The instinct when you have no energy is to rest more, and for ordinary tiredness that's right. For the persistent low-level depletion that doesn't resolve with sleep, gentle movement often does more than additional rest — which is counterintuitive enough that most people never try it.
The rest that doesn't restore
Stopping isn't the same as recovering — the body can stay in a low-grade alert state through a whole day of lying down, which is why a weekend of doing nothing can leave Monday feeling identical; that gap between rest and recovery is its own subject, covered in "Why Rest Doesn't Always Feel Restful."
Why gentle movement helps where rest doesn't
Slow movement with attention to breath tends to shift people out of that state. The mechanism is not mysterious — slow breathing with extended exhalation is well established as a way of settling the nervous system.
It's also just circulation and mobility. A body that's been still for a long stretch feels worse than one that's moved a little, and the fix is smaller than people assume.
Why not harder exercise
If you're genuinely depleted, a demanding workout can set you back — it adds a load to a system that's already short.
Qigong sits in a useful place: enough to change your state, not enough to cost you anything. That makes it practical on days when nothing else is.
What's realistic
Many people find regular practice leaves them less flat, sleeping somewhat better, and less braced during the day. That's worth having.
It won't resolve an untenable workload, a sleep disorder, or a medical cause of fatigue. Nothing will, except addressing those directly.
A daily practice
Ten or fifteen minutes most days outperforms an hour at the weekend. Morning suits most people for energy; evening suits those whose problem is switching off.
The simplest version is a short sequence you know well enough not to think about, done at roughly the same time each day.
When to see a doctor
Persistent tiredness that doesn't respond to rest, sleep or exercise has common, treatable medical causes worth ruling out — the signs that it's more than everyday tiredness are covered in "Why Am I Tired All the Time?"