Introduction: Exercise-induced hypoalgesia is a phenomenon in which exercise bouts induce a reduction in pain sensitivity. Apnea training involves similar characteristics that could potentially induce hypoalgesia. Objectives: The objectives of this study are to explore the effect of apnea training on hypoalgesia; assess the correlation between conditioned pain modulation (CPM) response and apnea-induced hypoalgesia; and examine the association between hypoalgesia with hypoxemia, and heart rate (HR) during apnea. Methods: A randomized controlled trial was conducted comparing a walking protocol employing intermittent apnea compared with normal breathing in healthy volunteers. Hypoalgesia was tested with pressure pain thresholds (PPTs) and CPM. Oxygen saturation (SpO₂) and HR were also tested. Results: Relevant but not significant changes were detected in the thumb (MD = 0.678 kg/cm²), and tibialis (MD = 0.718 kg/cm²) in favor of the apnea group. No significant differences were detected in CPM. The apnea group presented lower SpO₂, but HR values similar to those of the control group during the intervention. Basal CPM and intrasession hypoxemia significantly correlated with the PPT response. However, HR did not correlate with the PPT response. Conclusions: The current results suggest a trend, though not statistically significant, toward an improvement in the PPT in favor of apnea training compared to normal breathing. Nevertheless, subjects who presented greater basal CPM and lower oxygen saturation during the session presented a greater PPT response, suggesting the possibility of mediators of response. Future investigations should clarify this phenomenon.

Intermittent apnoeas may induce hypoalgesia; however, the effects of low‐lung‐volume static apnoea have not been investigated. Eighty healthy participants were randomized to an apnoea group (AG) or a control group (CG). The AG performed a 6‐min protocol of intermittent static apnoea at low lung volume (passive exhalation), whereas the CG breathed normally in the supine position. Pressure pain thresholds (PPTs) were assessed at the thumb, tibialis anterior and C7, together with heart rate (HR), oxygen saturation (), and systolic and diastolic blood pressure (SBP and DBP). Open‐ended questions explored sensations, emotions and adverse effects. ANCOVA (baseline pressure pain threshold) revealed no significant between‐group differences in PPT at thumb (mean difference [MD] = −0.209 kg/cm ² ; 95% CI: −0.584, 0.158; P = 0.268), tibialis (MD = 0.014 kg/cm ² ; 95% CI: −0.341, 0.354; P = 0.939), or C7 (MD = −0.276 kg/cm ² ; 95% CI: −0.669, 0.102; P = 0.169). Intrasession analyses showed higher values in the AG for (MD = 0.598%, P = 0.009), percentage maximum heart rate (MD = 4.344%, P < 0.0001), SBP (MD = 15.344 mmHg, P < 0.0001) and DBP (MD = 14.273 mmHg, P < 0.0001). The AG reported more distress‐related sensations and emotions, whereas the CG described more comfort‐related experiences. Adverse effects were mild. A 6‐min intermittent low‐lung‐volume static apnoea did not induce hypoalgesia despite autonomic and cardiovascular activation and was well tolerated. These findings suggest respiratory‐induced autonomic stress may be insufficient to modulate nociceptive processing, highlighting the importance of physiological conditions under which breath‐hold interventions may influence pain. Trial registration: This study was prospectively registered on 27 November 2023, at ClinicalTrials.gov (Identifier: NCT06158256).

Cristian Mendoza-Arranz, Guillermo Miravet-Mingo, José Fierro-Marrero, Álvaro Reina-Varona, Jose Vicente León-Hernández, Asier Sagarribay-Villano, Hugo García-del Arco, and Francisco De Asís-Fernández. Korean J Pain -0001;0:. https://doi.org/10.3344/kjp.25130