Perception of pain and exertion during exercise on a cycle ergometer in chronic pain patients

HYPOTHESIS: Chronic pain patients (CPP) are generally thought to present with reduced fitness in relation with pain enhancement during exercise. A distortion of exertion perception may coexist, which could lead CPP to reduce physical activities. DESIGN: Case-control study, with a nonrandomized consecutive sample that was age matched. SETTING: A Chronic Pain Unit in a Multidisciplinary Pain Center of a university hospital in a city of > 1,000,000 inhabitants. SUBJECTS: 42 CPP referred for evaluation and 34 controls (staff members and relatives). OUTCOME MEASURES: Fitness index and exertion perception index was obtained by a cycle ergometer test. Trend analysis was performed on pain scores reported on a visual analogue scale during exertion. RESULTS: Male CPP mean fitness index was found to be significantly reduced. No difference in exertion perception was found between groups. Trend analysis of reported pain revealed that 49% of CPP showed a positive trend, 5% a negative trend, and 46% showed no significant trend as exercise intensity increased. There was no significant relation between type of trend and fitness nor exertion perception index. CONCLUSIONS: Only male CPP have a reduced work capacity. Exertion perception seems normal among CPP. The possible distortion of exertion perception as a causal factor in the reduced fitness of CPP has to be rejected. Lack of significant correlation between type of trend of pain while exercising on a cycle ergometer and fitness index shows that one should be careful in proposing that reduced fitness is only related to pain enhancement during exercise in CPP.