What Does a Biofeedback Machine Do?
Imagine if your car had no speedometer. You might have a basic idea of how fast you are going, by say, comparing your speed to other cars. However, without continuous, accurate feedback on your speed, it may be difficult to adjust to the ever-changing road environment.
In the same way, we can have a basic idea of our emotional and physiological state, but a biofeedback machine gives us detailed, real-time information about these states. With this information, we can take action to improve our stress resilience, performance, and overall health. At its core, biofeedback harnesses the power of the mind-body connection, thereby strengthening the link between our thoughts, emotions, and physiological responses.
What is biofeedback?
Biofeedback is a mind-body tool that uses biosensors to allow patients to consciously control bodily functions that are normally involuntary. By measuring physiological parameters in real-time, biofeedback machines allow a person to shift these parameters in a healthy direction to improve performance and overall well-being.
In 2008, three professional organizations representing the field of biofeedback agreed on a standard definition of biofeedback. The consensus definition was as follows:
“Biofeedback is a process that enables an individual to learn how to change physiological activity for the purposes of improving health and performance. Precise instruments measure physiological activity such as brainwaves, heart function, breathing, muscle activity, and skin temperature. These instruments rapidly and accurately “feed back” information to the user. The presentation of this information—often in conjunction with changes in thinking, emotions, and behavior—supports desired physiological changes. Over time, these changes can endure without continued use of an instrument.”
In this way, biofeedback devices hold a mirror up to a person’s internal states, allowing greater self-awareness of maladaptive physiological responses. Ultimately, this self-awareness in the form of feedback leads to the development of self-regulation skills to adjust and correct these responses. Over time, these self-regulation skills encourage healthier thoughts, feelings, and behaviors that can be applied outside of the context of the biofeedback session.
What a biofeedback machine does
During a biofeedback session, the machine sensors or electrodes are attached to the body to measure specific physiological activities. These physiological activities can include:
- Muscle tension
- Blood pressure
- Heart rate
- Heart rate variability
- Respiration rate
- Skin temperature
- Brain waves1
These biosensors then relay this information in real-time back to the user on an audiovisual display.2 The signals are converted into a visual or auditory cue, such as an image, video, beep, or flash of light. The biofeedback therapist will then guide the patient through mental and physical exercises to manipulate these cues towards healthier values.
These exercises can include progressive muscle relaxation, body scanning, breathing techniques, mindfulness meditation, and guided imagery. In general, the aforementioned parameters are all proxy measures of sympathetic (“fight-or-flight”) arousal, a maladaptive bodily state that is involved in a variety of stress-related conditions. By engaging in relaxation techniques alongside the immediate feedback of these parameters, the patient can learn to optimize their internal states to make lasting, beneficial physiological changes.
Types of biofeedback devices
Depending on a person’s symptoms or condition, biofeedback therapists will use different modalities in order to measure different bodily functions. Here, we will overview the most common biofeedback machines and what they are used for.
Electromyographic (EMG) biofeedback
EMG feedback uses surface electrodes placed on a patient’s muscles to measure muscle tension and activity. Clinicians may also insert needles intramuscularly to minimize nearby muscular “cross-talk” and pick up signals from deeper muscles. Changes in muscle tension are fed back to the patient in the form of auditory or visual cues. Depending on what’s being treated, this feedback can be used to increase muscle activity in weak muscles or decrease activity in overactive or spastic muscles.3
EMG feedback is most commonly used in the context of neurological and musculoskeletal rehabilitation. Specifically, it has been used to treat:
- Back pain
- Pelvic pain
- Tension headache
- Temporomandibular joint (TMJ) dysfunction
- Spasmodic torticollis
- Injuries (physical rehabilitation)
- Urinary incontinence
Electroencephalographic (EEG) biofeedback
Also known as neurofeedback, EEG feedback measures the brain’s electrical activity using high-gain amplifiers. Surface electrodes are placed on the scalp and forehead to measure specific brainwave frequencies. During training, the patient’s brain is nudged towards a desired pattern of brain activity with the help of positive or negative sensory feedback. Typically, the goal of neurofeedback is to train the patient to generate “alpha” brain waves, which are associated with relaxation. Neurofeedback can be used to treat a wide array of conditions and disorders, including:
- Attention deficit hyperactivity disorder (ADHD)
- Post-traumatic stress disorder (PTSD)
- Obsessive-compulsive disorder (OCD)
- Learning disabilities
- Brain injuries
- Seizure disorders.
