Time Trial (TT) Power Pacing: Why TT Pacing Isn’t FTP × 100%

Many cyclists participating in their first Time Trial (TT) assume, “FTP is your 1-hour power, so a 40K TT takes about 60 minutes—just pace at FTP × 100%.” In practice, almost everyone blows up—the first 20 minutes feel great, but after 30 minutes power drops to just 80% of FTP, and the last 10K becomes a crawl.

TT pacing is far more complex than a single FTP number. This article breaks it down from three angles: physiology, aerodynamics, and pacing strategy.

1. The True Definition and Limitations of FTP

FTP (Functional Threshold Power) is “the maximum average power you can sustain for approximately 60 minutes in a fresh state, in a single effort.” But this definition has two often-overlooked prerequisites:

• Fresh state: Just warmed up, with no accumulated fatigue from prior efforts
• Single maximal effort: Fully committed both mentally and physically

In a TT event, however:

• You may have been standing in the transition area for 20 minutes
• Oxygen uptake efficiency in the TT position is 3–5% lower than on a road bike
• The course has climbs, corners, and headwind sections, making power output uneven

2. Recommended Pacing for Different TT Distances

Key concept: The longer the distance, the further pacing falls below FTP, because anything over 60 minutes inevitably enters the realm of glycogen depletion and rising core body temperature.

3. The Physiological Cost of the TT Position

The aero bar position on a TT bike compresses the abdominal cavity, affecting diaphragm movement:

• Maximal oxygen uptake (VO2max) drops by 2–4%
• Heart rate rises 3–5 bpm at the same power
• Economy decreases (more oxygen consumed for the same output)

This means your “FTP” in the TT position is actually 3–5% lower than the FTP measured on a road bike. Many advanced riders test both “road bike FTP” and “TT bike FTP” separately, using the latter for pacing.

4. Pacing Strategy: Negative Split vs. Average Power

Research shows that a negative split—slightly lower early, slightly higher late—yields the best performance:

• First 1/3: 95% of target power
• Middle 1/3: 100% of target power
• Final 1/3: 102–105% of target power

In practice, however, most riders “go out too hard”—adrenaline plus environmental stimulation makes it easy to surge to target + 30W in the first 5 minutes. Use a power meter to enforce limits: for the first 5 minutes, absolutely do not exceed target + 10W.

5. The Impact of Terrain on Pacing

Variability Index (VI) = Normalized Power / Average Power.

• Flat TT: VI close to 1.00
• Rolling TT: VI of 1.05–1.10 is a reasonable range
• VI > 1.15 indicates pacing is out of control, and a late-race collapse is inevitable

On climbs, you can briefly go 5–10% above FTP; on descents, let power drop naturally but keep cadence up to avoid spinning freely.

6. Conclusion

TT pacing = FTP × distance factor × position factor × terrain factor. Simply applying FTP × 100% is the most common cause of blow-ups for beginners. Use a power meter with a preset target power range, and simulate race intensity in training to find your true “TT pacing.”

Related Reading

• Time Trial Power Pacing: The Science of Power Distribution in a 40K TT
• Predicting FTP from Short-Duration Tests: Accurate Estimation Without Riding a Full Hour
• How to Effectively Improve FTP: From Testing to Practical Training Plans
• A Comprehensive Comparison of FTP Testing Methods: Accuracy and Applicability of the 20-Minute Test vs. the Ramp Test