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Subclassifying Chronic Fatigue Syndrome through Exercise Testing


Medicine & Science in Sports & Exercise: June 2003 - Volume 35 - Issue 6 - p 908-913
doi: 10.1249/01.MSS.0000069510.58763.E8
CLINICAL SCIENCES: Clinically Relevant

VANNESS, J. M., C. R. SNELL, D. R. STRAYER, L. DEMPSEY IV, and S. R. STEVENS. Subclassifying Chronic Fatigue Syndrome through Exercise Testing. Med. Sci. Sports Exerc., Vol. 35, No. 6, pp. 908–913, 2003.

Purpose The purpose of this study was to examine physiological responses of persons with chronic fatigue syndrome (CFS) to a graded exercise test.

Methods Cardiopulmonary exercise tests were performed on 189 patients diagnosed with CFS. Based on values for peak oxygen consumption, patients were assigned to one of four impairment categories (none, mild, moderate, and severe), using American Medical Association (AMA) guidelines. A one-way MANOVA was used to determine differences between impairment categories for the dependent variables of age, body mass index, percentage of predicted V̇O2, resting and peak heart rates, resting and peak systolic blood pressure, respiratory quotient (RQ), and rating of perceived exertion.

Results Significant differences were found between each impairment level for percentage of predicted V̇O2 and peak heart rate. Peak systolic blood pressure values for the “moderate,” and “severe” groups differed significantly from each other and both other groups. The more impaired groups had lower values. The no impairment group had a significantly higher peak RQ than each of the other impairment levels (all P < 0.001). Peak V̇O2 values were less than predicted for all groups. Compared with the males, the women achieved actual values for peak V̇O2 that were closer to their predicted values.

Conclusion Despite a common diagnosis, the functional capacity of CFS patients varies greatly. Stratifying patients by function allows for a more meaningful interpretation of the responses to exercise and may enable differential diagnosis between subsets of CFS patients.

1University of the Pacific, Department of Sport Sciences, Stockton, CA;

2The Workwell Foundation, Ripon, CA; and

3Hemispherx Biopharma, Inc., Philadelphia, PA

Address for correspondence: J. Mark VanNess, Department of Sport Sciences, University of the Pacific, Stockton, CA 95211; E-mail:

Submitted for publication June 2002.

Accepted for publication December 2002.

©2003The American College of Sports Medicine