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NCT Number: NCT04354948

Influence of Pain on Exercise-induced Hypoalgesia

The purpose of this study is to investigate how acute pain induced by hypertonic saline prior to exercise influence the magnitude of exercise-induced hypoalgesia after a 3 min isometric wallsquat exercise in healthy subjects. The study is a single blinded (investigator) randomized cross-over trial The results from the study may be of great importance to the understanding of exercise-induced hypoalgesia, and whether the presence of pain affects the effects of exercise.

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Key information

Conditions

Pain Neurologic Manifestations Pathological Conditions, Signs and Symptoms Signs and Symptoms

Age range

18 year–50 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Pain Center, University Hospital Odense

Odense, Funen, 5000, Denmark

About this study

Exercise is recommended to promote and maintain health and as treatment for more than 25 chronic diseases and pain conditions.

The mechanisms underlying pain relief of exercise are largely unknown but may be related to the modulation of central descending pain inhibitory pathways after acute exercise bouts. Exercise-induced hypoalgesia (EIH) is typically assessed as the temporary change in PPTs after a short acute exercise bout and EIH is seen as a proxy of descending pain inhibitory control. In general, EIH seems hypoalgesic (functional) in asymptomatic subjects. A hyperalgesic (impaired) EIH response has been reported in different chronic pain populations, although a functional EIH response also has been reported in subgroups of knee osteoarthritis patients. This implies differences in the acute response to exercise between healthy (pain-free) subjects and chronic pain patients, but it is still unknown whether the presence of pain itself affects the pain alleviating response (i.e. the EIH response) to acute exercise.

It is hypothesized that acute pain will decrease the EIH response magnitude following hypertonic saline injection compared with the control injection. This study will increase the insight into the EIH mechanisms in healthy subjects in general, and how the presence of pain affects the body's own ability to modulate pain during exercise.

Who can participate

Healthy volunteers accepted: Yes

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

Inclusion criteria

  • Pain-free
  • Understands and writes Danish

Exclusion criteria

  • Pregnancy
  • Previous addictive behavior defined as abuse of hash, opioids or other euphoric substances.
  • Previous painful or mental illnesses, neurological or circulatory diseases in the form of heart or lung disease.
  • Surgery within last 3 months
  • Pain on the days of testing
  • Pain for more than 2 weeks within the last 3 months

Treatment and study plan

Pain (hypertonic saline)

Behavioral

A bolus injection (1 ml) of hypertonic saline (5.8%) is injected into the right quadriceps femoris of the quadriceps femoris muscle 1 minute before performance of the 3 min wall squat exercise

No pain (Hypotonic saline)

Behavioral

A bolus injection (1 ml) of isotonic saline (0.9%) is injected into the right quadriceps femoris of the quadriceps femoris muscle 1 minute before performance of the 3 min wall squat exercise

Primary outcomes

  1. Pressure pain threshold at the right quadriceps muscle where injection is performed.

    Time frame: Before and after the 3 minutes wall squat

    Between group comparison of the primary outcome, which is change in pressure pain threshold at the right quadriceps muscle from before wall squat to after wall squat. Pressure pain threshold is measured with a hand held pressure algometer.

Secondary outcomes

  1. Pressure pain threshold at the non-dominant trapezius muscle

    Time frame: Before and after the 3 minutes wall squat

    Between group comparison of the secondary outcome, which is change in pressure pain threshold at the left trapezius muscle from before wall squat to after wall squat. Pressure pain threshold is measured with a hand held pressure algometer.

  2. Pressure pain threshold at the left quadriceps muscle where injection is not performed.

    Time frame: Before and after the 3 minutes wall squat

    Between group comparison of the secondary outcome, which is change in pressure pain threshold at the left quadriceps muscle from before wall squat to after wall squat. Pressure pain threshold is measured with a hand held pressure algometer.

  3. Pain Intensity in thighs

    Time frame: Assessed before and immediately after hypertonic and isotonic saline injection as well as after 1, 2 and 3 min of wall squat, and immediately after the end of wall squat

    Pain intensity in both thighs are assessed with numerical rating scales with 0 = no pain and 10 = maximal pain.

Other outcomes

  1. Pressure pain threshold

    Time frame: At baseline on both days before saline injections

    Cuff pressure pain threshold (cPPT) is assessed using a computer-controlled cuff pressure algometer (CPAR, NociTech, Denmark,). A 13-cm wide silicone tourniquet cuff is wrapped around the right lower leg with an 8-cm distance to the tibial tuberosity. The cuff pressure is increased with a rate of 1 kPa/s and the maximal pressure limit is 100 kPa. The participants use an electronic visual analog scale (VAS) to rate the pressure-induced pain intensity and a button to release the pressure. Zero- and 10-cm extremes on the VAS were defined as "no pain" and as "maximal pain," respectively. The participants are instructed to rate the pain intensity continuously on the electronic VAS from when the pressure was defined as first sensation of pain and to press the pressure release button when the pain was intolerable. The pressure value when the subject rated the sensation of pain as 1 cm on the VAS was defined as the cPPT.

  2. Pressure pain tolerance

    Time frame: At baseline on both days before saline injections

    Cuff pressure pain tolerance (cPTT) is assessed using a computer-controlled cuff pressure algometer (CPAR, NociTech, Denmark,). A 13-cm wide silicone tourniquet cuff is wrapped around the right lower leg with an 8-cm distance to the tibial tuberosity. The cuff pressure is increased with a rate of 1 kPa/s and the maximal pressure limit is 100 kPa. The participants use an electronic visual analog scale (VAS) to rate the pressure-induced pain intensity and a button to release the pressure. Zero- and 10-cm extremes on the VAS were defined as "no pain" and as "maximal pain," respectively. The participants are instructed to rate the pain intensity continuously on the electronic VAS from when the pressure was defined as first sensation of pain and to press the pressure release button when the pain was intolerable. The pressure value when the subject terminates the pressure inflation is defined as the cPTT.

  3. Temporal summation of pain

    Time frame: At baseline on both days before saline injections

    Temporal summation of pain (TSP) is assessed at the right lower leg with computer-controlled cuff algometry. Ten repeated cuff pressure stimulations lasting 1 second each (1 sec breaks in between) are induced to assess TSP. Stimulations are delivered by rapid inflation of the cuff with an intensity equivalent to the pressure pain tolerance. Subjects rate the pain intensity on an electronic VAS continuously during the sequential stimulation without returning the VAS to zero between stimulations. VAS scores immediately after each stimulus are extracted, and TSP is calculated as the ratio of the last 3 stimulations to the first four stimulations, with positive values indicating an increase in pain intensity ratings during the repeated stimulation.

  4. International Physical Activity Questionnaire (IPAQ)

    Time frame: Baseline of first session

    The IPAQ is suitable for adults between 15 and 69 years of age and is used for sample surveillance of physical activity levels.

Sponsors and collaborators

Lead sponsor

Odense University Hospital

Other

Collaborators

  • Aalborg University

Registry information

Official study title

The Influence of Pain on Exercise-Induced Hypoalgesia in Healthy Subjects: A Randomized Controlled Trial

Important dates

Study start
2020
Primary completion
2020
Study completion
2020
First posted
Apr 21, 2020
Registry last updated
Sep 22, 2020

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.

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