Calculator inputs
Example data table
| Date | Load | CTL | ATL | TSB | Zone |
|---|---|---|---|---|---|
| 2026-03-25 | 40.00 | 41.95 | 46.00 | -4.05 | Balanced build |
| 2026-03-26 | 55.00 | 42.26 | 47.29 | -5.02 | Balanced build |
| 2026-03-27 | 0.00 | 41.26 | 40.53 | 0.73 | Balanced build |
| 2026-03-28 | 78.00 | 42.13 | 45.88 | -3.75 | Balanced build |
| 2026-03-29 | 92.00 | 43.32 | 52.47 | -9.15 | Balanced build |
| 2026-03-30 | 35.00 | 43.12 | 49.98 | -6.85 | Balanced build |
| 2026-03-31 | 0.00 | 42.09 | 42.84 | -0.74 | Balanced build |
| 2026-04-01 | 110.00 | 43.71 | 52.43 | -8.72 | Balanced build |
This sample shows how repeated hard days can lift ATL faster than CTL, pushing TSB downward until recovery starts to restore freshness.
Formula used
Training Stress Balance (TSB) is commonly modeled from long-term fitness load and short-term fatigue load.
CTL today = CTL yesterday + (Daily Load − CTL yesterday) ÷ CTL time constant
ATL today = ATL yesterday + (Daily Load − ATL yesterday) ÷ ATL time constant
TSB today = CTL today − ATL today
CTL reacts slowly and often uses a longer time constant such as 42 days. ATL reacts faster and often uses a shorter time constant such as 7 days. A negative TSB usually means accumulated fatigue. A positive TSB usually means more freshness.
How to use this calculator
1. Enter a label, start date, and your preferred load unit.
2. Add starting CTL and ATL values if you already track them. Otherwise use reasonable estimates from your recent training history.
3. Paste daily training loads in order. Use zero for full rest days.
4. Adjust CTL and ATL time constants if your coaching model differs.
5. Submit the form to review CTL, ATL, TSB, recovery projections, and the graph. Export the history table as CSV or PDF when needed.
Frequently asked questions
1. What does training stress balance tell me?
It estimates how fresh or fatigued you may be by comparing long-term load against short-term load. It helps guide hard sessions, recovery timing, and taper decisions.
2. Why can my TSB become very negative?
A very negative value usually means recent load rose faster than your long-term fitness load. That can happen during overload blocks, training camps, or back-to-back hard sessions.
3. Is a positive TSB always better?
No. Positive TSB often means higher freshness, but very high positive values may also reflect reduced training. The best target depends on whether you are building fitness, recovering, or racing.
4. What should I use as daily load?
You can use TSS, TRIMP, session load, or another consistent stress metric. The key is staying consistent so day-to-day changes reflect real workload patterns.
5. Why are CTL and ATL time constants adjustable?
Different sports, coaches, and data systems use different assumptions. Adjustable constants let you align the calculator with your monitoring method instead of forcing one model.
6. What is monotony and why does it matter?
Monotony compares the average recent daily load with its variation. High monotony means several days look similarly demanding, which may raise fatigue and recovery risk.
7. Can I use this during a taper?
Yes. Tapers often reduce ATL faster than CTL, which can raise TSB and improve freshness. The graph helps show whether that shift is happening as expected.
8. Does this replace coaching or medical judgment?
No. It is a planning tool. Always compare results with performance, soreness, sleep, illness, heart rate trends, and qualified professional guidance when necessary.