TL;DR
🔹 Your Training Load is the cumulative amount of stress you experience from your workouts
🔹 It’s personal, based on your completed workouts, and charts your Chronic Training Load (CTL), Acute Training Load (ATL) and the Training Stress Balance (TSB) between them
🔹 Your Training Stress Score (TSS) or Running Stress Score (RSS) are numbers calculated for each workout based on the intensity and duration of the workout
🔹 Your Chronic Training Load (CTL) models historical training load to which you may have adapted
🔹 Your Acute Training Load (ATL) models recent training load to which you haven’t yet adapted
🔹 Your Training Stress Balance (TSB) is your CTL minus your ATL – a positive TSB indicates “freshness”, while negative TSBs indicate “optimal” training balance or “risk of overload”.
🔹 Your Ramp Rate is a measure of the speed with which your CTL changes – ramping too quickly could lead to injury, illness or overtraining.
Questions about your Training Load? Ask them in the from1runner2another Facebook group.
What is your Training Load?
Workouts provide a stimulus for your body to adapt. They also create fatigue.
Your Training Load charts the longer-term improvements from your training against the shorter-term impacts, showing the balance between the two.
Some charts are able to show these metrics for planned workouts too, enabling better management of future training load.
What is TSS? What is RSS?
Training Stress Score (TSS) and Running Stress Score (RSS) are numbers calculated for each workout based on the intensity and the duration of the workout.
Stress scores are relative to CP/FTP, with a Stress Score of 100 representing a 1-hour workout at CP/FTP.
RSS is calculated differently than TSS, but both are calculated using the same principle – that harder or longer activities lead to higher stress scores.
What is my CTL?
Your Chronic Training Load (CTL) models your performance potential – your longer-term accumulated training load to which you may have adapted.
CTL is modelled as an “exponentially-weighted moving average with a 42-day time constant” and takes into account the last 3 months of workouts – more recent workouts contributing more than older workouts.
As you get fitter, you’re able to run harder or longer – it’s not unusual to see CTL improvements continuing for months at a time.
What is my ATL?
Your Acute Training Load (ATL) models your more recent accumulated training load to which you haven’t yet adapted.
ATL is modelled as an “exponentially-weighted moving average with a 7-day time constant” and takes into account the last 2 weeks of workouts – more recent workouts contributing more than older workouts.
As you get fitter, you’re able to run harder or longer and recover more quickly – it’s not unusual to see ATL peaks and troughs, with the overall shape of the line matching changes in CTL.
Why is TSS relative to FTP?
TSS is a single number that needs to work for athletes of varying abilities, producing a score that takes into account both intensity and duration.
Another number that combines intensity and duration for athletes of varying abilities is FTP.
The TSS calculation produces a score of 100 for a 1-hour workout at FTP – it’s relative to athlete-specific FTP numbers.
Why use exponential weighting?
CTL, ATL and TSB are based on the TRIMP impulse-response model commonly used to predict training-induced changes in performance.
Using exponentially weighted moving averages simplifies the original model (a modification proposed by Andrew Coggan PhD).
Exponential weighting reduces the TSS score of older workouts before averaging the adjusted scores – shorter time constants reduce the TSS scores more quickly.
What is my TSB?
Your Training Stress Balance is your CTL (the longer-term improvements) minus your ATL (the shorter-term impacts).
A positive TSB (CTL higher than ATL) indicates “freshness”, with higher values indicating “loss of fitness”.
A negative TSB (ATL higher than CTL) indicates “optimal” training load, with lower values indicating “risk of overtraining”.
Your TSB indicates your ability to express your performance potential (CTL).
It can also be used to plan upcoming workouts (reducing risk of overload) or to plan a taper (to be fresh & ready to go).
What is my Ramp Rate?
Ramp Rate is a measure of the speed with which your CTL changes.
It’s used to assess whether your training is progressing at an appropriate pace – ramping too quickly could lead to injury, illness or overtraining.
Why is it so complicated?
Why CTL, ATL and TSB, rather than fitness, fatigue and form?
CTL, ATL and TSB are not absolute measures of fitness, fatigue or form:
- they simplify the original impulse-response model
- they produce results that are relative indicators of changes in performance
Labelling these metrics fitness, fatigue and form is misleading – CTL, ATL and TSB need to be interpreted within the context of your overall environment (including sleep, other stressors, your diet, other exercise etc.)
How does TSB work for multi-sports?
It’s not designed to!
TSB is based on CTL and ATL, which are based on TSS calculations that are relative to FTP – both TSS and FTP are based on power readings specific to individual sports and power meters.
Multi-sport athletes should maintain training load metrics per sport, and should interpret the sport-specific numbers based on experience.
Where can I see my Training Load?
Training Peaks
- Mobile and Online Apps have a Performance Chart for Premium subscribers
- Chart shows CTL, ATL and TSB for the previous 90 and the next 21 days (if using planned workouts)
- Performance Chart does not show Ramp Rate
- Workouts are automatically synced to TP
WKO
- Paid PC-based software from Training Peaks
- TP accounts are free (optional subscriptions too)
- Can chart CTL, ATL, TSB and Ramp Rate for any previous or future time period
- Workouts can be automatically synced via TP
Stryd Mobile / Power Center
- Free to anyone with a Stryd account.
- Stryd accounts are free (optional subscriptions too)
- Mobile App and Power Center show a Running Stress Balance based on RSS
- Mobile app shows averages (unclear if weighted)
- Neither shows CTL, ATL or Ramp Rate
- Workouts are automatically synced via Power Center
Download pictures as a PDF
The pictures above are available as a downloadable PDF
Feedback? Questions?
If you have questions or recommendations – things that have worked for you – come and share them with us!
Join the discussion in the from1runner2another Facebook group.
For an in-depth article on these concepts from Dr. Coggan, please see “The Science of the Performance Manager“.
