Previous research has shown that in pain-free individuals, aerobic and isometric exercise can induce higher pain thresholds and pain tolerance even after a single bout.
However, in people dealing with chronic pain, the hypoalgesic response is not only lower but can sometimes have a negative effect on pain thresholds and pain tolerance.
Previous research has also shown that pre-treatment information can modulate the experience of pain, especially positive information, however it is unknown how negative information can influence exercise-induced hypoalgesia (EIH).
Primary aim of study was to investigate if individuals receiving positive pre-exercise information about the effect of an isometric wall squat exercise on pain would experience a larger EIH response compared with individuals receiving negative information. Additionally, the authors wanted to determine if the hypoalgesic response was confined just to the exercising muscle.
83 pain-free participants from a Danish university setting were randomized into three groups. They received either a 2-3 minute information session on how previous exercise had shown that exercise can reduce the experience of pain, neutral information elaborating on how to perform the wall squat exercise, or negative suggestion that previous studies have shown that exercise increases muscle pain.
All participants performed an isometric wall squat exercise for a max of 3 minutes or until fatigue. Baseline pain was taken prior to the exercise and then at 1,2, and 3 minutes.
The positive information group had a 22% increase in thigh pain-pressure threshold (PPT). The negative information group had a 4% decrease in thigh PPT. The group receiving neutral information had an increase in PPT but not as significant as the group receiving positive information.
In the non-involved trapezius muscle, the group receiving positive information had a 10% increase in PPT whereas the negative group had a 7% decrease in PPT. The neutral group again had a positive response in PPT but not as significant as the group receiving positive information.
The main finding of this study is that people receiving negative pre-exercise information experienced hyperalgesia compared with individuals receiving positive or neutral pre-exercise information.
