No motivation to exercise: it shows up once you start.

'I've got no motivation to exercise.' It's half six, your last call is done and you say it to yourself in the car. You pop home to drop off your laptop, sit down for a minute, and the evening's gone.

I hear it a lot, usually with a hint of shame. Even from people with years of training: 'I just can't be bothered any more.' It's rarely laziness. It's a planning problem: you're asking motivation to turn up first, and it turns up afterwards.

Low motivation or real tiredness: how to tell them apart

• Low motivation lifts once you start. After the warm-up you usually feel better than before.
• Real tiredness stays. Your usual weights feel heavier, and session after session you lift less.
• Mornings and mood. Waking up drained and irritable for days often means you're doing more than you can recover from.

Why motivation comes after you start

Starting is the hardest part. Your brain saves energy, and by evening every extra decision is an effort. Sofa or gym, whichever asks less wins. Once you're moving, your body usually follows.

The reward comes afterwards. Straight after a session, dopamine, serotonin and noradrenaline rise. They're the chemicals behind mood and drive. Waiting until you feel like it is waiting for the effect before the cause.

Willpower is for the beginning. Almost half of what you do in a day is thought to be habit, things you decided once and stopped deciding. How do you build a new habit? By repeating it. Many people need a couple of months, and by the second or third, starting usually feels far easier.

What do you do when you have no motivation to exercise?

Start with five minutes, then decide whether to carry on. Sort your time, bag and minimum version the day before.

The five-minute rule. Get changed and do five minutes: a warm-up and one set of your first exercise. Then you can stop. Often you'll stay, because the hard part was starting.

Tie the session to something you already do. Pick something you do on autopilot, like closing your laptop or leaving the office. Write it down: 'After I close my laptop, I go and train.' That's one less decision.

Get everything ready the night before. Gym bag by the front door, or already in the car. Then go straight from work. Call in at home and you'll probably stay.

A fixed time, in your diary. Same days, same time, like a meeting. After a while, the time itself becomes the cue. Which time? See my article on morning or evening exercise.

Three versions of the same session. Full, the one in your programme. Short, ten minutes. Minimum, five squats. On a bad day you do the minimum, and it counts. Missing a session happens. Just turn up for the next one.

If it's real tiredness, rest. After too little sleep or a heavy training week, go for a walk and get to bed earlier. Recovery is part of training: it's when your body rebuilds. Then go back to your usual time: long breaks undo some of what you've built.

Tonight, put your gym bag by the door and the time in your diary. On Thursday, if the motivation isn't there, do the first five minutes.