Generally only limited fatigue in healthy individuals after long-term bed rest Given the arguments about deconditioning, I had expected to find frequent reports of fatigue in studies of healthy volunteers who took to their beds for many months. But it turns out there are very few mentions of fatigue, though it wasn't specifically studied. As this type of research was mainly undertaken to understand the negative effects on astronauts abilitiy to work in space, fatigue probably would have been reported if it had been a signifcant issue. One very long-term study (n=5, 5.5-7 months) did comment that after bed rest: which reinforces the impression that fatigue is a minor side-effect even after spending 6 months in bed. An even longer term study (n=3, 7-8.5 months) did not: so perhaps spending well more than 7 months in bed can cause significant fatigue. Again, the evidence suggests that the level of resting undertaken by CFS patients regularly able to attend clinics as outpatients is unlikely to cause significant fatigue through deconditioning. For completeness, I did find one significant meantion of fatitgue was in a shorter, 70-day study. There were 15 subjects spread over 5 series (experimental groups); Series 1 had no 'countermeasures' such as exercise, so should lead to the most deconditioning - and there was no mention of fatigue. There were mentions of fatigue after the bed rest for series II, and during for series III and IV but no details are given of the countermeasures. Possibly the countermeasures contributed to the fatigue, particularly as other, much longer, bed rest studies did not report fatigue: Aside from these studies I couldn't find any mention of fatigue at all in the bed rest literature (as searched on google), so I assume it isn't a significant issue.