Best time to work out? BJ Fogg says: right after something

The best time to work out is the one you'll keep, and that's usually a slot tied to something you already do every day. No physical activity guideline names a best hour. Choose the moment your session will follow, write it as "After I…, I'll…", add a back-up slot for the days it's taken, and make the start easy.

BJ Fogg, a behavior scientist at Stanford University, had a model of behavior that already covered motivation and ability. What was missing was the trigger. Then, as Fogg told a TEDxFremont audience in 2012, one day after the gym, a shower and a trip to the sock drawer, "it hit me. After. The secret was after" (TEDxFremont, 13:24). "If you use an existing behavior in your life and you put the new tiny behavior after it, you can use the existing behavior to be the trigger." No reminders, no alarms: you decide what the new habit comes after.

That answers a question people put to search engines as a clock question. "Morning or evening?" matters less than "after what?" A session tied to something that happens every day gets started. A session that floats ("sometime this afternoon") gets pushed to later, then to another day.

Wendy Wood, a psychologist at the University of Southern California who studies habits, lived the floating version for years. With two young sons and a full-time job, the plan was a run at four o'clock, "and then one of them gets sick or another has a friend who comes over," Wood told Shankar Vedantam on Hidden Brain (36:16). "Something always comes up." What worked was a slot nothing else claimed: six in the morning.

Below, you'll choose a cue, write the plan in one sentence, make the first minute easy and keep a back-up for the weeks that move.

Choose the moment, then the hour

1. Let go of morning versus evening

Physical activity guidelines tell you how much and how hard, and stay silent on when. The UK Chief Medical Officers' report, for example, says "any activity is better than none" and that activity can come in bouts of any length (UK Chief Medical Officers, 2019). Nothing in it sets an hour.

So choose by your day, not by a rule. Elizabeth Filips, a medical doctor and YouTube creator, describes being "groggy and miserable" in the mornings and is firm on the other side: "you absolutely can have an effective workout in the evening" (YouTube, 16:39). (The video is sponsored by a coaching app, which Filips says in it.) Wood's answer was the opposite hour for the same reason: it was the one the day couldn't take away.

Look at last week and mark the hours that were yours more than three days out of five. That's your shortlist.

2. Pick a cue that happens every day you plan to move

From the shortlist, choose the moment, not just the hour. Good cues are things you already do without thinking, at roughly the same point in the day:

• after dropping the kids at school
• after the last meeting or call of the day
• after getting home, before sitting down
• after the morning coffee
• after lunch, on days you work from home

The research points at the start of the session as the part a habit takes over. In a month-long diary study of 123 adults, the habit of starting, set off by a cue, was the only habit that predicted how often people exercised; doing the workout itself out of habit added nothing (Phillips and Gardner, 2016). So the cue does the work at the moment it matters most: deciding to begin.

Write the plan where you'll see it

3. Write it as one sentence: "After I…, I'll…"

Fogg's format is that sentence. Make yours specific enough that a stranger could tell whether you did it: "After I close my laptop on Tuesday and Thursday, I'll change and walk for 25 minutes." "After the school drop-off on Monday, Wednesday and Friday, I'll take the long way home."

Planning when and where helps, by a modest amount. In a review of 35 trials, planning raised how active people were; plans made face to face had the clearest effect, and plans delivered by phone, email, text or app showed no clear effect. Plans helped more when people went back to them (Peng et al., 2022). So write it on paper or in your calendar, then reread it on fixed days. Our guide to implementation intentions covers if-then plans in general, and how to make exercise a habit puts the slot inside a full routine.

Set a pace you can keep: for most sessions, you can talk but not sing, the NHS's rough guide to moderate effort (NHS). Stop if anything hurts or you feel unwell.

4. Make the first minute easy

Wood's other trick from those early runs: "I actually slept in my running clothes because it made it easier to then get up and just get out the door early in the morning" (Hidden Brain, 37:22). Earlier in the same episode Wood sums up the research: "people are most likely to repeat actions that are easy for them and actions that are fun" (24:38).

You don't need to sleep in your kit. Take one step out of the start: shoes by the door, the bag packed the night before and left where you'll trip over it, the route or the video chosen in advance. The cue fires; there's nothing left to decide.

Plan for the week that moves

5. Keep a back-up slot, and a short version

Fixed slots get taken. A study at Google tested how rigid a slot should be. In a four-week field experiment, 2,508 employees who wanted to use the workplace gyms each picked a daily two-hour window. Some were rewarded only for visits in a fixed two-hour window; others were rewarded for visits at any time. The flexible groups made more visits, and among people not paid for the window, only about half of their workouts (51%) fell inside the window they had picked (Beshears et al., 2021). It was one employer, with cash rewards for gym visits, so take it as a direction: people are poor at predicting their best slot, and a rigid one costs sessions.

