What is training monotony, and why does it matter?
Mean daily training load divided by its standard deviation across a week. Values above about 2.0 associate with overtraining, because they mean every day looks the same.
Foster's monotony metric asks how varied your week is, not how hard. Take the daily load values across a week, divide the mean by the standard deviation, and you get a number that rises as the days become more similar. A week of seven identical moderate runs scores high monotony; a week alternating hard sessions and genuine recovery days scores low.
The finding that made it interesting is that high monotony associates with illness and overtraining independently of total load. In other words, a moderate week run identically every day can be more damaging than a harder week with real variation in it — because the easy days are what allow adaptation to the hard ones.
Foster combined it with load into a strain measure: weekly load multiplied by monotony. That captures the case that worries coaches most, which is a high-volume week with no variation at all.
The practical remedy is uncomfortable for a lot of recreational runners: make the easy days easier. Monotony rarely gets fixed by adding harder sessions; it gets fixed by letting the low days actually be low, which is the same prescription that fixes intensity distribution.
Key numbers
| Warning threshold | >2.0 | associated with overtraining |
|---|---|---|
| Formula | mean ÷ SD of daily load | across one week |
Work it out for yourself
Marathon periodization planner — Check monotony and strain alongside fitness and fatigue across your block.
Frequently asked questions
How do I reduce training monotony?
Make the easy days genuinely easy and take at least one full rest or very light day per week. Adding variation at the hard end raises load without reducing monotony much; creating real contrast between hard and easy is what moves the number.
Is a rest day necessary every week?
Not universally, but a very light day serves the same purpose. What matters is that some days differ substantially from the others — a week without contrast is the pattern the metric flags.
Sources
- Foster (1998). Monitoring training in athletes with reference to overtraining syndrome. Medicine & Science in Sports & Exercise.
- Foster et al. (2001). A new approach to monitoring exercise training. Journal of Strength and Conditioning Research.
Related explainers
Glossary: Monotony (Foster)