How to log cardio without lying to yourself

Cardio logging goes wrong in a specific way: people record the one number that is least reliable and skip the ones that actually show progress.

Do not log calories burned

Machine and wearable estimates of energy expenditure are built from population equations using speed, resistance, your weight and sometimes heart rate. They commonly differ from measured values by 20 to 30 per cent, and the error is not symmetrical — they tend to read high.

That matters because a number in a log becomes a number you act on. Six hundred calories that were really four hundred, eaten back after the session, turns a deficit into maintenance. The full case is in are the calories-burned numbers worth anything.

There is also a second-order problem. Treating exercise as a way to earn food produces a relationship with both that tends to end badly, and it is the mechanism behind a lot of the compensation described in breaking the restrict-and-binge cycle.

What to log instead

Type. Run, cycle, row, swim, walk, stair climber. Consistently named.

Duration. Minutes. The most reliable field you have.

Distance, where it applies. Kilometres for running and cycling, metres for rowing and swimming.

Perceived effort. The same 1 to 10 idea as in lifting, though here it describes cardiovascular strain rather than proximity to failure. "Could hold a conversation" is about 4; "could speak in short sentences" is about 6; "could not speak" is 9.

Heart rate, if you have it and find it useful. Average is more informative than peak.

How cardio progress shows up

Three signals, all visible from those fields.

More distance in the same time. The obvious one.

The same distance at a lower average heart rate. The clearest sign of improved aerobic fitness, and it is often the first to move.

The same session at a lower perceived effort. Real progress that requires no equipment to detect.

Comparing these across four-week blocks rather than session to session is the same discipline as for lifting, for the same reason — daily variation is larger than weekly progress. See how to read real progress out of a training log.

Steps matter more than sessions

For most people, the daily step count is a more consequential number than any single cardio entry.

Incidental movement across a whole day — walking, standing, stairs, errands — typically contributes more to daily expenditure than one gym session, and it is the component that quietly falls when someone starts dieting. That mechanism is explained in steps, NEAT, and the calories you burn standing up.

A step target is crude and it is visible, which makes it useful in a way that a calories-burned estimate is not.

Cardio alongside lifting

Two practical notes for anyone doing both.

Separate them where you can. Hard cardio immediately before lifting reduces the load you can handle; hard cardio immediately after adds fatigue to a session that already produced some. A few hours apart, or on separate days, is better if your schedule allows it.

Low-intensity work interferes least. Walking and easy cycling add expenditure without meaningfully compromising strength training recovery. Long, hard intervals do compete, particularly for the legs.

If your lifting numbers start falling after adding cardio, the log will show it before you feel it, and the usual fix is to reduce the intensity of the cardio rather than to stop.

What cardio is actually for

Cardiovascular health, work capacity, and enjoyment — all of which are good reasons on their own.

As a fat loss tool it is modest relative to how it is marketed: an hour of moderate cardio is a few hundred calories, which is one snack. It works best as a supplement to a calorie deficit rather than as a substitute for one, which is the framing in how to lose fat without quitting in three weeks.