753: Engaging Descending Pain Inhibition Through HIIT in Pain-Free Adults: A Randomized Controlled Trial

Topic: Experimental (Non-clinical) Human Studies
Subtopic: Non -specific to any diagnosis, Pain mechanisms (e.g. descending inhibitory control, placebo, inflammation), Physiotherapy, Quantitative Sensory testing (static and dynamic, e.g., HPT, PPT, CPM, TSP, offset analgesia)

Background and Aims: Chronic pain remains a leading cause of disability worldwide, imposing substantial individual and societal burdens and underscoring the need for non-pharmacological strategies that target endogenous pain modulation¹,². Athletes consistently demonstrate higher pain thresholds and tolerance than non-athletes, an adaptation attributed to repeated high-intensity training and the phenomenon of exercise-induced hypoalgesia (EIH)³⁻⁵. Impaired conditioned pain modulation (CPM) is a hallmark of many chronic pain conditions, making interventions that engage descending inhibition particularly clinically valuable. Beyond physiological mechanisms, psychological factors, including optimism, pain catastrophizing, and perceived social marginalization, influence pain sensitivity and may affect how individuals respond to exercise-based interventions⁶⁻⁹. However, whether repeated high-intensity interval training (HIIT) affects pain sensitivity and its association with psychological factors in non-athletic populations remains poorly understood. Therefore, we examined whether HIIT sessions, single or repeated, would (1) reduce experimental pain sensitivity, (2) enhance conditioned pain modulation efficiency, and (3) alter psychological factors in pain-free, non-athletic adults.

Methods: This analysis presents interim data from an ongoing randomized controlled trial (NCT07083219). Twenty pain-free adults aged 18–50 years were randomized into two groups: a Multiple Exercise Session group (MES; n=8) completing four HIIT sessions over two weeks, and a Single Exercise Session group (SES; n=12) completing one HIIT session. Before randomization, participants underwent an individualized graded exercise test (GXT) on a cycle ergometer to determine peak power output; HIIT sessions were prescribed at 90% of peak power with sessions separated by at least 48 hours. Outcomes assessed pre- and post-intervention included quantitative sensory testing (heat pain threshold (HT), heat pain tolerance (HTO), and CPM efficiency, indexing endogenous pain inhibition) and validated psychological measures: Life Orientation Test-Revised (LOT-R), State Optimism Measure (SOM), Pain Catastrophizing Scale (PCS), and Perceived Social Marginalization Scale (PSMS). A 2 (Group) × 2 (Time) repeated-measures ANOVA evaluated main effects and interactions, with significance set at p<0.05.

Results: Repeated-measures ANOVA revealed significant main effects of time across the pooled sample, indicating exercise-induced changes in pain sensitivity and pain modulation. HTO increased significantly from pre- to post-intervention (F=5.66, p=0.022, η²=0.130), and HT also increased (F=6.56, p=0.015, η²=0.143), consistent with an exercise-induced hypoalgesic response. CPM efficiency improved significantly over time (F=4.41, p=0.042, η²=0.104), suggesting enhanced engagement of descending pain-inhibitory pathways. No significant Group × Time interactions were detected for any sensory outcome (all p>0.05), indicating that a single HIIT session produced hypoalgesic and CPM benefits comparable to four sessions. None of the psychological factors (LOT-R, SOM, PCS, PSMS) changed significantly over time, consistent with the relatively stable nature of these constructs in pain-free individuals, and no Group × Time interactions emerged; however, groups differed at baseline on state optimism (F=5.29, p=0.027) and life orientation (F=4.48, p=0.041), reflecting pre-existing group differences rather than intervention effects.

Conclusions: These interim findings from an ongoing randomized controlled trial demonstrate that high-intensity interval training acutely decreases experimental pain sensitivity and enhances endogenous pain inhibition, as indexed by improved CPM efficiency, in non-athletic adults. The absence of a significant Group × Time interaction in this interim sample suggests potential acute effects of a single HIIT bout, though the study is currently underpowered to definitively test dose-response differences. None of the psychological factors (LOT-R, SOM, PCS, PSMS) changed significantly, which may reflect that participants were healthy, pain-free individuals in whom these constructs are relatively stable, suggesting that observed sensory changes reflect physiological rather than psychological mechanisms.

Clinical Relevance: These results support HIIT as a feasible, low-cost, non-pharmacological strategy clinicians can integrate into rehabilitation to engage descending pain-inhibitory pathways, while emphasizing the need to test HIIT-based interventions in chronic musculoskeletal pain populations with impaired CPM where psychological factors may show greater modifiability.

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Presenting Author: Priyanka Rana
Submitting Author: PRIYANKA RANA

Senior Author: Alvaro Gurovich

IASP 2026 Global Year theme of Neuropathic Pain: No

• Priyanka Rana: PT, MPT, PhD - Department of Physical Therapy and Movement Science, The University of Texas at El Paso, El Paso, TX, USA
• Akash Singh: PT, MPT - Department of Physical Therapy and Movement Science, The University of Texas at El Paso, El Paso, TX, USA
• Carolina Valencia: PhD - Department of Rehabilitation Science, The University of Texas at El Paso, El Paso, TX, USA
• Alvaro Gurovich: PT, PhD, FACSM - Department of Physical Therapy and Movement Science, The University of Texas at El Paso, El Paso, TX, USA