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Power and FTP

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DefinitionA short reference note, not a full lesson.
Definition

Power (watts) is the most objective cardio intensity metric — instant, terrain-immune — and FTP is the threshold anchor its zones are built on.

Detail

Power measured in watts is the external mechanical output, captured by a cycling power meter, a smart trainer, a rower's monitor, or a running power device. Unlike pace (confounded by terrain/wind) and HR (laggy and drifting), power is immediate and terrain-immune, making it the gold-standard intensity signal where a meter is available.

FTP (Functional Threshold Power) is the highest power roughly sustainable for ~1 hour — a practical proxy for the lactate/critical-power threshold (see Critical Power & Functional Threshold Power (FTP)). It is the anchor for power zones, just as HRmax anchors HR zones. FTP is commonly estimated from a 20-minute test (≈ 95% of 20-min average power) or a ramp test.

Derived power metrics worth logging:

  • Power zones → power-based Time-in-Zone, which avoids HR lag on intervals.
  • Normalized Power (NP) — a weighting that reflects the metabolic cost of variable efforts better than simple average power.
  • W/kg — power-to-weight, the key comparison metric for climbing and racing.
  • Trending FTP over a block is a primary endurance KPI (see KPIs for Endurance); rising power at equal HR is a clean efficiency gain (see Cardio Efficiency (Pace/Power at HR)).

Key facts

  • Power (watts) = external output; immediate and terrain-immune.
  • FTP ≈ max power sustainable ~1 hour; anchors power zones.
  • FTP often estimated as ≈95% of a 20-min test average.
  • Power zones enable lag-free interval time-in-zone.
  • W/kg, Normalized Power, and FTP trend are the key derived metrics.

Connections

Sources

Cited in text — not yet linked
Established power-based-training consensus (Coggan & Allen *Training and Racing with a Power

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Atlas Connections

Critical Power & Functional Threshold Power (FTP)Closely related
FTP is the highest power (watts) you can hold for roughly an hour — a practical field anchor, near the lactate threshold, that all power-based training zones are built from; critical power is its physiological cousin.
Cardio Efficiency (Pace/Power at HR)
Output at a fixed heart rate — faster pace or higher watts for the same HR over time — is the cleanest field signal that aerobic fitness is improving.
Pace, Speed, and Distance
Pace (time per distance) and speed (distance per time) are the same intensity expressed two ways — but raw pace must be read against terrain and conditions.
Logging Heart Rate (Avg / Max)
Average and max HR turn a session into an internal-load measure — how hard your cardiovascular system actually worked, independent of pace.
KPIs for Endurance
Track weekly training volume and intensity distribution as the inputs, and pace-at-HR / FTP / efficiency as the outputs that confirm aerobic fitness is rising.
Time-in-Zone
The minutes you spend in each intensity zone — the metric that verifies whether your easy days were easy and your hard days hard.
What to Log for Cardio
A cardio session is described by duration, distance, pace, heart rate, time-in-zone, power, cadence, elevation, and effort — log what your modality and goal actually use.