3 ideas
A single 12-minute weekly session of five compound machine exercises taken to momentary muscular failure. The claim is that intensity, not frequency or duration, drives adaptation, so more volume is counterproductive to recovery.
Lifting a load slowly until no further repetition is possible fully recruits and fatigues muscle fibers in one set. This inroad into the muscle's reserve is the trigger that signals the body to grow stronger.
Exercise is only the stimulus; adaptation happens during days of rest as the body overcompensates. McGuff argues most people are chronically overtrained and would grow more by training less often.