The Effects of Intensity on Exercise-Induced Hypoalgesia During a Knee Extension Exercise
Phase: NA
Conditions: Healthy
Sponsor: University of Central Florida

The Effects of Intensity on Exercise-Induced Hypoalgesia During a Knee Extension Exercise 
NCT05561582 
5/31/2024 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

STUDY PROTOCOL 
This study was a randomized controlled trial of healthy participants.  After providing written informed 
consent, participants were screened for eligibility criteria.  Eligible participants then underwent 
Quantitative Sensory Testing procedures that included Heat Pain Threshold (HPT), Temporal Summation 
(TS), Pressure Pain Threshold (PPT), and Conditioned Pain Modulation (CPM).   
During HPT, participants were provided a thermode attached to a TCS-II (QST.Lab, Strasbourg, 
France).  The thermode increased from a baseline of 32 degrees Celsius at 1 degree C/second to a 
maximum of 50 degrees Celsius.  Participants were instructed to indicate when the sensation first 
changed from warmth to pain (pain threshold) by pressing a button.  Once the button was pressed, the 
temperature stopped increasing and quickly returned to a baseline temperature of 32 degrees 
Celsius.  Two trials were completed at the dominant quadriceps and ipsilateral upper trapezius. 
During TS, participants placed the thermode on the palmar surface of the hand.  Participants rated the 
pain intensity during a train of 10 heat pulses that were delivered to the skin with temperatures peaking 
at 49oC at a rate to maintain the desired inter-stimulus interval.   
For PPT, a computerized pressure algometer (AlgoMed, Ramat Yishai, Israel) with a 1 cm diameter 
rubber tip was applied at a constant rate.  Participants were instructed to press a response button 
connected to the algometer when the sensation first changed from pressure to pain (pain threshold).  Two 
trials were performed at the dominant quadriceps and ipsilateral upper trapezius. 
For CPM, PPT was applied to the web space of the non-dominant foot.  Participants then immersed the 
dominant hand into water cooled by a refrigeration unit (ARCTIC Series Refrigerated Bath Circulator, 
ThermoFisher Scientific, Massachusetts, USA) that circulated water continuously to maintain a constant 
temperature of 12o Celsius for 60 seconds.  PPT measurement was then repeated. 
After Quantitative Sensory Testing, participants completed a 1-repetition maximum test for a leg 
extension exercise with the dominant lower extremity.   
Participants were then randomly assigned to either the high intensity exercise, low intensity exercise, or 
quiet rest intervention.  For participants assigned to the exercise interventions, individuals completed a 
single leg knee extension exercise for 3 sets, 10 repetitions on the dominant leg.  A weight corresponding 
to either 30% or 75% of the participants 1-repetition maximum was added for the low intensity or high 
intensity group, respectively.  For individuals assigned to the quiet rest intervention, participants sat 
quietly for two minutes three sets.  Between each set or exercise or quiet rest, PPT was measured on 
the dominant quadriceps and upper trapezius.   
After exercise, CPM was repeated. 
STATISTICAL ANALYSIS 
To examine the immediate changes in PPT by group, a mixed model ANOVA was conducted.  Simple 
effects decomposition with Bonferroni correction were completed.  Our a priori alpha level is <0.05.   
A Pearson correlation examined for the association of HPT, TS, baseline PPT with Exercise-Induced 
Hypoalgesia.  
To examine if CPM efficiency changes by group, a mixed model ANOVA was conducted.