(203) - Within session reliability of conditioned pain modulation in young healthy adults depends on location of test stimulus

Abstract

The aim of this repeatability study was to investigate the between and within session reliability of conditioned pain modulation (CPM) in young healthy individuals. Thirty subjects (19.3 ± 1.5 years; 15 females) participated in two randomized sessions separated by approximately one week. During each session, pressure pain thresholds (PPTs) at the right quadriceps and upper trapezius muscles were assessed before and during ice water immersion (left foot, 0 ± 1°C, 105 ± 18 seconds). In one of the sessions, the CPM protocol was repeated following 23 minute quiet rest. Percentage change in CPM within and between sessions at each assessment site were compared with repeated measures ANOVAs. Intraclass correlations (ICCs (3,k)) with 95% confidence interval (CI) as a measure of relative reliability were computed within and between sessions for each assessment site. During submersion of foot in the ice water bath, participants reported moderate-to-severe peak pain intensity (6.6 ± 1.8 using 0/10 Numerical Rating Scale). Peak pain intensity decreased significantly between sessions (7.0 ± 1.0 to 6.4 ± 1.7; P = .01) but was similar within session (P > .05). PPTs significantly increased during cold pressor tests compared to baseline without ice (P < .001). The CPM response decreased at the quadriceps and upper trapezius muscles similarly following quiet rest compared with before quiet rest (trial: P < .05; trial x site: P > .05). Despite the decrease, CPM had a fair-to-good within session reliability; although this differed based on the location of the test stimulus (ICCs: quadriceps = .707 [.395–.859]; upper trapezius = .433 [−.190–.730]). Between-session reliability was poor at both assessment sites (ICCs: quadriceps = .208 [−.715–.628]; upper trapezius = .350 [−.401–.694]). These results suggest that CPM is not fully restored following a 23-minute washout period and reliability of CPM may change depending on location of the test stimulus. Future studies are needed to investigate the factors involved in CPM reliability.