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.
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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
Enrollment
35
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
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
Pain Center, University Hospital Odense
Odense, Funen, Denmark
Pressure pain threshold at the right quadriceps muscle where injection is performed.
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.
Time frame: Before and after the 3 minutes wall squat
Pressure pain threshold at the non-dominant trapezius muscle
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.
Time frame: Before and after the 3 minutes wall squat
Pressure pain threshold at the left quadriceps muscle where injection is not performed.
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.
Time frame: Before and after the 3 minutes wall squat
Pain Intensity in thighs
Pain intensity in both thighs are assessed with numerical rating scales with 0 = no pain and 10 = maximal pain.
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
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