Cardio in contest prep: how much, when, and where to stop

Every prep throws up the same question in the gym: do you start cardio in week one, or save it for later? The answer is less about minutes and more about order of operations — cardio is the tool you reach for once food and training have stopped doing the job on their own. Spend it too early and you have nothing left to give when the scale digs its heels in.

What cardio actually does in a prep

Cardio does not burn body fat directly. It raises daily energy expenditure, which lets you hold a deficit without cutting food any further. That difference matters in practice: the same 300-calorie gap can come off your plate or out of 45 to 60 minutes of walking, and food is also what fuels your training.

This is why most experienced competitors work in the same sequence — set the intake, watch the rate of loss for a couple of weeks, then add cardio only when weight stalls. A realistic pace is roughly 0.5 to 1 per cent of body weight per week, which we cover in more detail in the piece on how fast fat actually comes off before a show.

There is a third benefit that gets forgotten. Decent conditioning means that deep into a diet, a set of squats is not a fight for air between reps. In the last month, that is not a small thing.

Where to start and how to add

If you are running a 16-week prep, start light: two or three sessions of 20 to 30 minutes of easy cardio a week, or simply a daily step target. Anything more at the beginning means less room to manoeuvre by week ten. The full shape of a prep is laid out in our guide to what 16 weeks realistically looks like.

The rule for adding is straightforward. Change something only when weight has not moved for two consecutive weeks, judged on the weekly average rather than one bad morning. Then either add one session or extend the existing ones by ten minutes — not both at once, or you will never know which worked.

For most people the ceiling sits somewhere between four and six hours a week, and only in the final month or two. Past that you tend to pay in strength, sleep and appetite control, and the fat does not come off any faster.

Steady state, intervals and steps

Easy steady-state work — walking, a stationary bike, a cross-trainer at a pace where you could still hold a conversation — is the backbone. You recover from it easily and it interferes least with leg training. If you only pick one type, pick this one.

Intervals save time but they are not free. One or two short sessions a week is plenty for most, and they have no business sitting the day before or straight after heavy legs. Hill work and the bike are far kinder to the joints than road running; if your knees already grumble, it is worth reading what genuinely helps with knee injury prevention.

Steps are the most underrated tool of the lot. A baseline of eight to twelve thousand a day burns a serious amount of energy while barely registering as training. For a lot of competitors, that is the difference between a prep that holds together and one that falls apart in the last month.

Timing, and the fasted question

The cleanest arrangement is to separate cardio and lifting — one in the morning, one later — so neither eats into the other. If that is not practical, cardio goes after the weights. Put it first and you spend exactly what the heavy sets needed.

Fasted cardio has no clear advantage for fat loss once total intake is matched. Some people like getting it done before breakfast and off the list; others run out of steam after twenty minutes. Both work, so choose the one you will still be doing in week twelve without negotiating with yourself every morning.

How to tell it has become too much

The signs are fairly consistent, and they rarely turn up alone:

• Working weights drop 10 to 15 per cent in a couple of weeks, faster than the deficit explains.
• Resting heart rate creeps up, sleep gets shorter or broken.
• Hunger becomes unmanageable and you stay wired long after training.
• Joints, shins and Achilles tendons start to niggle.
• The scale sits still even though you have already increased cardio twice.

That last one is the important one. When adding cardio stops producing anything, the correct move is to pull it back and give yourself a few days with more food and fewer sessions — not to bolt another hour onto the treadmill. You cannot out-work accumulated fatigue.

The final week and what comes after

Cardio is usually cut back sharply or dropped entirely in the last few days, because that stretch is about muscle fullness and a settled body, not further expenditure. What actually happens in those days is covered in our piece on peak week in practice.

Afterwards, do not stay on five or six hours a week while food climbs back up. Drop to two or three sessions of 20 to 30 minutes and keep them through the off-season — partly for heart health, partly because the next prep then starts from a much lower number instead of an already maxed-out one.

When to see a doctor

Chest pain or tightness during effort, fainting, dizziness, a fluttering or racing heartbeat, or breathlessness during easy walking are not things a rest day fixes. The same goes for a resting heart rate that stays unusually high for weeks, swelling in the legs, or pain that shows up in the same spot every single session. Get it looked at before you carry on with the prep.

The short version

• Food creates the deficit; cardio is the lever that keeps it moving once the scale stalls.
• Open with two or three sessions of 20 to 30 minutes a week and add only after two flat weeks.
• Make one change at a time: either an extra session or ten extra minutes.
• Steady state and steps are the base; keep intervals to once or twice a week and away from leg days.
• Falling strength, poor sleep, a high resting pulse and a stuck scale despite more cardio all mean cut back, not add.