Strong aerobic exercise is supposed to reduce pain perception. It is unclear whether aerobic exercise differentially affects noxious and non-noxious perception. The experimental project addresses possible differential effects on superficial vs. deep pain and nociceptive vs. non-nociceptive processing.

Twenty-two healthy volunteers participated in both exercise (Ex) and control (Con) conditions (23.40.9 yr, meansem; 14 f, 8 m). Due to possible influence of distraction on modulatory effects, participants were asked to cycle (20 min) and to control heart rate in both sessions. Under aerobic Ex condition, heart rate was adjusted to 75% of predicted maximum (220-age). During Con, heart rate increase was limited to 125% of individual resting pulse. Psychophysical testing was performed on the dominant hand before, 5 and 15 minutes during, and 5 and 15 minutes after cycling. Pressure pain threshold (PPT, deep pain) was assessed over the thenar and vibration detection threshold (VDT) over the processus styloideus radii. Mechanical pain (MPT, superficial pain) and detection thresholds (MDT, touch) were measured on hairy skin of hand dorsum. Subjects were asked to rate cycling exercise intensity according to the Borg CR10 scale (0 to 10).

HR controlled exercise resulted in higher Borg ratings during Ex (4.70.2) than in Con (0.60.1, p<0.001). MPT remained unchanged. MDT similarly increased in both sessions (Ex: +7966%, Con: +8735%). PPT exclusively increased in Ex by 104% (p<0.001) with significant differences to Con at 15 min during and 15 min after cycling (p<0.05). VDT decreased in both Con (-102%, p<0.001) and Ex (-283%, p<0.001). VDT changes in Ex preponderated values under Con condition during (p<0.001) and after (p<0.05) cycling.

Strong aerobic exercise as monitored by heart rate measurement and Borg scale rating inhibits deep myofascial pain (PPT). Superficial cutaneous pain (MPT) evoked by mechanical stimulation is not affected. Transient increase of PPT corroborates myofascial hypoalgesia due to Ex. Sustained reduction of VDT documents exercise induced pallhypesthesia. Comparable amount of distraction probably causes impairment of innocuous mechanical perception (MDT) in both experimental conditions. These findings indicate divergent modulations of superficial vs. deep pain and nociceptive vs. non-nociceptive processing by strong aerobic exercise.