When it comes to cycling performance metrics, Functional Threshold Power (FTP) and Critical Power (CP) often come up as tools for understanding and optimising training. While both serve important purposes, they differ significantly in their origins, applications, and the insights they offer. Let’s break this down by tracing the history of these metrics and exploring their differences in a relatable and practical way.

The Origins of FTP

Functional Threshold Power was popularised by Dr. Andrew Coggan as a benchmark for cycling performance. FTP is defined as the maximum power a cyclist can sustain for approximately one hour. It has become a cornerstone of many training plans, serving as the basis for setting training zones and evaluating fitness.

Think of FTP as the "fuel efficiency" indicator in a car. It represents how well you can maintain a steady output over a specific duration. However, FTP is derived from an estimation, often requiring a 20-minute test with adjustments, and it assumes a consistent relationship between effort and duration.

Limitations of FTP

Fixed duration dependency
FTP is tied to a one-hour effort, which may not represent performance across shorter or longer durations.

Simplistic estimation
The 20-minute test used to calculate FTP involves adjustments that may not fully account for individual variability.

Limited insight into energy systems
FTP does not provide detailed information about the balance between aerobic and anaerobic contributions.

As a result, FTP is best understood as a practical field estimate rather than a physiologically defined threshold, and it lacks the mechanistic validation seen in Critical Power based models (Poole et al., 2016).

These limitations help explain why alternative models, such as Critical Power, have gained traction where greater physiological precision and pacing insight are required.

Strengths of FTP

Simplicity
FTP provides a straightforward reference point that is easy to test, communicate, and apply.

Widespread adoption
FTP underpins many existing training plans, platforms, and coaching workflows.

Practical utility
FTP offers a consistent anchor for setting training zones, guiding steady-state endurance work, and structuring day-to-day training decisions.

The Origins of Critical Power

Critical Power emerged from exercise physiology research as a measure of sustainable performance (Poole et al., 2016; Vanhatalo et al., 2011).

In theory, CP represents the maximum power output a cyclist can sustain without continual fatigue accumulation.

In practice, CP is derived from multiple time-trial efforts and represents the boundary between aerobic and anaerobic energy systems.

Above Critical Power, time to exhaustion is finite and predictable, commonly occurring within approximately 2–30 minutes depending on the work capacity expended, as consistently observed across repeated laboratory trials (Poole et al., 2016; Vanhatalo et al., 2011).

Using the car analogy, Critical Power is like the "engine power" indicator. It tells you how much consistent performance your engine can deliver without breaking down.

Unlike FTP, which is tied to a fixed duration, CP is more dynamic and reflects your physiological capabilities across various time frames.

This relationship is commonly visualised using a power–duration curve, where Critical Power appears as an asymptote separating sustainable performance from finite work above CP (Poole et al., 2016).

This distinction is not conceptual or theoretical. As described by Poole and colleagues, exercise performed above Critical Power leads to an inevitable loss of physiological steady state, whereas exercise below CP can be sustained with stable metabolic responses (Poole et al., 2016).

Critical Power has been shown to be a physiological fatigue threshold, separating sustainable from non-sustainable exercise, with consistent metabolic stability below CP and predictable exhaustion when work above CP is accumulated (Poole et al., 2016; Jones et al., 2010).

Strengths of Critical Power

Where FTP offers simplicity and accessibility, Critical Power provides deeper physiological insight and greater flexibility across real-world riding conditions.

Dynamic measurement
CP accounts for performance across multiple durations, offering a more nuanced view of capabilities.

Energy system insight
CP reflects the boundary between sustainable and unsustainable efforts, aiding in training precision.

Adaptability
CP is useful for pacing strategies, race simulation, and tailoring training to specific demands.

Key Differences Between FTP and CP

Why Vekta’s Focus on CP Matters

By prioritising Critical Power, Vekta shifts the focus from static benchmarks to dynamic, individualised training.

CP encourages athletes to understand their physical limits and train strategically to improve them.

It’s not just about analysing what happened; it’s about shaping what’s possible.

In Conclusion

Understanding both metrics, and their differences, is key to optimising performance. While FTP offers a standardised view of fitness, Critical Power provides a flexible, adaptable framework for training.

Think of CP as a forward-thinking tool in your cycling toolbox, capable of driving your performance to new heights.

Start your free 14-day trial or book a demo.

References

The following peer-reviewed research underpins the physiological definitions and distinctions discussed in this article.

Poole, D. C., Burnley, M., Vanhatalo, A., Rossiter, H. B., & Jones, A. M. (2016).
Critical power: An important fatigue threshold in exercise physiology.
Medicine & Science in Sports & Exercise, 48(11), 2320–2334.
https://doi.org/10.1249/MSS.0000000000000939

Jones, A. M., Vanhatalo, A., Burnley, M., Morton, R. H., & Poole, D. C. (2010).
Critical power: Implications for determination of VO₂max and exercise tolerance.
Medicine & Science in Sports & Exercise, 42(10), 1876–1890.
https://doi.org/10.1249/MSS.0b013e3181d9cf7f

Vanhatalo, A., Poole, D. C., & Burnley, M. (2011).
Determination of critical power using a 3-min all-out cycling test.
Medicine & Science in Sports & Exercise, 43(3), 548–555.
https://doi.org/10.1249/MSS.0b013e3181f20587