Table 4 Biofeedback & Neurofeedback variable definitions and abbreviations

EMG

Root mean square (RMS) amplitude of EMG

This parameter measures the average amplitude of the EMG signal over a given time period. Increased RMS amplitude has been associated with increased muscle tension and pain.

Median frequency (MF)

Median frequency (MF): This parameter measures the frequency at which half of the power in the EMG signal is contained. Decreased MF has been associated with increased muscle fatigue and pain.

Frequency band power

Frequency band power: This parameter measures the power of the EMG signal in different frequency bands. Increased power in the high frequency band (above 100 Hz) has been associated with increased muscle tension and pain.

EKG (ECG)

Heart rate

Heart rate is the frequency between the beginning of one pulse to the beginning of the next and is expressed in a specific time window (usually one minute).

Heart rate variability (HRV)

It describes the normal changes in heart rate from one beat to the next. HRV is closely related to emotional arousal: HRV has been found to decrease in critical situations and emotional stress (meaning the heart rate is more consistent). It has also been observed that people with more daily stress and worries have lower HRV.

SCR (GSR)

Root mean square (RMS) of GSR

This parameter measures the change in skin conductance in response to a stimulus, such as a painful or anxiety-provoking event. Increased SCR has been associated with increased sympathetic nervous system activity and pain or anxiety.