FT – Functional Threshold power. The mean maximal power over one hour.

Pn (normalized power) - an estimate of the power that you could have maintained for the same physiological "cost" if your power output had been perfectly constant (e.g., as on a stationary cycle ergometer), rather than variable.

IF – Intensity Factor
IF = Pn/FT. The ratio of the normalized power as described above to your threshold power.

TSS – Training Stress Score
TSS = IF x IF x duration in hours x 100. Takes into account both the intensity (i.e., IF) and the duration of each training session.

CTL – Chronic Training Load. CTL is an exponentially weighted average of TSS per day with a 42 day Time Constant (TC). Or in other words it takes into account mostly the last six weeks of training. CTL can be thought of as “fitness”.

CTL= CTLy + (TSS-CTLy)/TC

CTLy = yesterdays CTL
TC = Time constant

ATL – Acute Training Load. ATL is an exponentially weighted average of TSS per day with a 5-10 day Time Constant (TC). Or in other words it takes into account mostly the last 5-10 days of training. ATL can be thought of as “freshness”

ATL= ATLy + (TSS-ATLy)/TC

ATLy = yesterdays ATL
TC = Time constant

TSB - Training Stress Balance. TSB can be thought of as “form”. When you are really fit (high CTL) and really fresh (low ATL), TSB will be high. This is peak form and a desirable score to have on “A” race day.

TSB = CTL – ATL

KPI's - Key Performance Indicators. Resting heart rate, body weight, power output, general feeling of wellness, sleep patterns, appetite. Most athletes hone in on 1 - 2 specific KPI's and record them over time.

PMC - Performance Manager Chart

If you have any training questions, please ask them on my forum