Performance
Training Load Calculator — ATL, CTL & TSB Form Score
Calculate your Acute Training Load (ATL), Chronic Training Load (CTL), and Training Stress Balance (TSB) to identify your current form and optimal race window.
Your average training hours per week over the past 6 weeks
Average perceived effort across all sessions (1 = walk, 10 = max)
Duration (min)
RPE (1–10)
Duration (min)
RPE (1–10)
Duration (min)
RPE (1–10)
Duration (min)
RPE (1–10)
TSB > +15. You are too fresh — fitness is declining. You have likely been resting too long.
Race Readiness
Poor — reduced fitness from insufficient load
Recommendation
Gradually increase training volume over the next 1–2 weeks. Add 10–15% more weekly TSS.
What Is Training Load?
Training load quantifies the physiological stress placed on your body by a workout or training week. It combines duration and intensity into a single number — Training Stress Score (TSS) — which then feeds into three derived metrics:
* ATL (Acute Training Load): Your 7-day rolling training stress. High ATL = high fatigue. * CTL (Chronic Training Load): Your 6-week average daily stress. High CTL = high fitness. * TSB (Training Stress Balance): CTL − ATL. Your form indicator.
The TSB Form Scale
| TSB Range | State | Race Readiness | | :--- | :--- | :--- | | > +15 | Detraining | Poor — fitness declining | | 0 to +15 | Optimal Form | Peak — race window is open | | −10 to 0 | Slightly Fatigued | Good — minor taper needed | | −25 to −10 | Fatigued | Moderate — 7–10 day taper needed | | < −25 | Overreached | Poor — rest is mandatory |
The Periodization Principle
Elite endurance coaches structure training in cycles that deliberately push TSB deeply negative during high-volume blocks, then allow it to recover positively before key races. This is called supercompensation — you must stress the system before rest produces adaptation.
Q: How do I use TSB for race planning? A: Work backwards from your target race date. Identify the final training block (TSB should be around −25 at peak), then plan a 10–14 day taper that brings TSB into the 0 to +10 range by race morning.
Q: My CTL is low. How do I build it? A: Increase weekly volume by no more than 10% per week. CTL responds to consistent moderate load far better than sporadic big training weeks. Consistency beats intensity in aerobic development.
Frequently Asked Questions
What is a good CTL for a marathon runner?
A CTL of 60–80 TSS/day represents a solid recreational marathon base. Elite marathon runners often carry CTLs of 100–120 TSS/day. For your first marathon, aim for a CTL of 50+ by the start of taper.
How long should my taper be?
For a marathon or Ironman, a 2–3 week taper is standard. Reduce weekly volume by 30–40% in week one of taper, 40–50% in week two, and 60–70% in the final pre-race week. Maintain intensity (short race-pace sessions) throughout the taper.
What RPE should I use for easy runs?
Easy runs should be RPE 3–4 on a 10-point scale. You should be able to speak in full sentences without gasping. Easy running is the foundation of aerobic base — it should comprise 75–80% of all training.
Data sources & references
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