"CFS patients have low normal level of fitness" I think this 1996 study by Sisto is fairly typical of research on VO2max levels of CFS patients, with exception of the large De Becker study. The controls weren't really sedentary, but the VO2max levels of theCFS patientsare interesting. They were divided into the 40% that acheived maximal exertion ("Max",within 10bpm of age-predicted heart rate and RQ>1), and 60% that did not. Nb no verbal encouragement was given during the testing as the testers didn't want to overstress patients. VO2 'max' ml/min/kg "Max" patients: 28.1 (for women, 26-29 is 'fair', 30-33 is average) no-Max patients: 23.9 All: 25.9 We do know something about the patients: 22 women with a mean age of 34 and none had been ill for more than 4 years; 50% were unable to work, 29% could only work part-time and presumably the remaining 21% could work full-time. I'm not sure, but I think this is a fairly typical work pattern for patients in CBT/GET trials, and, as the authors point out, they are not very fit, but not deconditioned either. Which is interesting as deconditioning is a key assumptions of both CBT and GET. If anyone has data on typical work status of trial participants, please do post details.