Biofeedback

Biofeedback turns quiet body signals into something you can see or hear. An instrument measures a signal such as heart rhythm, breathing, or muscle tension and shows it back in real time, as a line on a screen, a number, or a tone. The biofeedback field defines it as a process that helps a person learn to change their own physiological activity to improve health and performance, using instruments that feed back what the body is doing (Association for Applied Psychophysiology and Biofeedback, n.d.).

At its center is a loop. A signal leaves the body, a sensor reads it, and the reading comes back to someone who can respond. That someone can be you, the practitioner, or the instrument itself, and each version of the loop does different work.

Three Ways the Loop Runs

• Biofeedback training: the reading comes back to you, and you learn to change it, for example by slowing your breath while you watch your heart rhythm respond. This is biofeedback in the strict sense the field uses (Association for Applied Psychophysiology and Biofeedback, n.d.).
• Practitioner feedback: the reading comes back to the person guiding the session, who uses it to decide where to spend time and when to ease off.
• Instrument feedback: the instrument reads the body and adjusts its own output, again and again, as the session goes on. The Electro-Acuscope and Myopulse work this way, and their training materials call the process biofeedback (Dacri, n.d.).

In our microcurrent sessions, the second and third loops run together, and the first can join them whenever the readings are shared with you.

Signals Biofeedback Can Read

• Heart rhythm: the small beat-to-beat changes in heart rate that heart rate variability biofeedback trains.
• Breathing: the rate and depth of each breath.
• Muscle tension: the electrical activity of muscles, read through the skin by surface electromyography (EMG).
• Skin temperature: read by a small sensor resting on the skin.
• Brainwaves: the electrical activity of the brain, read by EEG. Biofeedback with brainwaves is often called neurofeedback.
• Skin conductance: how easily the skin carries a tiny current, which changes with sweat gland activity driven by the sympathetic nervous system (Posada-Quintero & Chon, 2020).
• Tissue impedance: how much the tissue between two contact points resists a very small current. This is the reading the Electro-Acuscope and Myopulse use (Dacri, n.d.).

The first five are the signals named in the field’s own definition of biofeedback (Association for Applied Psychophysiology and Biofeedback, n.d.).

How Heart Rate Variability Biofeedback Works

Your heart speeds up a little as you breathe in and slows as you breathe out. Heart rate variability biofeedback makes that rhythm visible and invites you to slow your breathing until the swings grow large and smooth, like a wave. For most people the swings are largest at about six breaths a minute, and later work refined the average to about 5.5 breaths a minute, or roughly 11 seconds per breath. The best rate differs from person to person; taller people and men tend to need slightly slower breathing. Many people can produce the pattern within a minute, even on a first try (Lehrer & Gevirtz, 2014).

Why that rate? Near six breaths a minute, breathing, heart rate, and blood pressure lock into a steady timing with one another. The baroreflex, the pressure-sensing loop in the aorta and carotid arteries that slows the heart when blood pressure rises and speeds it when blood pressure falls, then amplifies each swing. The best-supported explanation for the benefits of training is that this repeated exercise strengthens the baroreflex. A newer proposal points to signals carried from the body to the brain along the vagus nerve (Lehrer & Gevirtz, 2014).

Biofeedback in a Microcurrent Session

The Electro-Acuscope and Myopulse are microcurrent instruments that listen while they work. According to the system’s training materials, each instrument monitors the impedance of the tissue between two contact points, compares the reading with built-in norms, and shapes its next output from that comparison. The polarity of the probes reverses every two seconds, so the instrument alternates between reading and treating, and its output keeps changing through the session. The materials describe the instruments as self-adjusting (Dacri, n.d.).

The practitioner receives the readings too. Both instruments have digital displays, and the Acuscope also plays tones that change as the reading changes. Operators are trained to use these readouts to find the areas that need attention and to follow change as a session goes on (Dacri, n.d.).

In our sessions, this loop is how tissue response testing works. The instrument’s readings, together with what you tell us about how an area feels and how your body is settling, decide where the session goes. When the tones and numbers are shared with you, you can follow your own readings as they change.

