Functional Threshold Power (FTP) is the single most useful number in cycling training. It's the power output you can sustain for approximately one hour at maximum steady effort — and it's the reference point from which every training zone is derived. Without it, you're training by feel and guesswork. With it, every session has a precise, physiology-grounded target.
What FTP Actually Measures
FTP represents the highest power output at which lactate production and clearance are roughly balanced — the top of your aerobic steady state. Above FTP, lactate accumulates faster than it can be cleared; performance deteriorates within minutes. Below FTP, you can sustain effort for hours.
This makes FTP the dividing line between sustainable and unsustainable intensities. All structured training zones are defined relative to it.
The Standard FTP Test: 20-Minute Protocol
The most widely used field test:
- Warm-up: 20 minutes easy riding, including 2–3 short (30-second) hard efforts to prime the neuromuscular system
- 5-minute all-out effort: Ride as hard as you can for 5 minutes to clear out any anaerobic "freshness" that would inflate your 20-minute result
- 5-minute easy recovery
- 20-minute all-out effort: Ride at the highest average power you can sustain for exactly 20 minutes. Start slightly conservatively — pacing matters. A blown effort in the first 5 minutes invalidates the test.
- FTP = 95% of your 20-minute average power
The 95% correction accounts for the fact that a 20-minute maximal effort is slightly higher than a true 60-minute sustainable power. If you averaged 240W over 20 minutes, your estimated FTP is 228W.
The Ramp Test: A More Forgiving Alternative
The ramp test, popularised by TrainerRoad, involves progressive 1-minute steps of increasing power until failure. FTP is estimated as 75% of the highest 1-minute power achieved. It's shorter, less pacing-dependent, and more accessible for athletes who struggle with the discipline of the 20-minute protocol.
The ramp test tends to slightly overestimate FTP for riders with strong anaerobic capacity and underestimate for pure diesel aerobic riders. It's a useful starting estimate, particularly for beginners.
The 7 Training Zones Derived From FTP
Once you have your FTP, every training zone follows:
- Zone 1 — Active Recovery: <55% FTP. Easy spinning. Recovery rides only.
- Zone 2 — Endurance: 56–75% FTP. The aerobic base zone. Most training volume should be here.
- Zone 3 — Tempo: 76–90% FTP. Moderately hard. Often overused — requires significant recovery without the strong adaptation signal of Zone 4+.
- Zone 4 — Threshold: 91–105% FTP. The FTP zone. Sustainable for 20–60 minutes. Sweet Spot (88–93%) sits at the upper end of Zone 3 / lower Zone 4.
- Zone 5 — VO2max: 106–120% FTP. Hard intervals. Sustainable for 3–8 minutes per rep. Strong VO2max adaptation signal.
- Zone 6 — Anaerobic Capacity: 121–150% FTP. Very hard, short efforts. 30–120 seconds per rep.
- Zone 7 — Neuromuscular Power: >150% FTP. Sprint efforts. <30 seconds.
How Often to Retest
Retest FTP every 6–8 weeks during a structured training block. After a training camp, fitness surge, or significant rest period, retest before resuming structured sessions — using outdated zones means training at the wrong intensities.
Signs your FTP has increased without a formal test: Zone 4 sessions feel easier than before; you can sustain target power with lower heart rate; your power-to-heart-rate ratio has improved.
Using Your FTP for Training Load Calculations
FTP enables precise Training Stress Score (TSS) calculation for each ride. TSS is how cycling training load is quantified and compared across sessions and weeks. Use the NorthLine Cycling Power Zones Calculator to enter your FTP and instantly generate all seven training zones — then apply them to every session on your training plan.
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