One Hard Set
Keep making progress on the weeks you have no time.
Training plans assume you have an hour. In the weeks where you have twenty minutes, most people do nothing at all, and that is what actually costs them.
Most of a set's growth signal comes from the reps near the limit, and one hard set beats no session by a mile. It is not close to free, though: the evidence is fairly consistent that three sets build meaningfully more than one. Treat this as a floor for chaotic weeks, not a substitute for a real session.
Warm up properly, then one set
Two or three light build-up sets, then a single set taken close to failure. The warm-up is not the part to skip.
Take it genuinely near the limit
One or two reps left, not five. This only works because the set is hard. A comfortable single set does very little.
Three movements, fifteen minutes
A push, a pull, a leg movement. That is the whole session.
Log the number
Weight and reps, written down. Without it you cannot tell whether you are progressing or just showing up.
Go deeper
What the paid version adds to this one.
How close to failure is close enough, which is the thing everyone gets wrong
How to cycle this with full sessions across a year
The movement choices that work best when you only get one set
Filmed sessions showing what a genuinely hard set looks like