Training Monotony
Training monotony describes how similar daily training load is across a week and helps identify overly uniform training structure.
Training Monotony & Training Strain
Besides the absolute size of training load (TSS, CTL), it’s also important to watch how load is distributed across the week: do you have clear hard/easy days, or is every day more or less the same?
Sports scientist Carl Foster’s Training Monotony and Training Strain are useful indicators for reviewing load distribution and accumulated strain.
Example card: values are for UI preview only. Interpret using your own data and trends.
1. Training Monotony
What is monotony?
Training monotony reflects the day-to-day variability of your training load.
- Low monotony: clear hard/easy separation—hard intervals one day, easy run next, then rest.
- High monotony: nearly the same load every day (for example, running 10 km at the same pace daily). This pattern can make fatigue harder to dissipate and may contribute to stagnation.
Formula
Monotony is typically computed over one week:
Monotony = mean(daily_load) / stdev(daily_load)Note: some platforms use modified formulas (e.g. mean / (stdev + mean)) to avoid infinities when stdev is 0, but the classic Foster formula is widely used.
Interpretation
| Monotony | Rating | Guidance |
|---|---|---|
| < 1.5 | Variable | Reasonable day-to-day variation; recovery days are likely visible. |
| 1.5 - 2.0 | Watch | Training is becoming more uniform; review hard/easy separation. |
| > 2.0 | High monotony | Daily load is very similar. Consider adding clearer rest, easy, and hard days. |
Key principle: improvement usually needs contrast. Hard days and easy days should be meaningfully different, not blurred into the same medium effort every day.
2. Training Strain
What is training strain?
Training strain combines total load and monotony into one metric. It estimates how demanding a training week may be when both volume and day-to-day similarity are considered.
This explains why a week with modest total TSS can still feel crushing if it is highly monotone.
Formula
TrainingStrain = TotalWeeklyLoad * Monotony
= sum(load) * (mean(load) / stdev(load))Practical use
- Don’t look at TSS only: two weeks can both be 500 TSS, but if one has monotony 1.2 (strain 600) and the other 2.5 (strain 1250), the second is far more taxing.
- Monitor overload blocks: during overload weeks, total load rises. Make sure monotony stays controlled (rest days must be real rest), otherwise strain can spike dramatically.
How Trainingload.ai uses monotony
Trainingload.ai uses monotony to review the structure of a week, not only its total load. If weekly TSS is reasonable but monotony is high, the plan may still need clearer easy days, rest days, or better separation between key sessions.
This is especially useful when an athlete reports “always tired” despite moderate load. The problem may not be total volume; it may be that every day looks too similar.
Summary
In a PMC view, don’t watch CTL only. Regularly check Monotony and Strain:
- Add variation: include at least 1–2 full rest days or very easy recovery days each week.
- Avoid “same every day”: don’t run the same distance at the same pace daily.
- Be cautious with high values: if monotony stays > 2.0 for a long time, review recovery and day-to-day variation even if total load looks moderate.
References
- Fellrnr: Training Monotony
- Foster C. Monitoring training in athletes with reference to overtraining syndrome. Med Sci Sports Exerc. 1998.
Acute:Chronic Workload Ratio (ACWR)
ACWR compares recent load with longer-term baseline load to flag unusually fast training-load increases.
Aerobic Capacity
Aerobic capacity describes the upper range of oxygen use during hard efforts, commonly represented by VO2 Max and interpreted alongside thresholds, economy, and training load.