See the whole shape of your running fitness.

Your marathon PB is one point on a curve. The power duration curve shows you all of it: where you're strong, where you're thin, and where the next gain is hiding. For runners chasing a number, not a first finish line.

• What the curve actually is — and why two runners with the same marathon time can need completely different training
• Why standard training zones miss — they're a percentage of one number, they ignore how long you can actually hold a power, and they weren't built from your data
• The year-on-year test — lay this year's curve over last year's and get a straight answer to "am I actually fitter?"
• Why your curve goes stale — how one old session ageing out can drop your threshold overnight, and the simple fix that keeps your zones honest

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