Neural Contributions to Exercise-Induced Hypoalgesia With Blood Flow Restriction

Exercise-induced hypoalgesia (EIH) is a physiological response characterized by reduced pain sensitivity following physical activity. Several central and peripheral mechanisms have been proposed to explain EIH, including activation of descending inhibitory pathways and peripheral nociceptor modulation. BFR training involves the application of controlled vascular occlusion during low-load exercise and has shown promising results in enhancing both muscle function and pain modulation. This is a single-arm, pre-post experimental study involving healthy adults aged 18-35 years. All participants undergo a single session of low-intensity resistance exercise involving the lower limbs, performed under 60% limb occlusion pressure. QST is performed before and immediately after the intervention, including: Pressure Pain Thresholds (PPT) measured with a digital algometer Conditioned Pain Modulation (CPM) using cold-water immersion Thermal thresholds assessed with a computer-controlled thermode Temporal summation (TS) of pain via repeated pressure stimuli The aim of this study is to explore the involvement of neurophysiological mechanisms-both central and peripheral-in the pain modulatory response following BFR exercise. This study is conducted at CUADI (Centro Universitario de Asistencia, Docencia e Investigación) in Rosario, Argentina. The results will contribute to basic science knowledge on pain physiology in healthy individuals and may inform future applied research in rehabilitation contexts. Sample size considerations: The estimated sample size is approximately 20 participants. This number is based on a preliminary power analysis conducted from pilot data on PPT changes following cold water immersion, which showed a mean difference of 0.77 kgf with a standard deviation of 0.33 kgf. Using G\*Power software (v3.1), the calculated sample size for a paired comparison with 95% power and alpha of 0.05 was 16 subjects. To account for potential data loss or dropouts, we plan to include at least 20 individuals. This sample size is considered adequate for a mechanistic, single-arm pre-post design focusing on within-subject changes in pain modulation outcomes.