Endogenous Modulation of Pain and Stretch Tolerance

Study Overview
=================
Brief Summary
-----------------
This study investigates the role of two endogenous inhibitory mechanisms; exercise-induced hypoalgesia (EIH) and a conditioning painful stimulus (CPM) on passive joint range of motion, passive resistive torque and pain sensitivity. The study is a randomized, repeated-measures cross-over study.

Detailed Description
-----------------
The increase in range of motion following stretching is related to changes in the tolerance to stretch. The mechanistic relationships behind these changes in subject sensation are however unknown but could be related to endogenous modulation of pain.

Official Title
-----------------
Endogenous Modulation of Pain - the Tolerance to Stretch

Conditions
-----------------
Pain Threshold

Intervention / Treatment
-----------------
* Other: Exercise induced hypoalgesia (EIH)
* Other: Static stretch (SS)
* Other: Rest
* Other: Conditioned pain modulation (CPM)


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Eligibility for participation included the absence of any pain or other conditions that might affect the somatosensory system. Exclusion Criteria: Substance abuse, History of neurological or mental disabilities, Lack of ability to comply with instructions, Delayed onset of muscle soreness.

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
-----------------
Male

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: This was a randomized, repeated-measures cross-over study. Passive knee extension range of motion was measured three consecutive times with five-minute intervals between measurements. Both groups underwent a static stretch protocol consisting of two bouts of thirty-second constant-angle static stretching of the knee flexors with a one-minute rest between bouts. Subjects were instructed to keep the limb relaxed as the lower leg was passively moved towards extension. Following stretching, the post-stretch measurement was performed. Finally, subjects in the pain group were instructed to immerse their non-dominant hand into a container with circulating water at 1˚C to 4˚C and keep it there for 2 minutes. A Biodex system 4 pro dynamometer was used to quantify range of motion and passive resistive torque. Pressure pain thresholds was assessed using a handheld pressure algometer (Somedic AB, Hörby, Sweden).
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Exercise-induced hypoalgesia (EIH)<br>Exercise-induced hypoalgesia - isometric muscle contractions of the hand flexors | Other: Exercise induced hypoalgesia (EIH)<br>* An EIH response was induced by a 3-minute isometric contraction of the hand flexor muscles at 25% of maximal voluntary contraction (MVC).<br>|
| Active Comparator: Static stretch (SS)<br>A static stretch of the knee flexors | Other: Static stretch (SS)<br>* Two bouts of 30 seconds of static stretching (SS) of the knee flexors.<br>|
| Sham Comparator: Rest<br>No intervention | Other: Rest<br>* The participants rested in a seated position for 10 minutes<br>|
| Experimental: Conditioning painful stimulus (CPM)<br>Conditioned pain modulation - cold pressure test | Other: Conditioned pain modulation (CPM)<br>* A CPM response was induced by way of the cold pressor test.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Knee extension range of motion | Passively induced knee extension range of motion was measured using the Biodex system 4 pro isokinetic dynamometer | Passive knee extension range of motion was measured as a baseline just prior to the induction of exercise-induced hypoalgesia (EIH), Static stretch (SS), Rest and a conditioning painful stimulus (CPM) | 
| Knee extension range of motion | Passively induced knee extension range of motion was measured using the Biodex system 4 pro isokinetic dynamometer | Passive knee extension range of motion was measured 30 seconds after the induction of EIH, SS, Rest and CPM | 
| Knee extension range of motion | Passively induced knee extension range of motion was measured using the Biodex system 4 pro isokinetic dynamometer | Passive knee extension range of motion was measured 10 minutes after the induction of EIH, SS, Rest and CPM | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Passive resistive torque | Passive resistive torque during the passive knee extension motion was measured using the Biodex system 4 pro isokinetic dynamometer. | Passive resistive torque was measured as a baseline just prior to the induction of EIH, SS, Rest and CPM | 
| Passive resistive torque | Passive resistive torque during the passive knee extension motion was measured using the Biodex system 4 pro isokinetic dynamometer. | Passive resistive torque was measured 30 seconds after the induction of EIH, SS, Rest and CPM | 
| Passive resistive torque | Passive resistive torque during the passive knee extension motion was measured using the Biodex system 4 pro isokinetic dynamometer. | Passive resistive torque was measured 10 minutes after the induction of EIH, SS, Rest and CPM | 
| Pressure pain thresholds | Pressure pain thresholds was measures using a handheld pressure algometer (Somedic AB, Hörby, Sweden. | Pressure pain thresholds were measured as a baseline just prior to the induction of EIH, SS, Rest and CPM | 
| Pressure pain thresholds | Pressure pain thresholds was measures using a handheld pressure algometer (Somedic AB, Hörby, Sweden. | Pressure pain thresholds were measured 30 seconds after the induction of EIH, SS, Rest and CPM | 
| Pressure pain thresholds | PRessure pain thresholds was measures using a handheld pressure algometer (Somedic AB, Hörby, Sweden. | Pressure pain thresholds were measured 10 minutes after the induction of EIH, SS, Rest and CPM | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Stretch tolerance, Stretching Exercises, Exercise induced hypoalgesia