Effect of Stretching on the Electroencephalography of People With Irritable Bowel Syndrome

Introduction Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterized by chronic abdominal pain and altered bowel habits without structural abnormalities. Irritable bowel syndrome affects approximately 9.3% of the Japanese population based on Rome III criteria, with higher prevalence observed in younger adults, and is associated with significant impairments in quality of life. Its multifactorial pathophysiology involves dysregulation of the brain-gut-microbiome axis, with altered brain activity, such as reduced alpha and increased beta power on electroencephalography (EEG) during eyes-closed resting states. Although nonpharmacological interventions such as abdominal and trunk stretching have demonstrated potential in reducing psychological stress markers, their neurophysiological effects in individuals with IBS remain poorly characterized. This study aimed to investigate the neurophysiological and somatosensory effects of a brief abdominal stretching intervention in patients with IBS. We hypothesized that stretching would (1) increase frontal alpha power and (2) increase somatic sensory and pain thresholds. Methods Fourteen adult males (mean age, 23.5 ± 1.2 years) with symptomatic IBS based on the Japanese version of the IBS Severity Index completed an Irritable Bowel Syndrome Quality of Life measure, followed by baseline assessments of sensory and pain thresholds and a 10-minute resting-state EEG. Participants performed a 4-minute supine trunk rotation stretching protocol involving bilateral 1-minute holds repeated twice per side until mild discomfort was perceived. Alpha power (8-12.8 Hz) from EEG recordings and sensory and pain thresholds were statistically analyzed using paired-sample Student's t-tests to compare pre- and post-intervention data. Statistical significance was set at p < 0.05. Results Alpha power in the frontal regions significantly increased after the stretching intervention (t (13) = 3.28, p < 0.01, d = 0.31). Sensory thresholds also increased significantly after the intervention (t (13) = 2.76, p = 0.02, d = 1.04), while pain thresholds showed no significant change (t (13) = 0.98, p = 0.35, d = 0.37). Conclusions The increase in alpha power supports the hypothesis that stretching induces neurophysiological relaxation by modulating central sensory processing. The elevation in sensory thresholds may reflect reduced somatosensory hypersensitivity; the lack of change in pain thresholds suggests that the intervention did not substantially affect nociceptive processing, possibly due to limited stimulation intensity or duration. Collectively, these findings suggest that stretching may serve as a viable self-management strategy for IBS by modulating both EEG activity and somatosensory indices. Further randomized controlled trials are warranted to validate these effects and investigate their potential association with autonomic nervous system dynamics.