Exercise and conditioned pain modulation have different effects on cuff pressure pain tolerance in humans

Abstract

Abstract Background/aims Exercise and experimental pain is known to cause an acute decrease of the pain sensitivity. Assessment of pain inhibitory mechanisms is often done by paradigms of exercise and experimental pain in both healthy subjects and pain patients. It is currently unknown whether pain and different types of exercise has similar effects on pain sensitivity. The aim of the present study was to investigate the effects of experimental pain and different types of exercise on deep tissue pain tolerance in healthy subjects. Methods On two separate days fifty-four healthy subjects (23 females, 33.8 ± 15.0 years) were assigned in random order to cold pressor tests (ice water at 1–2°C; 120 s duration) for the dominant hand and foot, bicycling exercises (100 W and 200 W; 20 min duration), and isometric contraction exercises (30% and 60% of maximal voluntary contraction, MVC; 180 s duration) of the dominant quadriceps and biceps brachii muscles. Before, immediately after, and 10 min after cold pressor tests and exercises, pressure pain tolerance (PTT) were assessed with computerized cuff-algometry at the non-dominant lower-leg and upper arm. Subjects reaching maximum stimulation intensity at baseline were excluded from the analysis. PTTs were analysed with repeated measures ANOVA and multiple comparisons. Results Immediately and 10 min after the cold pressor test in the dominant hand and foot significantly increased PTTs were found at the non-dominant upper arm and lower leg (P < 0.05). Both intensities of dominant biceps brachii isometric contractions produced a significant increase in the PTT at the non-dominant lower leg immediately after and 10 min after contractions (P < 0.05). After the 30% dominant quadriceps isometric contraction the PTT at the non-dominant lower leg was significantly increased (P < 0.05). Conclusion Cold pressor pain produced a contralateral and extrasegmental increase in deep tissue pain tolerance. Isometric arm exercise produced an extrasegmental increase in pain tolerance, whereas isometric leg contractions produced a contralateral effect. Aerobic exercise had no effect on pain tolerance. Thus, exercise and pain related inhibitory effects were not comparable. Acknowledgment/disclosures H.B. Madsen was supported by grants from the philanthropic foundation TrygFonden (7-11-0990), The Danish Rheumatism Association 8R95-A1871), The Research Foundation of the Danish Physiotherapy Association and The Fund for Physiotherapy in Private Practice.