Athlete summary
Your Performance Management Chart already shows fitness (CTL), fatigue (ATL), and form (TSB). Those tell you whether you are fresh or cooked today.
Two extra overload guards watch how the week is shaped:
| Signal | Question it answers |
|---|---|
| Foster monotony | Are daily loads too similar? (flat weeks without recovery contrast) |
| Foster strain | How hard is that flat week in absolute terms? (monotony × weekly load) |
| CTL Δ/week | How fast is fitness climbing vs seven days ago? |
TSB remains the primary form number. Monotony / strain / CTL ramp are additional adaptive signals — they can propose easing quality days even when TSB is not yet deeply negative.
Formulas (engine)
Over a trailing 7 calendar days (rest days counted as 0 load):
mean = average(daily_load)
SD = population standard deviation(daily_load)
monotony = mean / SD # undefined when SD ≈ 0
strain = monotony × Σ(daily_load)
ctl_delta_week = CTL_today − CTL_(today−7)Load is the same daily series as the PMC (TSS, or hrTSS/TRIMP in HR-only mode).
Guardrail thresholds
| Guard | Caution | Notes |
|---|---|---|
| Monotony | ≥ 2.0 | Foster 1998 — elevated illness / overreaching risk when sustained |
| Strain | ≥ 2.0 × weekly load | Scaled — a 500 TSS week needs strain ≥ 1000 (not a fixed 600) |
| CTL Δ/week | ≥ +5 caution, ≥ +8 hard | Coaching convention on Coggan PMC ramp rate |
Because strain = monotony × weekly_load, the scaled strain cutoff is exactly the strain implied by monotony at 2.0 for this week's volume. Well-varied high-TSS weeks stay below it; flat monotonous weeks cross it.
Foster metrics require a full contiguous 7-day calendar window ending on the decision day (rest days as 0). Shorter history leaves monotony/strain unset so a handful of similar early rides cannot inflate adaptive guards; CTL Δ/week still reports when both endpoints exist.
When elevated, adaptive coaching can enqueue inbox proposals that downgrade hard roles (same easing path as fatigued TSB), with citations for monotony, strain, and ctl_delta_week.
Literature
- Foster, C. (1998). Monitoring training in athletes with reference to overtraining syndrome. Medicine & Science in Sports & Exercise.
- Coggan — Performance Manager / CTL–ATL–TSB (TrainingPeaks and successors) for the CTL week-ramp definition used alongside Foster.