Training Peaks Metrics

This article covers all the metrics in TrainingPeaks and how they are calculated.

Metric	Explanation	Calculation
TSS - Training Stress Score	A composite score estimating the training load of a workout based on intensity and duration.	TSS = (Duration (s) x NP x IF) / (FTP x 3600) x 100
IF - Intensity Factor	A measure of workout intensity relative to your Functional Threshold (FTP/CP/LT).	IF = NP / FTP
NP - Normalized Power	An adjusted power value that accounts for variability in effort, better reflecting physiological cost than average power.	Calculated by smoothing power with a 30s rolling average, raising to the 4th power, averaging, then taking the 4th root.
EF - Efficiency Factor	The ratio of Normalized Power (or Pace) to Heart Rate; used to track aerobic efficiency.	EF = NP (or Normalized Graded Pace) / Average HR
VI - Variability Index	A measure of pacing smoothness: NP divided by average power. Values >1.05 suggest inconsistent pacing.	VI = NP / Average Power
CTL - Chronic Training Load	The rolling average of daily TSS over ~42 days, representing long-term fitness.	CTL = exponentially weighted average of daily TSS over 42 days
ATL - Acute Training Load	The rolling average of daily TSS over ~7 days, representing short-term fatigue.	ATL = exponentially weighted average of daily TSS over 7 days
TSB - Training Stress Balance	The difference between CTL and ATL; positive values suggest freshness, negative values indicate fatigue.	TSB = CTL - ATL
Pw:Hr - Power-to-Heart Rate Decoupling	The percentage drift between power (or pace) and heart rate over steady-state efforts; indicates aerobic durability.	Pw:Hr = (Power:HR ratio in 2nd half / ratio in 1st half - 1) x 100
w'bal - Work Capacity Balance	Tracks remaining anaerobic work capacity during an effort, based on critical power modeling.	Calculated using critical power model: W'bal = W' - ∑ (work above CP - recovery below CP)
rTSS - Running TSS	Running-specific TSS based on pace, heart rate, or power, accounting for intensity and duration.	rTSS = (Duration x IF2 x 100) / (Reference pace/power threshold)
sTSS - Swim TSS	Swimming-specific TSS, often derived from pace and threshold pace.	sTSS = (Duration √ó IF2 x 100) / (Threshold swim pace)
FTP - Functional Threshold Power	The highest average power an athlete can sustain for ~1 hour; used to scale power zones.	Estimated via 60-min test, or commonly 95% of 20-min best effort.
LTHR - Lactate Threshold Heart Rate	The highest heart rate an athlete can sustain for ~1 hour; used to set HR training zones.	Determined from race data or field testing (e.g., 30-60 min TT).