Focus techniques

Honest, cited guides to named focus methods. What the technique actually says, what the research supports, and when it doesn't fit the work.

52-17 Draugiem Group / DeskTime, 2014 Draugiem Group's 2014 DeskTime analysis: the top 10% of users worked ~52 min and broke ~17 min. A middle ground between Pomodoro and deep work.
90-Minute Ultradian Nathan Kleitman's Basic Rest-Activity Cycle (1963) Work in 90-minute blocks aligned with Kleitman's ultradian cycle. Fits deep knowledge work; the neuroscience is usually overstated in productivity writing.
Deep Work Cal Newport, Deep Work (2016) Cal Newport's scheduling philosophy built on long uninterrupted focus blocks. Fits skill-progression roles; fights responsiveness-heavy ones.
Flowmodoro Community-evolved Pomodoro variant (circa mid-2010s) A flow-state-first Pomodoro variant. Work until focus breaks, then take a break proportional to the session length.
Pomodoro Francesco Cirillo, late 1980s Francesco Cirillo's 25-minute work / 5-minute break method. Great for starting hard work; weaker for flow-state deep work.