In plain English
Monotony measures how little your daily training load varies across a week. Strain combines that with total load. High values mean hard days with no real easy days between them.
What it is
Carl Foster proposed two simple measures alongside weekly training load:
- Monotony = the average daily load across a week ÷ the standard deviation of that daily load. If every day is similar, monotony is high. If hard days alternate with genuinely easy days, it’s low.
- Strain = weekly load × monotony.
Daily load is often worked out with session RPE (how hard the session felt × minutes), but the same maths works with other load scores.
Why it matters for training decisions
In Foster’s 1998 study of 25 experienced athletes, a high share of illnesses happened when individuals went over their own thresholds, mostly linked to training strain. The practical lesson is to keep real variation in your week. Easy days should be easy enough to let the hard days count.
Limits
That was a small study, and the thresholds were individual rather than universal. Monotony also has a quirk: a week with very little training can still look “monotonous” if every day is equally light. Read it with total load, not on its own.
How P247 uses it
P247 doesn’t calculate a separate monotony or strain score.
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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