Plain Words
Running data, in plain words.
Runners are not short of numbers. A modern watch produces training load, recovery time, a fitness score, a race prediction, seven heart-rate zones and a verdict on whether last week was productive — and almost none of it comes with an explanation you could check. So the questions that fill running forums are not about training theory. They are about arithmetic nobody will show you: my heart rate hit 180 on an easy run, is that dangerous? My fitness score fell while I got faster, what is it measuring? My watch says 3:18 and the app says 3:47, which do I pace off?
This is where those get answered, with the number first and the reasoning underneath.
Every piece here follows the same shape, because it turns out to be the shape that actually helps. The complete answer sits in the first forty to seventy words, so you can leave immediately if that is all you needed. Then a table of the figures worth comparing. Then the sections, each one a question somebody actually typed, answered in two or three sentences before any elaboration. Then a decision rule — the if-this-then-that you can use at six in the morning without re-reading anything. Then the sources, dated, primary literature first.
What you will not find is padding. There is no advertising on this site and no affiliate revenue, so there is no reason to stretch a short answer into a long one. Some of these pieces are 900 words because the question is worth 900 words. None of them are long to make room for a banner.
Two habits are worth naming because they are unusual. First, where the evidence genuinely contradicts itself — fuelling, taper length, how much heat costs you — the page says so, names the studies on both sides, and still gives you a rule. Second, where we do not know, the page says we do not know. That sentence appears here more often than it does anywhere else in running, and it is the most honest thing on the site.
Pieces are grouped by pillar below. If you arrived looking for a specific number rather than an explanation, the tools and pace pages go straight to it, and the glossary defines every metric in one sentence.