Fig. 1

Pre-exercise Dizziness and Lightheadedness Scores. CFS subjects reported significantly more Dizziness and Lightheadedness than controls while supine and standing. Absence of symptoms was reported in 14/25 controls and 6/39 CFS subjects (FET, p < 0.0001). The connected dots indicate trends for Dizziness and Lightheadedness to increase in controls and CFS when standing up. Black bars indicate p < 0.05 by Mann–Whitney U test between CFS and controls for supine and standing symptoms