The aim of this study is to determine whether patients presenting with long-COVID meet chronic fatigue syndrome (CFS) characterisation criteria and to then compare autonomic function in patients with long-COVID and patients with CFS.

A series of questionnaires and an interview with a trained member of the team will be conducted to characterise fatigue and other symptoms, and to determine eligibility for the study prior to a lab visit. If appropriate, the participant will visit their GP to complete a checklist that eliminates other causes of fatigue.

During the lab visit, the participant will perform a series of 2-minute tasks whilst lying on their back. The tasks include moderate force handgrip exercise, Stroop test (colour-word computer game), and cold pressor test (immersion of hand in icy water). This is followed by a tilt-table protocol where participants will be tilted upright (5min at 30 degrees, 5min at 45 degrees and up to 30min at 60 degrees).

The participant can stop or withdraw from the study at any time. Throughout the protocol several continuous measurements will be made, including heart rate, blood pressure, respiration, and nerve activity. The total time in the lab is usually 2-3 hours. Participants are reimbursed for their time in the lab.

Benefits:

• Potential to better understand neurological disturbances in long-COVID and chronic fatigue syndrome, which could lead to better intervention in the future

• There is no direct benefit to the participant as this is not a clinical trial