Study of the mechanisms of action of the hypoalgesic effect of pressure under shock waves application: A randomised controlled trial

Abstract

ObjectiveTo determine if the perceived pain intensity during the application of shock waves (SWs) is a determinant mechanism in producing hypoalgesic changes in pressure pain thresholds (PPTs) in asymptomatic individuals. DesignA randomised, single-blind controlled trial [NCT03455933]. SettingUniversity. ParticipantsSixty-three asymptomatic individuals. InterventionsParticipants were randomised into three groups: 1-SWs causing mild pain (SW-DP); 2-SWs generating moderate pain (SW-MP); and 3-cold pressor test (CPT). Main outcome measurementsBefore and after the intervention, the PPT was evaluated bilaterally at the following points: lateral epicondyle, median nerve in the flexure of the elbow, and tibia. ResultsThe results showed differences between various groups over time for all PPTs assessments, due to the existence of statistically significant differences in the interaction group x times (dominant arm lateral epicondyle [P < 0.001; η2p = 0.255]; dominant arm median nerve [P = 0.001; η2p = 0.212]; nondominant arm lateral epicondyle [P < 0.001; η2p = 0.275]; nondominant arm median nerve [P < 0.001; η2p = 0.268]; tibia [P = 0.012, η2p = 0.138]). The SW-MP group obtained a significant increase in all the PPT evaluations compared with the SW-DP group (d > 0.80). The CPT group only showed significantly higher results, and of high magnitude (d > 0.80), regarding the SW-DP group for the PPT evaluation in the dominant member. The SW-MP group showed differences compared with the CPT only for the PPT obtained in the nondominant arm. ConclusionsThe findings show that SW treatment generates a hypoalgesic effect on the application point, with moderate pain. Further studies are necessary in order to link these hypoalgesic changes to the activation of the descending inhibitory systems.