04 February 2008
Diminished Cardiopulmonary Capacity During Post-Exertional Malaise
Journal, J of Chronic Fatigue Syndrome, Vol. 14, No. 2, 2007, pp.
77-85
Authors: J. Mark VanNess PhD, Christopher R. Snell PhD, Staci R.
Stevens
Reduced functional capacity and post-exertional malaise
following physical activity are hallmark symptoms of Chronic Fatigue Syndrome
(CFS). That these symptoms are often delayed may explain the equivocal
results for clinical cardiopulmonary exercise testing with CFS patients. The
reproducibility of VO2max in healthy subjects is well documented. This may
not be the case with CFS due to delayed recovery symptoms.
Purpose: To
compare results from repeated exercise tests as indicators of post-exertional
malaise in CFS.
Methods: Peak oxygen consumption (VO2 peak), percentage
of predicted peak heart rate (HR%), and VO2 at anaerobic threshold (AT), were
compared between six CFS patients and six control subjects for two maximal
exercise tests separated by 24 hours.
Results: Multivariate analysis
showed no significant differences between control and CFS, respectively, for
test 1: VO2 peak (28.4 ± 7.2 ml/ kg/min; 26.2 ± 4.9 ml/kg/min), AT (17.5 ±
4.8 ml/kg/min; 15.0 ± 4.9 ml/ kg/min) or HR% (87.0 ± 25.4%; 94.8 ± 8.8%).
However, for test 2 the CFS patients achieved significantly lower values for
both VO2peak (28.9 ± 8.0 ml/kg/min; 20.5 ± 1.8 ml/kg/min, p = 0.031) and AT
(18.0 ± 5.2 ml/kg/min; 11.0 ± 3.4 ml/kg/min, p = 0.021). HR% was not
significantly different (97.6 ± 27.2%; 87.8 ± 9.3%, p = 0.07). A follow-up
classification analysis differentiated between CFS patients and controls with
an overall accuracy of
92%.
Conclusion: In the absence of a second
exercise test, the lack of any significant differences for the first test
would appear to suggest no functional impairment in CFS patients. However,
the results from the second test indicate the presence of a CFS related
post-exertional malaise. It might be concluded then that a single exercise
test is insufficient to demonstrate functional impairment in CFS patients. A
second test may be necessary to document the atypical recovery response and
protracted malaise unique to CFS.