Objective: The aim of the present analysis was to examine physiological adaptation to a sub-maximal test by measuring heart rate (HR) and heart rate variability (HRV) from the perspective of the fibromyalgia (FM) pain experience.
Method: Twenty-five women presenting FM and healthy women were education- and age-matched. In their homes, all women completed questionnaires regarding health related quality of life and physical activity. All the women performed a stepwise load increment submaximal exercise test on a cycle ergometer to the severe perceived exertion level. HR and HRV were recorded before, during and after the test. Current pain was recorded before and after the test upon the FM women.
Result: Correlational analysis over all the pain ratings and adaptation measures of HR and HRV showed that higher HR on two or three levels of workload were linked to greater clinical pain in women presenting FM. Pain at baseline related to clinical everyday pain. Both these pain measures correlated with the intersection between HR and workload and pain after the test. Reactivity through increase in pain from the test did not relate to everyday pain or baseline pain. Pain reactivity instead related to more adaptive HRV from the test, similar to the HRV adaptation of healthy women. In FM, the pain measures were neither related to HR at baseline, maximal workload during the test nor to physical exertion during the test.
Conclusion: FM implies everyday clinical pain that is related to the intersection between HR and workload. In contrast to clinical pain, pain reactivity from the test related to a more physiologically adaptive pattern in terms of HRV. Clinical pain and pain reactivity seem to mobilize separate physiological processes via separate mechanisms.