Nancy,
I welcome you thoughts on the following:
"http://drmyhill.co.uk/wiki/Exercise_-_the_right_sort_in_Chronic_Fatigue_Syndrome
also the following describes a test of mito function:
"http://www.ijcem.com/files/IJCEM812001.pdf
and another, scroll down to "Review of the “Two-day Exercise Test”:
"http://www.cfsresearch.org/cfs/bell/cfs-mitochondrial-disease.htm
David