By Cort Johnson on September 17, 2013:
While I cannot predict exactly how those with ME/CFS will respond to the cardiopulmonary exercise tests (CPET), I do know that the response is likely to be abnormal in one of several ways. Most often, ME/CFS patients are unable to reproduce maximum oxygen consumption (VO2max) achieved on test 1 during test 2.
It is well documented that healthy subjects are able to reproduce VO2max within 6-7% variation or less, whereas ME/CFS patients usually exhibit a drop in VO2max presumably due to metabolic anomalies that follow test 1, which we call post-exertional malaise (PEM). We don’t know why this occurs; but for one with ME/CFS, it certainly helps to validate claims of fatigue, brain fog, pain, etc., when this VO2max decrement occurs.
The gas exchange measurements made during the CPET also provide a metric of the functional decrement experienced by the ME/CFS patient after post-exertional malaise has occurred, which is why a two-test CPET protocol is necessary if one wants to document a PEM-related decrease in physical function.
Other abnormal responses sometimes include a decrease in anaerobic threshold (AT) from test 1 to test 2, which means that, when fatigued, a person with CFS will have an even lower threshold for physical activity.
Additionally in some cases, because the nervous system does not communicate appropriately with the cardiovascular system in ME/CFS (autonomic dysregulation), differences in the hemodynamic response (heart rate, blood pressure) to exercise can occur from test 1 to test 2 as well. In healthy subjects, these variables are quite stable from test 1 to test 2.
Dr. Betsy Keller is an exercise physiologist who regularly puts ME/CFS patients seeking disability through two-day exercise tests. A professor in the Department of Exercise and Sport Science at Ithaca College in New York, Dr. Keller received her M.S and Ph.D in exercise science.
See also: Revalidation Update: why doctors who use or promote CBT or GET for ME/CFS will fail their revalidation
See also: Dr Snell, University of the Pacific, California: ME/CFS patients have a reduced capacity to exercise when they repeat a maximum exercise test one day on – unlike healthy controls
See also: Another cracker from the CBT school of denial: “The bastards don’t want to get better”…