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Exercise Capacity and Immune Function in Male and Female Chronic Fatigue Sydrome (CFS) Patients

Snell, Christopher R.1; VanNess, J. Mark1; Stevens, Staci R.2; Mills, Jarrod M.1

Medicine & Science in Sports & Exercise: May 2004 - Volume 36 - Issue 5 - p S306
Annual Meeting Abstracts: G-28 – Free Communication/Poster: Exercise and Chronic Illness/Injury

1University of the Pacific, Stockton, CA.

2Workwell Foundation, Ripon, CA.



Hyperactivition of a protein (RNase L) central to immune function has been linked to reduced exercise capacity in persons with CFS. However, these findings may be confounded by a failure to adequately control for gender differences in exercise capacity when the results of exercise testing are a primary outcome measure.

PURPOSE: The purpose of this investigation was to compare the exercise capacities of CFS patients with upregulation of the RNase L pathway to those of CFS patients with normal regulation, while controlling for gender. METHODS: Blood was collected from male (n = 35) and female (n = 71) CFS patients to determine immune status. All patients performed graded exercise tests to voluntary exhaustion. Measures of peak VO2, percentage of peak heart rate, body mass index, rating of perceived exertion, and respiratory quotient were entered into a two-way factorial analysis with gender and immune status as the independent variables. RESULTS: A significant multivariate main effect was found for immune status, Wilks' Lambda = 0.85, F (5, 98) = 3.34, P < 0.01. No gender effect or interaction was observed. Follow-up univariate analyses, with alpha levels adjusted to protect against Type-I errors, revealed significantly lower peak VO2 for the upregulated RNase L group (18.9 vs. 22.8 ml/kg/min), F(1, 102) = 12.83, P < 0.01. No other variable differed significantly between groups (P> 0.01). CONCLUSIONS: Abnormal immune activity appears implicated in the pathology of exercise intolerance in some CFS patients. This effect remains evident even when potentially confounding gender effects are taken into account.

©2004The American College of Sports Medicine