperature in our fingers and toes tends to drop. In contrast, when the body is relaxed and calm, skin temperature increases. Interestingly, with the help of technological feedback, we can consciously control this response and increase the temperature within our fingertips. This can not only assist with physical challenges such as Raynaud’s syndrome, but can also send messages back to the brain that we are safe and thus reduce anxiety and stress reactivity.

Temperature biofeedback helps provide us with greater awareness around the nervous system’s level of activation by using a temperature sensor attached to the finger. We then guide the client through a variety of relaxation exercises, such as breathwork and autogenic phrases, to help the body enter into a calmer state. As the parasympathetic system is activated and the body becomes more relaxed, the skin’s temperature begins to rise. Like with other forms of biofeedback, clients learn how to gain conscious control over the nervous system and can more easily drop into relaxation and balance.


In HRV biofeedback, special instruments are used to read your breathing patterns and heart rhythm. We will place three electrocardiogram (EKG) sensors on your forearms to detect the activity generated by your heart. A respiration sensor (i.e. “breathing belt”) placed around your stomach will also detect outward movement as you inhale and inward movement as you exhale. This equipment can measure both the depth and rate of your breathing.

During HRV biofeedback, you will follow a breathing pacer that has been set to your individual resonant frequency. Your heart and breathing activity will be displayed on a computer screen in real time to help you learn to produce healthier levels of variability. Alternately, this can also be displayed in the form of a movie that fades/zooms in as your HRV increases and fades/zooms out when your HRV decreases. This helps you know when you are “on the right track” and trains your brain and heart to continue producing healthy levels of HRV.


Yes! HRV biofeedback has been found to be a very low-risk intervention with very few potential side effects. The sensors placed on your forearms simply read your heart’s electrical activities–they do not put any electrical or other forms of stimulation into your body. We are enticing your heart to change because we are rewarding “good behavior,” but we are not inducing any activity ourselves. The most common side effect is feeling a bit “tired” after training, which may be the result of relaxing your nervous system. It is also possible to “over-breathe,” leading to minor symptoms like lightheadedness. We will teach you to breathe appropriately and check in with how you are feeling throughout each session to prevent this from happening. If it does occur, however, any related symptoms usually subside as soon as you start breathing normally again.