The effects of static muscular contraction on blood pressure, heart rate, pain ratings and pressure pain thresholds in healthy individuals and patients with fibromyalgia.

Aberrations of cardiovascular regulation and dysfunction of endogenous pain modulation have been reported in fibromyalgia (FM) patients. This study aimed at investigating the interactions between cardiovascular regulation and pain perception during static muscle contractions. Seventeen FM patients and 17 healthy controls performed a standardised static contraction (m. quadriceps femoris dx) until exhaustion. Blood pressure (BP), heart rate (HR), ratings of exertion/fatigue and pain intensity as well as pressure pain thresholds (PPTs) (at m. quadriceps dx and m. deltoideus dx) were assessed before, during and 15 min following contraction. Systolic and diastolic BP increased during contraction (p<0.001) and decreased following contraction (p<0.001) in both groups alike. A significant increase in HR was seen during contraction in FM patients (p<0.001), but not in healthy controls (difference between groups p<0.02). The rated exertion/fatigue and pain intensity increased more during contraction and remained elevated longer following contraction in the patient group. PPTs were lower in patients compared to controls at both sites at all times (p<0.001). No group differences in PPT changes over time were found. In conclusion, no indication of an attenuated cardiovascular response to exercise was found in our FM patients. The more pronounced HR increase in patients during contraction was most likely due to deconditioning. No exercise related change in PPTs was seen in either group, most likely due to insufficient exercise intensity, but the contraction induced pain was more pronounced in the FM patients.