Pain Perception and Exercise-Induced Hypoalgesia Across Circadian Rhythms

N/ANot Yet RecruitingNCT07290465

Medipol University56 enrolled

Overview

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

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.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

Interventions

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 BreathingBEHAVIORAL

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.

Eligibility

Sex: ALLMin age: 18 YearsMax age: 40 YearsHealthy volunteers:

Medical Language ↔ Plain English

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

Outcomes

Primary Outcomes

Pressure Pain Threshold (PPT)

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

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)

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

Munich Chronotype Questionnaire (MCTQ)

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.