Long Covid also called “Post-COVID 19 Condition”: Persistence of symptoms for more than 12 weeks following infection with the covid virus, if possible confirmed by a positive test.

Dysautonomia: dysfunction of the autonomic nervous system. The autonomic nervous system regulates the body's various organs automatically and involuntarily (breathing, heart rate, digestion, thermoregulation, etc.), unlike the voluntary nervous system (motricity, walking, movement, etc.).

Long covid causes hyperactivity of the sympathetic nervous system, the body's activating system, which reacts to stress, to the detriment of the parasympathetic nervous system, the body's calming and relaxing system.

Pacing is a strategy and rehabilitation approach that balances rest and activities in daily life, to manage symptoms such as fatigue and post-exertional symptom exacerbation (PESE).

Pacing or activity management is a safe and effective rehabilitation intervention for people living with Long Covid, and may reduce Post-Exertional Symptom Exacerbation (PESE) episodes.

Post-exertional malaise (PEM) Post-exertional symptom exacerbation (PESE) in the context of Covid-19: Usual clinical definition of the symptom:

Post-exertional malaise (or exacerbation of symptoms) is defined as intense exhaustion accompanied by exacerbation, relapse of Covid Long symptoms, or even the appearance of new symptoms, after even minor, previously well-tolerated activity (physical, cognitive and/or social) or stimulus overload (e.g. emotional or sensory). MPE/ESPE rarely appears at the very moment of the triggering event (a physical activity, a daily task or the accumulation of several activities, for example) but more often than not at a later date, the day after, the day after and up to 72 hours after the triggering event or overload. MPE/ESPE, by definition, lasts for more than 12 hours, and can only be overcome with great difficulty/partially with rest.