Cycling training terms,
explained plainly.
Every term here is something you’ll meet inside AdaptCycling — or anywhere power-based training gets discussed. Short definitions, the math where it matters, and how we use each term in the product.
FTP (Functional Threshold Power)
The highest average power you can sustain for approximately one hour. Used to anchor every training zone and workout prescription.
TSS (Training Stress Score)
A single-ride training-load score that combines duration and intensity. One hour at FTP equals 100 TSS. Used to sum daily and weekly training load.
CTL (Chronic Training Load)
A 42-day exponentially-weighted average of daily TSS — the fitness side of the fitness/fatigue model. Rising CTL means you're accumulating fitness.
ATL (Acute Training Load)
A 7-day exponentially-weighted average of daily TSS — the fatigue side. ATL responds fast; it's why you feel flat after a hard block.
TSB (Training Stress Balance)
CTL minus ATL — your 'form.' Negative TSB means freshness-in-debt (high fatigue); positive TSB means you're rested and primed for a race.
Intensity Factor (IF)
A ride's normalized power divided by your FTP. IF around 0.90 is a typical sweet-spot effort; IF 1.00 is an hour at FTP.
Normalized Power (NP)
A power metric weighted to reflect the physiological cost of variable efforts. A surgy crit can have NP well above average power.
Sweet Spot training
Sustained efforts at roughly 88–94% of FTP. Produces most of the aerobic adaptations of threshold work with less fatigue — hence 'sweet spot.'
Polarized training
Distribution where ~80% of training is easy (below the first threshold) and ~20% is genuinely hard (threshold-to-VO2max), with little in the moderate middle. Popularized by Seiler.
VO2max
Maximum rate your body uses oxygen during exercise. Trainable via short intervals (3–8 min) near maximum sustainable aerobic output.
Critical Power (CP)
The highest power sustainable in a metabolic steady state — the asymptote of your power-duration curve. A close physiological cousin of FTP.
W' (anaerobic work capacity)
Your finite work capacity above Critical Power, in kilojoules — the 'battery' you drain on hard efforts and recharge when you ease below CP.
Power curve (mean maximal power)
Your mean maximal power for every duration. Its shape reveals rider type and lets us estimate FTP, CP, and W' without a formal test.
Lactate threshold (LT1 & LT2)
The intensities where blood-lactate behavior shifts — LT1 (aerobic, ~2 mmol/L) and LT2 (anaerobic / MLSS, ~4 mmol/L). FTP is the field proxy for LT2.
Zone 2 (aerobic endurance)
Low-intensity aerobic endurance, roughly 56–75% of FTP and below the first threshold. Conversational riding that builds the aerobic base.
Tempo (Zone 3)
Moderate riding at ~76–90% of FTP — 'sustainable but working.' Useful in doses, but the classic grey-zone trap when it becomes your default.
Aerobic decoupling (cardiac drift)
Cardiac drift: heart rate climbing relative to power over a long steady effort. Above ~5% (Pw:HR) it flags an aerobic-base or durability limit.
Durability (fatigue resistance)
Resistance to the late-ride decline in power and efficiency after hours of work — endurance's emerging 'fourth dimension' beyond VO2max.
Ramp rate (CTL ramp)
How fast your CTL climbs per week. A sustainable band is roughly 3–8 CTL/week; hold it higher for too long and you risk overreaching.
Periodization
Structuring training into phases — base, build, peak, taper — across macro, meso, and microcycles to progress toward a goal event.
Taper
Progressive pre-event load reduction — cut volume ~40–60%, hold intensity — to shed fatigue while preserving fitness. Worth ~2–3%.
Relative Effort (Strava)
Strava's HR-based training-load score, successor to the Suffer Score. Because it's heart-rate-based, it's not comparable to power-based TSS.