School’s Out — The XYZs of Cycling

As a follow-up to our “A.B.C. - Always Be Cycling / Cracking the Codes of Modern Cycling” blog, we’re continuing our exploration of the cycling lexicon. School might be out for the summer, but we can keep the wheels of education turning as we dive into more terms and metrics that appear on our ever-advancing cycling computers, the wide range of popular training platforms, and in articles on cycling performance. We’ve done our best to break these terms down into their simplest form and an easy-to-understand description, so the next time you overhear someone on the cafe ride discussing “zones, critical power, VAM, or FatMax,” you’ll be able to jump right in, or at least not feel like you’re listening to a foreign language.

Power Zones

We touched on “zones” in our A.B.C. blog, as they relate to a rider’s FTP, but we’ll dig a bit deeper into what each zone means. We’ll be using the widely adopted 7-Zone framework for our breakdown, which is based on the research of Dr. Andrew Coggan. Cycling power zones are used to categorize your riding intensity based on percentages of your Functional Threshold Power (FTP)—the maximum power you can theoretically sustain for one hour. By tracking power, you can target specific energy systems, optimize recovery, and train more effectively than by relying on heart rate or perceived exertion alone.

Zone 1 - Active Recovery (< 55% of FTP)

Feel: Very light, easy spinning. You can easily hold a full conversation.
Purpose: Increases blood flow to tired muscles to clear fatigue after hard rides or races.

Zone 2 - Endurance (56% – 75% of FTP)

Feel: Steady and comfortable. You can maintain this for hours.
Purpose: Builds aerobic base, increases fat oxidation (fat-burning), and boosts mitochondrial density in the muscles. This should make up the bulk (around 80%) of your overall riding volume.

Zone 3 - Tempo (76% – 90% of FTP)

Feel: Moderate to moderately hard. Requires more focus than Endurance, but not an all-out effort.
Purpose: Teaches your body to utilize glycogen stores more efficiently and builds fatigue resistance for long events.

Zone 4 - Threshold (91% – 105% of FTP)

Feel: Hard and uncomfortable. This zone hovers exactly around your FTP.
Purpose: Increases your lactate threshold, allowing you to ride faster for longer before fatigue sets in.

Zone 5 - VO2 Max (106% – 120% of FTP)

Feel: Very hard to extremely difficult. You will be breathing heavily and can sustain it for only a few minutes.
Purpose: Expands your maximum aerobic capacity (the ceiling of your fitness) and increases stroke volume, aka the amount of blood pumped by the heart in one beat.

Zone 6 - Anaerobic Capacity (121% – 150% of FTP)

Feel: All-out effort. You will push to the point of heavy muscular and respiratory fatigue.
Purpose: Develops short-term explosive power, such as attacking a steep hill, an all-out start, or a sprint finish.

Zone 7 - Neuromuscular Power (> 150% of FTP)

Feel: Maximal/Sprint. Complete maximum exertion for short bursts (5 - 15 seconds).
Purpose: Trains the central nervous system and fast-twitch muscle fibres for peak sprint speed.

Critical Power

Critical Power (CP) is the boundary between sustainable and unsustainable effort in cycling. Stay below your CP, and your body can ride comfortably. Push above it, and you will quickly tire out.

The Science of Critical Power

• The Threshold: CP is the highest level of effort your body can maintain, at which energy supply and demand are perfectly balanced. Lactic acid, which is a byproduct of muscle use, is cleared by the body just as fast as it is made.
  
• The Time Limit: Most cyclists can only ride at their exact CP for about 30 to 40 minutes. If you can ride at this power for a full hour, your CP estimate is likely too low.
  
• How it’s Measured: CP is calculated using a series of maximal effort tests (e.g., a 3-minute and a 12-minute test). These results plot on a curve to show exactly how your body handles effort over time.

