fatigue

Long COVID patients can experience severe energy crashes after physical exertion. New research provides clear evidence that there's a biological basis for the symptoms.

Research finds that triathletes who train too hard can impair a brain area involved in achieving goals such as winning a race. Fatigued athletes choose immediate gratification over long-term rewards.

Avoiding your phone and TV at night and setting a firm bedtime might solve your problem if you feel tired a lot. But fatigue can also be a sign of disease.