# Effects of 4‐Week Treadmill Running at Different Intensities on Exercise‐Induced Hypoalgesia and Endogenous Pain Modulation in Healthy Individuals

## TL;DR

This study found that 4 weeks of low-to-moderate intensity treadmill running improves pain modulation and hypoalgesia in healthy individuals.

## Contribution

The study demonstrates that low-to-moderate intensity treadmill running enhances endogenous pain modulation and exercise-induced hypoalgesia.

## Key findings

- Low-to-moderate intensity treadmill running significantly increased conditioned pain modulation (CPM).
- High intensity treadmill running showed lower hypoalgesia compared to moderate and low intensity groups.
- Acute hypoalgesia was positively correlated with CPM and negatively correlated with temporal summation.

## Abstract

We aimed to investigate changes in pain perception, acute exercise‐induced hypoalgesia (EIH), and endogenous pain modulation responses following 4‐week treadmill running exercises of different intensities in healthy individuals.

Fifty‐six healthy individuals were included in this study. All participants were randomly assigned to a control group and three experimental groups (treadmill running at high intensity [TRH], treadmill running at moderate intensity [TRM], and treadmill running at low intensity [TRL]). All participants performed 12 treadmill running sessions within 4 weeks at different intensities based on their target heart rate (THR). A running assessment was administered 1 week before running sessions. The magnitudes of EIH, conditioned pain modulation (CPM), and temporal summation (TS) responses following regular treadmill running were assessed. Pressure pain thresholds (PPTs) or mechanical pain thresholds (MPTs) were also determined following regular treadmill running.

All groups exhibited an EIH effect (p < 0.001, F = 9.424) with an increase in PPT and MPT during the running sessions (p = 0.004 and F = 2.084), and the TRM and TRL groups were significantly higher than the TRH group (p < 0.001). The CPM of the TRM and TRL groups significantly increased (p < 0.001), and the TS of the TRM significantly decreased (p < 0.001). Correlation analysis showed that the acute EIH‐A (r = 0.724, p < 0.001), EIH‐L (r = 0.726, p < 0.001), and EIH‐M (r = 0.347, p = 0.009) were positively correlated with the CPM, while EIH‐A (r = −0.529, p < 0.001) and EIH‐L (r = −0.544, p < 0.001) were negatively correlated with the TS.

A 4‐week low‐to‐moderate intensity treadmill running improved acute EIH response by enhancing endogenous pain modulation in healthy individuals. Future studies should consider sex, behavior, and physiological factors to provide a comprehensive understanding of the changes in EIH following regular exercises.

ClinicalTrials.gov identifier: ChiCTR2300074367