Temporal summation of muscle pain evoked by very fast pressure sequences and rotation.

BACKGROUND

Pressure evoked temporal summation of pain has been described with slow repetitions (<0.5 Hz) relative to what is recommended originally for assessing temporal pain summation (>1 Hz). This study examined temporal summation of pain by repeated computer-controlled pressure stimulation at high repetition rates with and without simultaneous active probe rotations for potential better efficiency.

METHODS

In 15 healthy subjects, 15 pressure stimuli (300 and 500 ms durations) were delivered at the pressure pain threshold intensity with and without rotation of a rounded probe (1 cm(2)) at three repetition frequencies (1.5, 1, 0.5 Hz). The pressure pain intensity was continuously rated on a visual analogue scale (VAS) and scores after each stimulus were extracted and normalized to the first score.

RESULTS

The peak VAS score was larger for rotational (p < 0.001), longer stimulus duration (p < 0.02), and lower frequencies (p < 0.05) compared with non-rotational, shorter stimulus duration, and higher frequencies, respectively. VAS scores progressively increased from the first to the fifteenth stimulus (p < 0.01). The sum of VAS scores was higher after 1 Hz stimulation compared with 0.5 and 1.5 Hz stimulations (p < 0.01). Finally, the VAS sum was higher after rotational as well as longer stimulus duration compared with non-rotational and shorter stimulus duration paradigms (p < 0.01).

CONCLUSIONS

An optimum of 500 ms repeated pressure stimulation at 1 Hz produced the most apparent temporal summation of pain sensation which further was enhanced during probe rotation. These findings suggest an optimized and novel method to improve the current procedures for assessing temporal summation of pressure-induced pain.