Skip to main content
OpenTrials
Not Yet Recruiting

NCT Number: NCT07290465

Pain Perception and Exercise-Induced Hypoalgesia Across Circadian Rhythms

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

Not Yet Recruiting

Trial opening soon.

Get Notified

Key information

Conditions

Exercise Induced Hypoalgesia Agnosia Chronotype Circadian Rhythm Healthy Participants Nervous System Diseases Neurobehavioral Manifestations Neurologic Manifestations Pain Perception Pathological Conditions, Signs and Symptoms Perceptual Disorders Physical Therapy Signs and Symptoms

Age range

18 year–40 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Istanbul Medipol University

Istanbul, Beykoz, 34810, Turkey (Türkiye)

Location contact

Fatema Mohamed Soliman, PT, MSc (Cand.)

CONTACT

[email protected]

+90 537 736 20 79 ext. +20 15 0156870

About this study

Exercise-induced hypoalgesia (EIH) is a temporary reduction in pain sensitivity following physical activity. High-intensity functional training (HIFT) has been shown to produce EIH, yet the influence of circadian rhythms on this response is not well established. Circadian timing regulates physiological processes, including pain modulation, and may contribute to variability in exercise-related analgesia.

This randomized crossover trial will examine whether time of day (morning vs. evening) affects EIH in healthy adults. It will also explore the relationship between an individual's chronotype, the efficacy of EIH and the difference in magnitude between men and women, the difference in effect between bony and muscular landmarks for pressure stimulus application.

Null Hypothesis (H0) : Circadian rhythm has no significant influence on the efficacy of exercise-induced hypoalgesia (EIH), as measured by changes in pain perception before and after high intensity functional training at different times of day (morning vs. evening).

Alternative Hypothesis (H1): Circadian rhythm significantly influences the efficacy of exercise-induced hypoalgesia (EIH), with differences in pain perception before and after high intensity functional training depending on the time of day (morning vs. evening).

Each participant will complete both morning and evening sessions in randomized order, separated by ≥72 hours. Participants who completed the morning sessions will cross over to the evening sessions and vice versa. Within each session, they will perform a 12-minute supervised deep breathing control condition and a 12-minute HIFT intervention, separated by a 30-minute rest.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Healthy participants
  • age 18 to 40 years
  • good level of English that allow the enrolled participant to provide informed consent and complete the questionnaires provided
  • being categorized as "moderate" in the International Physical Activity Questionnaire (IPAQ)

Exclusion criteria

  • inability to report pain intensity reliably
  • consumption of narcotics or tobacco products
  • regularly taking pain medications and analgesics
  • pregnant or planning to get pregnant
  • surgery within the last 12 months
  • acute or chronic pain conditions
  • uncontrolled hypertension
  • cardiovascular diseases, pulmonary diseases, neurological diseases with significant changes in somatosensory and pain perception, metabolic diseases, serious systemic diseases or conditions that restrict normal daily activities, inflammatory conditions (e.g. rheumatoid arthritis), or orthopedic injuries
  • intolerable pain during the pain perception test
  • serious psychiatric conditions (e.g., schizophrenia and bipolar disorder) or psychological disorders (e.g., depression) that may affect pain thresholds (16).
  • Severe sleep disorders and circadian rhythm disturbances
  • BMI > 30
  • serious fatigue or delayed-onset muscle soreness (9) at least 24 h after exercise sessions or a sudden change in activity for more than one week

Treatment and study plan

High-Intensity Functional Training (HIFT)

Behavioral

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.

Supervised Deep Breathing

Behavioral

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.

Primary outcomes

  1. Pressure Pain Threshold (PPT)

    Time frame: Baseline (0 minute before intervention) and immediately post-intervention (within 2 minutes) Measured in both high intensity functional training (HIFT) and supervised deep-breathing conditions during each morning and evening session

    Pressure Pain Threshold (PPT) will be measured using an algometer at standardized bony and muscular landmarks. Pressure Pain Threshold (PPT) is defined as the minimal pressure at which a participant first perceives pain. Changes in Pressure Pain Threshold (PPT) will be used to assess the magnitude of exercise-induced hypoalgesia (EIH).

