Why Measuring Critical Power and W' Matters: The Key to Unlocking Cycling Performance

Let’s talk about one of the most buzzworthy metrics in cycling right now: Critical Power (CP). No, it’s not just a fancy term your coach throws around to sound scientific – this metric, alongside its trusty sidekick W’ (W Prime), is your go-to duo for unlocking more efficient, effective training. But what are they, why do they matter and what exactly makes them so much more useful than the traditional FTP (Functional Threshold Power)?

Settle in and let’s get technical – but in a way that won’t have you snoozing at the handlebars.

The Power of Critical Power (CP): Beyond FTP

First off, let’s clear up why Critical Power is taking over the cycling world. For ages, FTP (Functional Threshold Power) has been the king of cycling metrics, aiming to give you an idea of how much power you can hold for an hour without completely self-destructing. FTP has its uses, sure, but it’s limited. Imagine trying to sum up an entire athlete’s endurance potential with just one snapshot of an hour – it’s a bit like guessing the depth of the ocean by looking at a puddle.

Enter Critical Power. CP offers a fuller picture, capturing the highest power output you can sustain over time without falling into “energy debt.” It’s a more dynamic, adaptable metric that represents your “power ceiling”. Think of CP as the sustainable pace you can maintain over a longer period, a pace where you’re in the red zone but not about to crash and burn. It’s personalised to each rider’s unique abilities and because it’s based on a range of max efforts (rather than just one static number), it adapts as you get stronger, fitter and more endurant.

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W’ (W Prime): The Secret Anaerobic Reserve

Now, CP doesn’t work alone – it’s got W’. While CP is your “ceiling,” W’ is like the emergency energy stash you pull from when you need to surge past your limit. Think of it as your “anaerobic battery.” When you’re hammering away above CP, you’re draining this battery. It’s finite and once it’s empty, well, that’s when the legs start to scream, the watts plummet and you’re forced to back off.

The magic of W’ is that it’s refillable. Once you drop below CP, your anaerobic capacity starts to recharge. So, you can think of W’ as the secret sauce that lets you make those short, explosive moves, while CP is the limiter that helps you keep a steady, race-winning pace.

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Why CP and W’ are Superior to FTP

While FTP serves as a general marker of fitness, CP and W’ provide a level of precision that’s hard to beat. For example, FTP doesn’t account for those short bursts of energy you’ll need in real-life race scenarios – sprints, climbs, surges. CP and W’ give you both your sustained threshold and the power reserve for explosive moments.

Why Vekta Uses CP and W’ Over FTP:

1. Mathematical Rigor: CP is grounded in a model that considers multiple max efforts, making it more representative of both aerobic and anaerobic systems.
2. Real-Time Adaptation: Vekta continuously updates your CP and W’ with every ride, making it an evolving benchmark that reflects your current state.
3. Greater Practicality: CP and W’ fit the demands of competitive cycling better, where you’ll need both sustained power and burst capacity.

Breaking Down Vekta’s Cycling Power Profile

With Vekta, you get access to our Cycling Power Profile, a feature that turns your data into actionable insights. After each session, our algorithm pinpoints your peak outputs across different intervals, giving you a complete power profile. Here’s what each key duration tells you:

1. 5 Seconds: Max sprint power and your explosive strength.
2. 1 Minute: Your anaerobic capacity for short, intense surges.
3. 5 Minutes: Estimated VO2 max – your power for sustained efforts.
4. 20 Minutes: Reflects your longer-duration power output.
5. 1 Hour: This one’s all about your endurance and staying power.

Vekta’s real-time updates ensure that your profile keeps pace with your progress. No more static numbers or outdated stats – every ride, every effort, feeds into an adaptive, living profile that represents you.

How to Measure and Improve CP and W’

Curious to find out your CP and W’? Here’s a quick test you can try. Just bring your best effort, an open road and maybe a stiff drink for after.

Classic CP Test Protocol:

1. 15-Second Max Sprint: Go full gas to measure peak anaerobic power.
2. 3-Minute Max Effort: This gives a measure of short-term, high-power capacity.
3. 12-Minute Max Effort: The final nail in the coffin, this sustained effort completes your CP calculation.

Want to make this easier? Vekta’s algorithm adapts and auto-updates based on your sessions, so there’s no need for a formal test every few weeks. Just go out, do your thing and let the AI handle the heavy lifting.

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Real-World Benefits of CP and W’ for Training

So, what does all this mean in the real world? Let’s break down how CP and W’ can benefit your training:

1. Training Precision: CP allows for intensity prescriptions that are just right – not too easy, not too brutal. Coaches can target the perfect intensity for adaptation without pushing athletes into burnout territory.
2. Fatigue Management: Knowing your CP helps balance work and rest. With Vekta’s data, both you and your coach can see if you’re pushing too hard or leaving gains on the table.
3. Tactical Race Insights: W’ tells you how long you can maintain a high effort before your anaerobic tank runs dry. Ideal for planning when to attack or hold back.

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Using CP and W’ to Customise Your Training

With Vekta’s Adaptive Training Zones, you can set training zones based on your CP and W’. Each zone serves a specific purpose and maximises your time spent at each intensity level:

1. Endurance Zone: For building a rock-solid base.
2. Aerobic Zone: Improves aerobic energy efficiency and capacity.
3. Threshold Zone: Pushing this zone increases your CP, essentially raising the “ceiling” of your power.
4. VO2 Max Zone: Taps into maximum oxygen uptake, crucial for those high-intensity moments.
5. Anaerobic Zone: Explosive power – for sprints, hill attacks and short accelerations.
6. Neuromuscular Zone: The peak of the peak, where you develop the highest level of force.

Each workout is customised to your exact profile, adapting as your CP and W’ change, ensuring your training is always optimised for results.

Visual Guide to CP and W’

To make this crystal clear, imagine a power bar:

• CP is the threshold line across the bar, marking your “sustainable power ceiling.”
• W’ is the fillable part of the bar above that line – this is your anaerobic capacity. When you’re sprinting, this section depletes, but it starts filling up again as soon as you back off.

When used effectively, this model lets you see exactly how much effort you’ve got left in the tank, ideal for planning those last race kilometres or deciding if you can power through a climb.

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Why Vekta’s Dynamic Tracking Matters

Most apps give you a static power estimate, but Vekta’s dynamic model adapts as you do. Using advanced CP modelling and recent max-effort data, Vekta keeps your metrics relevant, reflecting your current performance level rather than something from last month.

For athletes, this means no more outdated training data. For coaches, it’s an immediate view of where an athlete stands, so they can adjust workouts with laser precision.

Real-World Example: How Zack Uses CP and W’ for Training Success

Take Zack, a triathlete who loves hills but struggles with those relentless flats. After using Vekta’s CP and W’ analysis, he and his coach discovered her W’ was draining too quickly during extended surges. By focusing on targeted W’ workouts (like short, repeated sprints), Zack increased his capacity to handle prolonged, high-intensity efforts.

Next race, Zack held her power steady, even on the longest flats, thanks to her improved W’. His coach, meanwhile, could see exactly when he was ready to push harder without risking burnout.

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Why CP and W’ Matter for Every Cyclist

Whether you’re a coach, a racer, or a weekend warrior, CP and W’ are the real game-changers. By understanding your power limits and anaerobic reserve, you’re no longer just riding on feel. You’re training with science on your side.

And the best part? Vekta’s adaptive power profile means you’re always working with the most accurate, up-to-date numbers. So, when you’re ready to level up, Vekta’s right there with you.

Ready to get started with Vekta’s CP and W’? Head to our subscription page and find out how our insights can help you ride smarter, stronger and better.

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