What are ultradian rhythms in plain language?

Ultradian rhythms are repeating cycles inside a day, shorter than sleep. Popular productivity writing often cites roughly 90-minute cycles of higher and lower alertness. The science on exact timing is messier than blog posts suggest, but many knowledge workers find that 60 to 120 minute deep blocks with real breaks between them match how their attention actually feels.

Why does Hush offer 25, 50, and 90 minute focus sessions?

Those three durations map to common real-world uses: a classic Pomodoro-length sprint, a longer desk session before a natural pause, and a block aligned with how some people experience deep work or ultradian-style cycles. The last-used duration is remembered so a global shortcut can restart the same rhythm without opening the menu.

When should you ignore a focus timer?

When you are already in flow on a single hard problem and stopping would cost more than it saves. Timers help starting and accountability; they hurt when they force arbitrary context switches during exploration, writing, or debugging. Better rule: protect the block, not the clock.

Field notes · focus

Pomodoro, deep work,
and when timers lie.

Q: Is Pomodoro always 25 minutes?

The classic Pomodoro Technique uses 25 minutes of focused work followed by a short break. The number is practical, not sacred: it came from Francesco Cirillo's kitchen timer and stuck because it is easy to commit to. Many people later stretch the work block to 50 or 90 minutes when the task needs longer uninterrupted stretches.

Twenty-five minutes is not magic. Neither is fifty or ninety. Here is what those numbers are actually for, when to trust them, and when to throw them away.

Posted May 7, 2026 · ~ 7 min read

Every second productivity app ships the same three presets: Pomodoro (25), “deep work” (45–50), and something around ninety minutes. The labels sound scientific. Usually they are folklore with good UX. That does not make them useless. It means you should know which folklore you are buying.

A.Twenty-five minutes: kitchen timer, not law

The Pomodoro Technique comes from Francesco Cirillo and a tomato-shaped kitchen timer. The unit of work is short enough that starting feels cheap, long enough that you can finish a small slice of something real. Nothing in the original idea requires exactly 25 — it is a default that stuck because humans commit to round numbers.

Where Pomodoro shines: overcoming activation energy, time-boxing shallow tasks (email triage, ticket cleanup), and giving your brain a negotiable finish line so anxiety does not freeze you. Where it struggles: work that needs forty uninterrupted minutes to load the mental stack — debugging, long-form writing, proofreading someone else’s diff. Stop mid-stack and you pay a re-entry tax.

B.Fifty and ninety: deep blocks and wobbly biology

Longer blocks show up everywhere Cal Newport’s Deep Work echoed through tech Twitter: turn everything off, work on one hard thing, emerge hours later. Fifty minutes is a common compromise between “I need runway” and “I need a bio break.” Ninety minutes gets marketed as aligned with ultradian rhythms — cycles of alertness within the waking day.

The sleep research behind ultradian rhythms is solid. The leap from there to “your creative work must fit in 90-minute bricks” is less solid. Brains vary; jet lag, coffee, and meetings destroy any neat periodic table. Treat ninety as a useful upper bound for “I should probably stand up before my spine fuses to the chair,” not as biology homework.

C.When the timer is the enemy

Sophie Leroy’s paper Why is it so hard to do my work? (2009, Organizational Behavior and Human Decision Processes) introduced attention residue: the idea that when you switch tasks before closing the mental loop, part of your attention stays stuck on the old task. A bell that fires because the clock said so can force exactly that switch.

Practical rule: if the timer rings and you are in the middle of a genuine insight or a tight debug trail, finish the thought. The Pomodoro is there to start you and to bound procrastination — not to veto flow. Protect the block you promised yourself, not the minute hand.

D.Why Hush uses 25, 50, and 90

Hush is a menu-bar app for closing idle apps; it also has a small focus session: pick a duration, it clears checked apps except the frontmost one, tightens idle quit while the session runs, and exposes a global shortcut (⌥⌘H) that toggles the same duration you used last.

The three numbers are not mystical. They map to how people actually batch work: a Pomodoro-length sprint, a longer stretch before lunch, and a serious deep-work slab. The app remembers which one you picked last so the shortcut matches your rhythm without extra clicks.

E.Coming later (maybe): Calendar, context, and real breaks

None of this ships yet. Consider it a sketch on the whiteboard, not a promise. If I build it, it will be optional and behind permissions you explicitly grant.

Calendar logging. When you start a focus session, Hush could write a Calendar event for that block: start time, end time, chosen duration, and the name of the app that was in the foreground at kick-off (so Thursday afternoon shows “Focus · 50 m · Xcode” instead of an anonymous blob). macOS would show the usual Calendar access prompt first.
Break blocker. After the session ends, an optional 5–10 minute break mode: gentle guardrails so the first thing you do is not diving straight back into Slack or the same browser tab forest — think Focus filter, full-screen break card, or a simple “break timer” you cannot dismiss in one tap. Exact shape TBD; goal is a real pause, not nanny software.

If that sounds useful or terrible, open an issue on GitHub. Product direction around here is still mostly “what would make a calm Mac calmer.”

Try the timer that already exists

Focus sessions are in the current build: 25, 50, or 90 minutes, plus ⌥⌘H from anywhere. Idle apps get out of the way while you work. No account, no telemetry.

Download Hush for Mac

FAQ

Is Pomodoro always 25 minutes?
Classic Pomodoro uses 25 + short break. The number is practical, not sacred. Stretch or shrink to fit the task.

What about ultradian rhythms?
Real phenomenon; messy to schedule around. Use long blocks when you have energy; insert breaks before you crash, not because a blog said minute 87.

Why three presets in Hush?
They cover short sprint, medium desk session, and a deep slab without turning the menu into a spreadsheet.

When should I ignore the timer?
When stopping would cost more focus than a break would save. Finish the thought; take the break after.

Pomodoro, deep work, and when timers lie.