    Unit: kg/cm²

  2. Pressure Pain Tolerance (PPTol)

    Time frame: Baseline (0 minute before intervention) and immediately post-intervention (within 2 minutes) Measured in both high intensity functional training (HIFT) and supervised deep-breathing conditions during each morning and evening session

    Pressure Pain Tolerance (PPTol) will be measured using an algometer at standardized bony and muscular landmarks. Pressure Pain Tolerance (PPTol) is defined as the maximal pressure the participant is willing to tolerate. Changes in Pressure Pain Tolerance (PPTol) will be used to assess pain modulation in response to exercise across circadian phases.

    Unit: kg/cm²

Secondary outcomes

  1. Munich Chronotype Questionnaire (MCTQ)

    Time frame: Baseline (before any intervention session)

    Chronotype will be assessed using the Munich Chronotype Questionnaire (MCTQ). Participants will be classified as morning or evening chronotypes to examine whether individual circadian preference moderates exercise-induced hypoalgesia.

  2. Pain Catastrophizing (PCS)

    Time frame: Baseline (before any intervention session)

    Pain-related cognitions will be measured using the Pain Catastrophizing Scale (PCS) to control for potential psychological influences and understandings on pain perception. PCS is scored according to a 5-point Likert scale ranging from 0 = not at all to 4 = all the time with a maximum score of 52, with higher scores >30 indicating increased pain catastrophizing.

  3. Fear of Pain (FPQ-9)

    Time frame: Baseline (before any intervention session)

    Fear of pain will be assessed using the Fear of Pain Questionnaire-9 (FPQ-9), as psychological fear responses may influence pain reporting. Fear of Pain Questionnaire-9 (FPQ-9) is scored by using a 5-point Likert scale with a score ranging from 9 to 45 with higher scores indicate greater fear of pain.

  4. Brief Version of the Pittsburgh Sleep Quality Index (B-PSQI)

    Time frame: Baseline (before any intervention session)

    The Brief Pittsburgh Sleep Quality Index (B-PSQI) will be used to assess participants' sleep patterns and their potential influence on pain modulation. Total score ranges between 0 and 15, where higher values suggest worse quality of sleep. Scores from 0 to 5 indicate good sleep quality and scores of ≥6 poor sleep quality.

  5. Depression Anxiety Stress Scales (DASS-21)

    Time frame: Baseline (before any intervention session)

    Depression, Anxiety, and Stress Scale-21 (DASS-21) will be administered to capture psychological states that may influence experimental pain measures. Scores are presented as a total score (between 0 and 63) and a score for the three subscales (between 0 and 21). Higher scores indicate worse psychological distress.

  6. Rate of Perceived Exertion (RPE, Borg scale)

    Time frame: At minute 0 (before warm-up), at minute 5 (after warm-up), every 1 minute during the high-intensity functional training (HIFT) protocol, and at minute 17 (end of session).

    Rate of Perceived Exertion (RPE, Borg scale) will be recorded during High intensity functional training (HIFT) to confirm intensity differences between interventions. A scale of 0-10 (1 being very light, and 10 being maximum effort) is used.

  7. Rate of Perceived Relaxation (RPR)

    Time frame: At minute 0 (baseline) and at minute 12 (immediately after the supervised deep-breathing session).

    Relaxation level during supervised deep breathing control session will be assessed using a 0-10 relaxation scale. The score range is 0 (no relaxation) to 10 (maximum relaxation) with higher scores indicate better relaxation.

Study contacts

Contact information is provided by the study sponsor or research team.

Aliaa Salem Menshawi, PT, MSc (Cand.)

CONTACT

[email protected]

+905527304660 ext. +96550268508

Fatema Mohamed Soliman, PT, MSc (Cand.)

CONTACT

[email protected]

+90 537 736 20 79 ext. +20 15 0156870

Sponsors and collaborators

Lead sponsor

Medipol University

Other

Registry information

Official study title

Exploring Pain Perception Through Exercise-Induced Hypoalgesia Across Circadian Rhythms for Healthy Participants

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
Dec 18, 2025
Registry last updated
Dec 18, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

Related clinical trials

Published trials that share one or more normalized conditions with this study.