Evaluation of offset analgesia in deep muscle pain
Translated title
Evaluering af offset analgesia i dyb muskelsmerte
Authors
Brøndum, Pernille ; Holt, Michael
Term
4. term
Publication year
2014
Submitted on
2014-06-03
Abstract
Offset-analgesi er et fænomen, hvor en meget lille sænkning af en smertefuld stimulering giver en uforholdsmæssigt stor reduktion i oplevet smerte. Det er primært undersøgt ved smertefuld varme. Dette studie undersøgte, om samme effekt også findes ved dyb muskelsmerte. Sytten raske deltagere deltog. En standard protokol for offset-analgesi med varme blev brugt som kontrol. Vi målte også tidsmæssig summering (gradvis opbygning af smerte over tid) og betinget smertehæmning (kroppens smerte-hæmmer-smerte system) for at sikre, at deltagernes smerteregulering fungerede som forventet. Dyb muskelsmerte blev fremkaldt med en turniketmanchet ved fire smertefulde trykforhold. Offset-analgesi blev defineret som den laveste smertevurdering efter en lille sænkning i stimulusintensitet sammenlignet med en tidsmatchet vurdering under en konstant smertefuld stimulering. Resultaterne viste tydelig offset-analgesi ved varme (P < 0,001). Tidsmæssig summering og betinget smertehæmning lå inden for forventede niveauer. Derimod blev der ikke observeret offset-analgesi ved trykstimuli (P = 0,750). Inden for studiets begrænsninger understøtter resultaterne ikke, at offset-analgesi er en endogen smertelindrende mekanisme ved dyb muskelsmerte fremkaldt af smertefuldt tryk.
Offset analgesia is a phenomenon where a very small drop in a painful stimulus leads to a disproportionately large drop in reported pain. It has mostly been studied with noxious heat. This study asked whether the same effect also occurs in deep muscle pain. Seventeen healthy volunteers took part. A standard heat offset analgesia protocol was used as a control. We also measured temporal summation (the build-up of pain over time) and conditioned pain modulation (the body's pain-inhibits-pain system) to check that participants' pain modulation worked as expected. Deep muscle pain was produced by a tourniquet cuff using four noxious pressure conditions. Offset analgesia was defined as the minimum pain rating after a small decrease in stimulus intensity, compared with time-matched pain during a constant noxious stimulus. Results showed clear offset analgesia with heat (P < 0.001). Temporal summation and conditioned pain modulation were within expected ranges. In contrast, no offset analgesia was observed with the pressure stimuli (P = 0.750). Within the limits of this study, these findings do not support offset analgesia as an endogenous pain-relief mechanism in deep muscle pain evoked by noxious pressure.
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