In plain English
Fitness minus fatigue (CTL minus ATL). Negative means recent training is heavier than you're used to. Rising towards positive usually means you're freshening up.
Also called: Form (intervals.icu)
What it is
Training stress balance, called Form in intervals.icu, is your chronic load minus your acute load: CTL − ATL. intervals.icu can show it as an absolute number or as a percentage of fitness.
Why it matters for training decisions
- Clearly negative form means your last week or so has been heavier than your six-week average. That’s normal and expected in a build block.
- Form rising towards zero or above usually means you’re carrying less fatigue, for example in a recovery week or taper.
Planning around form helps you avoid stacking too many heavy weeks, and helps you arrive at a race with fatigue cleared while most of your fitness is still there. That’s the logic of a taper.
Limits
Form is a model built on training load alone. It doesn’t know how you slept, whether you’re getting sick or how stressed you are. There’s no universal “right” number for race day, and the best range differs between athletes and between absolute and percentage views. Use it with how you feel, and with HRV and resting heart rate trends, rather than as a target in its own right.
How P247 uses it
P247’s weekly report weighs your training load against your recovery signals instead of relying on form alone.
Read more on the P247 blog
Sources
This glossary is general information to help you understand your training data. It isn't medical advice, diagnosis or treatment. For injury, illness, medication, blood test results or any health concern, speak to a qualified health professional.
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