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 1x3 min seated isometric knee extension exercise in healthy women. The study is a blinded 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 pressure pain thresholds (PPT) 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
DOUBLE
Enrollment
34
A bolus injection (1 ml) of hypertonic saline (5.8%) is injected into the dominant vastus medialis muscle 20 cm proximal from the basis of patella before performance of the 1x3 min Seated Isometric Knee Extension.
A bolus injection (1 ml) of isotonic saline (0.9%) is injected into the dominant vastus medialis muscle 20 cm proximal from the basis of patella before performance of the 1x3 min Seated Isometric Knee Extension
Dept. Of Health Science and Technology, Aalborg University
Aalborg, Denmark
Change in pressure pain threshold will be assessed over the dominant quadriceps muscle
Between group comparison of the primary outcome, which is change in pressure pain threshold over the dominant quadriceps muscle before and after performing seated isometric knee extension. Pressure pain threshold is measured with a handheld pressure algometer.
Time frame: Baseline, Day 2 (within 1 week of baseline), Day 3 (within 1 week of Day 2)
Pressure pain threshold at the non-dominant quadriceps muscle and non-dominant trapezius muscle
Between group comparison of the secondary outcome, which is change in pressure pain threshold at the non-dominant quadriceps muscle and non-dominant trapezius muscle from before Seated Isometric Knee Extension to after Seated Isometric Knee Extension. Pressure pain threshold is measured with a handheld pressure algometer.
Time frame: Baseline, Day 2 (within 1 week of baseline), Day 3 (within 1 week of Day 2)
Pain Intensity in dominant thigh
Pain intensity is 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 1, 2 and 3 minutes into the Seated Isometric Knee Extension, and immediately after the end of the seated isometric knee extension
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