So write a back-up into the same sentence: "After I close my laptop, I'll walk. If a meeting runs late, after dinner." And keep a short version for days when even the back-up shrinks, such as ten minutes around the block. Both count. Our guide to short workouts explains why ten minutes isn't wasted.

If your weeks change shape, as with shifts, travel or caring, anchor to events instead of hours. "After my first shift of the week" or "after the kids' bedtime on nights I'm home" moves with the week. Take five minutes on one fixed day to place the coming week's sessions on the days that have room.

And when a session is missed anyway, plan the slot after it: the short version, no catching up. Getting back into exercise shows how.

If you're starting after a long time off, the NHS suggests speaking to your GP first. WHO guidance says that for light to moderate activity, like brisk walking, that's generally not needed (WHO). If checking would put your mind at rest, do. If you get chest pain or feel faint when active, have a heart condition, or a doctor has told you to limit activity, check with a doctor first, then come back to your plan.

Back to the sock drawer

Fogg's insight came standing at a sock drawer after a shower: the old habit could carry the new one. The best time to work out follows from that. It's whatever comes right after something your day already does, with a back-up for when it doesn't. Choose the moment tonight, and write the sentence where you'll see it tomorrow.

To build this around your own week, try the 1h Protocol to Build an Exercise Routine, a program of practical education. Its free first chapter starts with a quick check, asks how your last try went and how it ended, and finds your pattern (one of five, or the Tune-up). If the session kept getting pushed, your pattern may be the Floating Slot, and your first step is tying it to a moment you never skip. The full program takes about an hour: seven chapters build one session with you, from your slot and its cue to the tick after it, with a back-up, then plan the slot after a miss and set up your week. You leave with up to three changes to start now, each with an alternative, a log that counts the week with planned skips, your slots in your calendar and reviews on days 7, 14 and 30. Four one-tap check-ins follow by email on days 1, 7, 14 and 30, if you're signed in. Start free

Frequently asked questions

Is it better to work out in the morning or the evening?

Neither, for most people building a routine. Physical activity guidelines set how much and how hard, not when (UK Chief Medical Officers, 2019). Pick the time you can keep on most weeks. Elizabeth Filips, who isn't a morning person, says "you absolutely can have an effective workout in the evening" (YouTube, 16:39).

What is habit stacking?

It's the popular name for BJ Fogg's "after" rule: put a new habit right after one you already do, so the old one becomes the cue. "After I pour my morning coffee, I'll put on my shoes and walk for ten minutes" is one example. Fogg's talk lays out the idea (TEDxFremont, 13:24).

What if my schedule changes every week?

Anchor the session to an event instead of a clock time, such as "after my first shift of the week", and plan the coming week's sessions on one fixed day. In a study of 2,508 Google employees, a rigid two-hour window gave fewer gym visits than flexible timing (Beshears et al., 2021).

What should I do when my workout slot gets taken?

Use your back-up slot if you wrote one. If that's gone too, do the short version, such as ten minutes, or let the session go and come back at the next slot without catching up. See getting back into exercise.

How do I make it easier to start?

Take one step out of the start. Lay out shoes and clothes, pack the bag the night before, and choose the route or video in advance. Wendy Wood once slept in running clothes to get out the door early (Hidden Brain, 37:22). Keep the pace easy enough to talk, and stop if anything hurts or you feel unwell.

Sources

This article draws on BJ Fogg's TEDxFremont talk, Wendy Wood's interview on Hidden Brain, Elizabeth Filips's video on quitting the gym, and the studies and guidance listed below.

• Forget big change, start with a tiny habit: BJ Fogg at TEDxFremont (TEDx talk, 2012)
• Creatures of Habit, with Wendy Wood (podcast episode, Hidden Brain, 2019; minutes from the 2021 rebroadcast)
• Elizabeth Filips, Why You Always Quit the Gym (YouTube video, sponsored, 2023)
• Phillips and Gardner, Habitual exercise instigation (vs. execution) predicts healthy adults' exercise frequency (one-month diary study, 123 adults, 2016)
• Peng et al, The effectiveness of planning interventions for improving physical activity in the general population (meta-analysis, 35 randomized trials, 2022)
• Beshears et al, Creating exercise habits using incentives (randomized field experiment, 2,508 Google employees, four weeks, 2021)
• UK Chief Medical Officers, Physical activity guidelines (government guideline, 2019, updated 2026)
• NHS, Physical activity guidelines for adults aged 19 to 64 (health information page, 2024)
• World Health Organization, Guidelines on physical activity and sedentary behaviour (guideline, 2020)