Critical Power vs. FTP

Many cyclists confuse Critical Power with Functional Threshold Power (FTP). Both are estimates of your physical limits, but they have key differences:

• FTP is defined as the maximum power you can hold for exactly one hour.
• CP is based on shorter, multi-duration tests that analyze your overall energy systems, making it more scientifically accurate for modern training.
• CP is usually about 3% to 8% higher than FTP.

The W’ (W-Prime) Factor

When you push power above your CP, your body relies on a finite reserve of anaerobic energy called W’ (W-Prime).

• Think of W’ like a backup battery.
• Every second you pedal above CP, you drain your W’ battery.
• Go slightly over CP, and the battery drains slowly. Sprint hard over CP, and the battery empties fast.
• Once your W’ battery is totally drained, you have to slow down below CP to recover.

Knowing your CP and W’ helps you pace races, attack climbs without blowing up, and plan your training zones.

VAM

VAM stands for velocità ascensionale media in Italian, or “average ascent speed” in English. It measures the number of vertical metres you climb per hour, such as 800 metres per hour (m/h) to show how fast you climb.

The formula for VAM:

  Vertical meters climbed × 60

  Time taken in minutes

Think of VAM like a vertical speedometer. If you climb 300 vertical metres in 20 minutes, your VAM is 300m × 60 / 20 minutes = 900m/h. This means that if you kept climbing at that exact same speed for one hour, you would gain 900 vertical metres.

VAM Benchmarks

Professional cyclists have very high VAM scores. Here are some general standards:

• Grand Tour Winners: 1,650 to 1,800 m/h
• Advanced Amateurs: 1,000 to 1,300 m/h
• Average Club Cyclists: 700 to 900 m/h

Why Cyclists Use VAM

• No Power Meter Needed: VAM only requires your ride time and the elevation change. That being said, it’s great insight to see what power output was required to achieve a specific VAM value on a given ascent.
• Compare Different Climbs: Use VAM to compare how well you climb on different hills. If you ride different hills at the same grade (e.g., 8% slope), your VAM lets you know if you are getting faster or slower.
• Pro cycling teams will often use VAM to gauge the efforts of their opponents, as an alternative to power data, which they can’t access. It helps directors and coaches estimate a rival’s power, predict fatigue, and decide whether to attack or defend.

Limitations

VAM varies with the steepness of the hill. On a very flat 2% grade, you must ride incredibly fast horizontally to gain vertical height, which adds wind resistance. On a 10% grade, you ride much slower to gain the same vertical height. As a result, it is best to compare VAM scores on hills with similar gradients.

FatMax

FatMax is a term that refers to the specific cycling intensity where your body burns the most fat for fuel. It typically happens at a moderate pace, often in Zone 2. Training at this intensity forces your body to become more efficient at using stored body fat for energy. This saves your limited carbohydrate stores for harder efforts.

Why is FatMax important?

• Saves Carbs: Your body only stores a small amount of carbohydrates (glycogen), while it has a nearly unlimited supply of fat.
  
• Prevents “Bonking”: Using fat for energy delays the dreaded feeling of running out of fuel.
  
• Better Pacing: It helps you ride longer without needing to eat as much on the bike.

Where is FatMax?

FatMax is an intensity, not a specific speed. For most cyclists, it occurs around 60% to 75% of your FTP or maximum heart rate. A simple real-world test for FatMax is a pace where you can still hold a normal conversation without gasping for air.

How to Find Your FatMax

• Lab Testing: Professionals measure your breathing and oxygen use while you ride on an indoor trainer.
• Field Test: You can use a power meter and heart rate monitor. You ride for 20 to 45 minutes, slowly increasing your power to track when fat burning peaks.
• One reason pro cyclists spend countless hours training in Zone 2 is to increase their FatMax. The higher it is, the more their bodies are able to utilize fat stores and save other forms of energy for when the intensity spikes at key points in a race. This ability may be equally or more important than one’s FTP value in the pro peloton, as further FTP gains are harder to achieve at that level.

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