Reduction of experimental muscle pain by passive physiological movements

The analgesic effects of passive movements on deep-tissue pain have not been sufficiently explored in human studies. The purpose of this study was to examine the effect of passive physiological movements (PPMs) on deep-tissue pain sensitivity. Seventeen healthy subjects were included in this randomised crossover study. In one session an electrically driven bicycle performed 30 min PPM of the knee joint. Another session without PPM served as control. The effect of PPM on experimental muscle pain was assessed. Muscle pain was induced by i.m. injection of hypertonic saline into the tibialis anterior muscle and the pain intensity was scored on an electronic visual analogue scale (VAS). The pressure pain sensitivity was assessed by recording of pressure pain thresholds (PPTs). McGill Pain Questionnaire (MPQ) was used to describe the quality of the induced pain. Compared with the control session PPM demonstrated: (1) a reduction of the experimental muscle pain intensity (VAS area and peak) and duration (17–31%, P < 0.03), (2) lower MPQ score and a change in quality profile of experimental muscle pain (25%, P < 0.01) and (3) an increased PPT (17%, P < 0.0005). The present study demonstrated that PPM produced an immediate analgesic effect on deep-tissue pain indicating a possible involvement of neural inhibitory mechanisms.