Is this biofeedback? It depends on the definition. In the strict sense the biofeedback field uses, the reading comes back to you so that you can learn to change it (Association for Applied Psychophysiology and Biofeedback, n.d.). The Electro-Acuscope and Myopulse loop runs mainly through the instrument and the practitioner, so it is closer to a self-adjusting stimulator than to biofeedback training. The system’s training materials use the broader sense of the word: a reading from the body that shapes what happens next (Dacri, n.d.). This page uses both senses and says which one it means.

How we use it

In the Three Signals, biofeedback is the thread that ties light, field, and current together. It is how we listen, so a session can follow the person rather than a fixed protocol. We use it for awareness and personalization. It is not a diagnostic test, and it does not detect or treat any condition.

Where the evidence stands

Heart rate variability biofeedback has one of the stronger evidence bases among wellness tools. A meta-analysis of 24 studies with 484 participants found that it was associated with a large reduction in self-reported stress and anxiety (Hedges’ g = 0.83 compared with control conditions), and the authors added that more well-controlled studies are needed (Goessl et al., 2017). A broader review of 58 randomized controlled studies found a small-to-moderate benefit across many outcomes, largest for anxiety, depression, anger, and athletic and artistic performance, and smallest for PTSD, sleep, and quality of life. Effects were larger against inactive comparison conditions than active ones, though significant for both (Lehrer et al., 2020).

Muscle tension biofeedback has its own record. A meta-analysis of 53 outcome studies of biofeedback for tension-type headache found a medium-to-large effect (d = 0.73) that held over an average follow-up of 15 months, and biofeedback did better than headache monitoring, placebo, and relaxation therapies (Nestoriuc et al., 2008).

The Electro-Acuscope and Myopulse have a much thinner record. The studies we found are small and decades old: a double-blind study of students with neck and shoulder trigger points, in which the treated group improved more than the placebo group (Chee & Walton, 1986), and a 1993 review noting that the efficacy of the Electro-Acuscope and two similar devices remained controversial (Dreyfuss et al., 1993). We have not found a study that tests the feedback feature on its own by comparing self-adjusting output with fixed output. The descriptions of what the readings show come from the system’s training materials, and we have not found independent tests of them (Dacri, n.d.).

What the Evidence Shows

Common Questions

Is the Acuscope reading the same as skin conductance biofeedback? Not as far as we know. Both pass a tiny current through the skin and measure how easily it flows. Skin conductance biofeedback is used to follow arousal, because sweat gland activity tracks the sympathetic nervous system (Posada-Quintero & Chon, 2020). The Acuscope reading is described as tissue impedance between two contact points, judged against the system’s own norms (Dacri, n.d.). We know of no study that compares the two.

If I feel calmer, isn’t that enough? Feelings matter, and they are not the whole picture. In a study of 67 people on a five-day nature trip, mood improved while heart rate rose and a measure of heart rate variability fell, the opposite of what the researchers expected (Scott et al., 2021). That is why we ask how you feel and also measure.

Can biofeedback tell what is wrong with me? No. In our sessions it is used for awareness and personalization, not diagnosis. The Acuscope training materials describe readings that locate inflammation or depleted tissue (Dacri, n.d.). We treat those descriptions as the system’s own model, not as a medical finding.

Do I have to learn anything for it to work? Not in a microcurrent session, where the instrument and the practitioner carry most of the loop. Heart rate variability biofeedback is different: it is a skill practiced over time. In one line of research, people who practiced twice a day for about three months showed a stronger baroreflex even before each practice began (Lehrer & Gevirtz, 2014).

Open Questions

• Does the self-adjusting output of the Electro-Acuscope and Myopulse change outcomes compared with fixed microcurrent at the same strength?
• What do the Acuscope and Myopulse readings track in physiological terms: skin moisture, contact pressure, deeper tissue, or a mix?
• Do people who can see or hear their own readings during a session report more calm, or show more physiological change, than people who cannot?
• Does pairing slow-breathing biofeedback with an immersive light and sound environment change results compared with biofeedback alone?

Related Terms

Heart Rate Variability · Baroreflex · Skin conductance · Electro-Acuscope and Myopulse · Microcurrent · TENS · Three Signals · Evidence Gradient

References