Pain Perception and Exercise-Induced Hypoalgesia Across Circadian Rhythms

Summary

The goal of this randomized crossover clinical trial is to investigate whether exercise-induced hypoalgesia (EIH) is influenced by circadian rhythm in healthy adults aged 18-40 years.

The main questions it aims to answer are:

* Does the time of day (morning vs. evening) influence changes in pain perception following exercise?
* Do chronotype, sex, or stimulation site (bony vs. muscular) alter the magnitude of this effect?

Participants will:

* Complete questionnaires
* Undergo quantitative sensory testing
* Attend both morning and evening sessions in randomized crossover order

Conditions

• Exercise Induced Hypoalgesia
• Circadian Rhythm
• Pain Perception
• Healthy Participants
• Chronotype
• Physical Therapy

Interventions

BEHAVIORAL

High-Intensity Functional Training (HIFT)

A 12-minute, instructor-led HIFT protocol delivered via the same video to all participants. After a 5-minute warm-up, participants perform six exercises targeting major muscle groups. The exercises are 4 lunges followed by one push-up, 10 high knees followed by 10 shuffles, burpees, squat jumps, skaters, and plank up-downs. Each exercise is done for 40 seconds then 20 seconds rest. The cycle repeats twice for a total of 12 minutes. Rate of Perceived Exertion (Borg scale) is recorded at baseline, post-warmup, during each rest interval, and immediately post-exercise. A physiotherapist supervises performance, ensures correct technique, and enforces safety and target intensity while motivating and encouraging the participant.

BEHAVIORAL

Supervised Deep Breathing

A 12-minute deep breathing session delivered via a prerecorded audio and supervised by a physiotherapist. The breathing rhythm includes inhaling for 4 seconds and exhaling for 6 seconds for a total 1 minute, followed by 1 minute of normal breathing. This cycle is repeated six times for a total duration of 12 minutes. Participants lie supine in a comfortable position and wear headphones. A self-reported Rate of Perceived Relaxation (RPR, 0-10) is recorded before and after. This serves as a non-exercise control to account for relaxation and attention effects.

Sponsors & Collaborators

• Medipol University

  lead OTHER

Principal Investigators

• Gizem Ergezen Şahin, Dr. Assistant Professor · Department of Physiotherapy and Rehabilitation/Istanbul Medipol University

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

DOUBLE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

40 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2026-01-31

Primary Completion

2026-03-31

Completion

2026-04-30

Countries

• Turkey (Türkiye)

Study Locations