Galvanic skin response (GSR) biofeedback
Also known as electrodermal activity (EDA) biofeedback, GSR biofeedback measures changes in skin conductivity which can signal variations in emotional arousal. Typically, the sensors are placed on the fingers or palm of the hand and wrist. When skin conductance increases, this may increase the pitch of an auditory feedback cue, while decreases in skin conductance may decrease the pitch. Electrodermal activity is also measured with lie detectors since changes can reflect increased anxiety levels around the act of lying.
Psychotherapists may use GSR biofeedback to help clients become more aware of their emotions.4 In addition, biofeedback therapists use GSR biofeedback to treat:
- Excessive sweating
While ZYTO technology uses galvanic skin response in a similar way, the biofeedback is in the form of information that can be used to proactively improve wellness. ZYTO technology, including the Hand Cradle GSR device, is not diagnostic and isn’t used to treat, prevent, mitigate, or cure any disease or medical condition. Instead, this technology provides information that a person can use to make better decisions about their health and wellness.
Thermal biofeedback uses sensors, usually placed on the hands or feet, to measure skin temperature. Skin temperature is an accurate measure of relaxation, as low temperatures are indicative of sympathetic arousal. With the help of feedback and relaxation techniques, this method allows the patient to raise their skin temperature. In turn, this increases blood flow to specific regions of the patient’s body.
Thermal biofeedback has been used successfully to treat:
- Tension headaches
- Raynaud’s disease (insufficient blood flow to peripheral areas in response to cold or stress)
Heart rate variability (HRV) biofeedback
HRV biofeedback helps train people to increase their heart rate variability to improve psychological and physiological functioning. Heart rate variability refers to the variation in time between each successive heartbeat. A high HRV implies that there is high beat-by-beat variance, while a low HRV signals that there are small variations in the time between each heartbeat. Low HRV is associated with increased susceptibility to stress, while high HRV is associated with increased stress resilience and optimal parasympathetic response.5
HRV biofeedback is well-researched and has been found to be helpful for:
- Abdominal pain
- Chronic obstructive pulmonary disease (COPD)
- Heart disease6
Who uses biofeedback machines?
Biofeedback is a highly multidisciplinary practice in health care. A wide variety of health professionals provide biofeedback training. This includes, but is not limited to:
- Social workers
- Physical therapists
- Occupational therapists
Qualified biofeedback practitioners can be found on the Association for Applied Psychology and Biofeedback website. The non-profit organization called the Biofeedback Certification International Alliance (BCIA) provides certification for prospective biofeedback practitioners.
Biofeedback can be performed by these practitioners at various office settings, including biofeedback clinics, hospitals, medical clinics, and physical therapy centers. Increasingly, in-home biofeedback machines and wearables are available for home use.
In either case, biofeedback training requires the patient to engage in regular practice between training sessions. Sessions typically last 15-60 minutes, and it may take 10 or more sessions to see a benefit, depending on the condition being treated. As opposed to a multitude of other treatment modalities, biofeedback can improve our health and performance without the risk of undesirable side effects.
1. Labbé, E. E. “4 – Biofeedback” in Assessment and Therapy. Specialty Articles from the Encyclopedia of Mental Health (2001): 37–45.
2. Yu, B., M. Funk, et al. “Biofeedback for Everyday Stress Management: A Systematic Review.” Frontiers in ICT 5 (2018).
3. Giggins, O. M., U. M. Persson, & B. Caulfield. “Biofeedback in rehabilitation.” Journal of Neuroengineering and Rehabilitation 10, no. 60 (2013).
4. Frank, D. L., L. Khorshid, et al. “Biofeedback in medicine: who, when, why and how?” Mental Health in Family Medicine 7, no. 2 (2010): 85–91.
5. Lehrer, P. M., & R. Gevirtz. “Heart rate variability biofeedback: how and why does it work?” Frontiers in Psychology 5 (2014): 756.
6. Moss, D. “Heart rate variability and biofeedback.” Psychophysiology Today: The Magazine for Mind-Body Medicine 1 (2004): 4-11.