Exercise Testing Uncovers Abnormalities in CFS
To gain a better understanding of the pathophysiology of CFS, a research team funded by the CFIDS Association and led by Dr. Mark VanNess and Dr. Christopher Snell from the University of the Pacific is exploring a variety of effects resulting from exercise challenge.
CFS patients can generally perform a maximal exercise test with results similar to sedentary but otherwise healthy individuals. But crucial differences emerge when additional testing is performed within the same 24-hour period. This team is using a “test-retest” strategy to study postactivity symptoms in CFS in order to better characterize what’s going on following exertion and why.
In three presentations at the recent IACFS conference, Snell and VanNess shared findings from their research on this topic. For example, in their exploration of postexertional malaise, CFS patients and matched sedentary control subjects underwent a graded cardiopulmonary exercise test followed by a series of measurements at various intervals following the test. Subsequent analysis revealed that within 24 hours of the exercise challenge, 85 percent of the control subjects had recovered from the exertion but none of the CFS patients had. At 48 hours, the remaining control subjects were fine, while only one of the CFS patients had recovered.
This delayed recovery response is distinctly different from that of sedentary but otherwise healthy people. The results also confirm that postexertional malaise is an incapacitating feature of CFS.
Another aspect of the study compared metabolic and immunologic reactions to exercise. Cardiopulmonary analysis during the exercise challenge demonstrated that significant metabolic abnormalities exist in people with CFS. The CFS patients scored lower than control subjects on measures of peak workload, peak ventilation and peak oxygen consumption and they exhibited a lower threshold at which the body shifted to anaerobic energy conversion. Measures of immune function resulting from the exercise challenge failed to show any clear differences between the groups.
The research team also examined cognitive performance in CFS patients using computer-based measures of reaction time taken before and after cardiopulmonary exercise testing. They found that the CFS patients showed slower reaction times across the board compared to sedentary but otherwise healthy controls. In fact, the CFS patients not only showed slowed reaction time immediately following exercise challenge but also exhibited lingering effects 24 hours later.
The results of these tests underscore biologic abnormalities in patients with CFS and point to the effectiveness of assessing CFS disability and dysfunction at various intervals following an initial exercise test, including running the exercise test a second time 24 hours later to more accurately measure physical limitations.
The CFIDS Association, through your donations, provides the largest source of CFS research money aside from the federal government. We’ve funded nearly $4.7 million in research, but we can do more with your help.
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