Buy a watch and it will happily divide your run into five or six coloured zones. That is useful if you know what to do with the colours. Without them, most people simply run their easy days too fast and their hard days not quite hard enough.
There is an older, cheaper instrument: your own voice.
How the test works
During steady effort, try saying a full sentence out loud.
- You can speak comfortably: genuinely easy, conversational pace.
- You can manage short phrases but not a sentence: moderate, somewhere around a tempo effort.
- Single words only: hard.
For the bulk of easy aerobic work, the first line is the target. If you are with someone, a conversation that never needs to stop for breath is the whole prescription.
Why easy days drift upward
Easy pace feels too slow to count as training, so it quietly becomes moderately hard. That effort is still useful, but it costs more recovery and is harder to repeat three or four times a week. The result is a week where every session lands in the same middling grey zone.
Going slower often feels like doing less while actually making the rest of the week possible.
Where it meets the calculator
The activity multiplier in a TDEE estimate describes your week, not the colour of one run. A single hard interval session does not turn a desk job into a high-activity week, and a slow walk does not need to be “earned back” with less food.
If you change your training volume substantially and keep it up for more than a couple of weeks, that is when the activity level is worth revisiting — not after one enthusiastic Sunday.
A workable week
Two or three conversational efforts, one session where you deliberately push a little, and the rest ordinary movement is enough for most people. No zone chart required.
The test is not precise, and it does not need to be. It prevents the single most common mistake: turning every easy day into a test.