Acute Effects of a Single-Session Body Awareness Intervention on Cortical Activity and Interoceptive Accuracy

Body awareness is a multidimensional construct that involves conscious perception of posture, breathing, muscle tone, movement, balance, contact, and internal bodily sensations. It is closely related to interoception - the perception and interpretation of physiological signals arising from within the body. Prior research suggests that body-awareness-based approaches, such as Basic Body Awareness Therapy, can positively influence body awareness, body attitude, and psychophysiological function in various clinical populations. However, few studies have examined the acute neurophysiological effects of a single body awareness session in healthy young adults using portable, low-channel EEG systems, and the relationship between EEG changes and interoceptive accuracy remains insufficiently explored.

This study is designed as a two-arm, parallel-group, randomized controlled trial. Participants will be randomly assigned in a 1:1 ratio to either an intervention group or a control group. Randomization will be generated by an independent researcher not involved in data collection or intervention delivery, using a computer-based random number method; group allocation will be concealed using sequentially numbered, opaque, sealed envelopes opened only after baseline measurements are completed. Due to the nature of the intervention, participants and the person delivering the session cannot be blinded; however, researchers involved in EEG signal processing and interoceptive accuracy scoring will be blinded to group assignment where possible.

The intervention group will receive a single, approximately 30-minute structured body awareness session based on Basic Body Awareness Therapy principles, consisting of preparatory orientation, supine body scanning and contact awareness, breath awareness, slow symmetrical movement awareness, seated midline/postural awareness, standing weight-shift awareness, and a closing integration period. The control group will undergo a quiet/neutral resting session of equal duration and in the same environment, without any body-awareness-related instructions, in order to control for effects attributable to time, environment, rest, or eye closure alone.

In both groups, resting-state EEG will be recorded before and after the session using an 8-channel wireless EEG device (Enobio 8) at a 500 Hz sampling rate, following the international 10-20 system, with electrode sites covering frontal, sensorimotor, and parietal regions (Fz, FCz, Cz, C3, C4, Pz, P3, P4). EEG data will be preprocessed using standard steps including band-pass filtering (1-45 Hz), 50 Hz notch filtering, independent component analysis (ICA), artifact rejection, and common average referencing. Absolute and relative power in the delta, theta, alpha, beta, and gamma frequency bands will be calculated, with particular attention to frontal theta, alpha, and gamma activity, given their proposed associations with attention, internal focus, and relaxation.

Interoceptive accuracy will be assessed before and after the session using a heartbeat perception task based on the Schandry method, in which participants silently count perceived heartbeats over defined time intervals without taking their pulse; actual heartbeats will be recorded physiologically over the same intervals, and a normalized interoceptive accuracy score will be derived from the agreement between perceived and actual counts.

The primary outcome is the pre-to-post change in EEG frequency band power. The secondary outcome is the pre-to-post change in interoceptive accuracy score, and the relationship between EEG-based changes and interoceptive accuracy changes will also be examined. Sample size was determined via power analysis (G*Power 3), based on effect sizes reported in prior heartbeat-evoked potential research, yielding a target of 42 participants per group (84 total) at α = 0.05 and 80% power, including an allowance for a 20% dropout rate. Statistical analysis will include mixed-design analyses (e.g., two-way mixed ANOVA or linear mixed models) to evaluate group × time interactions for EEG outcomes, and correlational analyses (Pearson or Spearman) to examine associations between EEG and interoceptive accuracy changes, with appropriate corrections for multiple comparisons across channels and frequency bands. The study will be conducted and reported in accordance with CONSORT guidelines for randomized controlled trials.