Must-Know Terms for Cyclists
Training with power can feel confusing with all the terms like FTP, TSS, CP, and W’ floating around. What do they actually mean? And more importantly—how do they help you ride stronger?
In this post, I break down the key power training terms in simple language, so you can understand what they are and how to use them in your training. Whether you’re new to power-based cycling or just want a clear explanation, this guide will help you make sense of your data and improve your riding.
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Remember that I share my interpretation, approach and practical use of cycling training concepts using a GPS bike computer.
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This post is part of the Training Concepts series and we use. ideas explained in previous ones. If you have not seen them yet, please do so to get all the benefits of this one.
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Some of the terms used in this post are TrainingPeaks’ trademarks including:
Training Stress Score, Normalized Power, Intensity Factor, Acute Training Load, Chronic Training Load, Training Stress Balance and Efficiency Factor
Cycling with power can feel complicated. But it doesn’t have to be. Today, we’ll break down key power training terms so you can understand and use them in your training.
Anaerobic Threshold
Your anaerobic threshold is the effort level where your body starts producing lactic acid faster than it can clear it. When this happens, your muscles burn, and fatigue sets in quickly.
Anaerobic Capacity
Anaerobic capacity is the total amount of energy your body can produce without using oxygen. This fuels short, high-intensity bursts like sprints or attacking a climb.
It’s limited, though—once it runs out, you must slow down until your body recovers.
VO2max
Your Aerobic Engine. VO2max or Maximal Oxygen Uptake is the maximum amount of oxygen your body can use during intense exercise. It’s a key indicator of your aerobic fitness and endurance potential.
The higher your VO2max, the more oxygen your muscles get, allowing you to sustain high-intensity efforts for longer.
Why it Matters for Cyclists
- Determines endurance potential, a Higher VO2max means better sustained performance.
- Improves aerobic power. More oxygen equals more energy for long rides.
- Essential for high-intensity efforts. Helps with breakaways, climbing, and time trials.
- Foundation for Threshold Power.
Frequency
Frequency is how often you train in a week. More frequent training improves consistency and builds fitness faster.
- Low frequency, 2 or 3 rides per week, usually for maintenance or recovery.
- Moderate frequency, 4 to 5 rides per week, steady progress.
- High frequency, 6 to 7 rides per week, some times more than one session per day, advanced training.
Time or Duration
This is simply how long you ride in one session. Long rides improve endurance, while shorter ones with intervals improve power.
- Short duration, lasting 1 hour or less, great for high-intensity work.
- Medium duration lasting one to 2 hours, balanced mix of endurance and intensity.
- Long duration lasting 3 or more hours, Builds endurance and aerobic base.
Intensity
Intensity is how hard you ride. It’s usually measured by:
Power in watts. The most accurate measure of effort.
Heart rate in beats per minute, useful but can be affected by fatigue, heat, hydration and other factors not related to exercise.
Rate of Perceived effort or RPE
Subjective but very valuable when combined with power. It is a scale used to give a score to the exercise effort from 1 for very easy to 10 for very hard.
Intensity is often controlled using power zones explained later.
Load
Load is the total stress of a workout. It depends on intensity and duration. A short, intense ride and a long, steady ride can both have high load but affect the body differently.
Measured by:
- TSS or Training Stress Score, a number that quantifies the load of a single training session.
- CTL or Chronic Training Load, Long-term training stress over time.
Volume
is the total amount of time you train per week, the combination of frequency and duration.
Increasing volume gradually builds endurance, while too much too soon can cause burnout or injury.
- Low volume: 4 to 6 hours per week
- Medium volume: 7 to 12 hours per week
- High volume: over 12 hours per week
Power
Power is the combination of the force you apply to the pedals, the crank length and your cadence, measured in watts.
It’s the best way to measure effort because it’s instant and doesn’t change based on fatigue or weather, unlike heart rate.
More power at the same effort means you’re getting stronger
Tracking power helps structure workouts and measure progress.
Power Curve
A power curve shows the maximum power you can hold over different time periods—from a few seconds to several hours.
- Short bursts 5 to 10 sec equal to Sprinting ability
- From 1 to 5 minutes equals to Anaerobic power
- 10 to 60 minutes or more equals to aerobic endurance.
Watching your power curve lets you know your anaerobic capacity and helps track improvement over time.
FTP or Functional Threshold Power
FTP is the maximum power you can hold for about an hour without fatiguing. It’s used to set power zones and measure fitness. It is an estimation of your anaerobic threshold.
Higher FTP means stronger aerobic endurance. It improves with structured training.
Functional Reserve Capacity or FRC
It is the total amount of anaerobic energy or anaerobic capacity you have above FTP before you fatigue. Think of it as a battery for hard efforts.
A higher FRC means you can attack and recover faster.
Critical Power or CP
Similar to FTP but calculated differently. It’s the highest power you can sustain for a long time without draining anaerobic energy.
CP and FTP are often close but not exactly the same.
W Prime
Similar to Functional Reserve Capacity, W prime is your anaerobic work capacity, how much hard effort you can do before needing to recover.
Think of it like a fuel tank for short, intense bursts.
Sprinting and attacking drain it, Riding below CP refills it.
Power Training Zones
Power zones help structure training. They are based on FTP and the most commonly used is the 7 zone model:
- Zone 1, Recovery Very easy, helps legs recover.
- Zone 2, Endurance, Builds aerobic fitness.
- Zone 3, Tempo Moderate effort, improves endurance.
- Zone 4, Threshold, Hard but sustainable, increases FTP.
- Zone 5, VO2 Max, Very hard, boosts max aerobic power.
- Zone 6, Anaerobic Capacity, Short, high-intensity bursts.
- Zone 7, Neuromuscular Power, Explosive efforts , sprints.
Training Stress Score or TSS
It is also known as Load in several platforms to respect the copyright of this term.
TSS is a number that estimates how much strain a workout puts on your body. It considers both intensity measured with power and duration.
A short, hard ride can have the same TSS as a long, easy ride.
100 TSS roughly equals one hour at your FTP.
A long endurance ride at low intensity might also add up to 100 TSS, but it won’t be as fatiguing as a high-intensity effort.
TSS helps track training load over time. Too much can lead to overtraining. Too little might not lead to progress. Managing TSS helps balance fitness and recovery.
Average Power
This is the simple average of all power data from a ride. It doesn’t consider variations, so it’s not the best measure of effort.
Normalized Power or NP
Normalized Power gives a better estimate of how hard a ride felt compared to average power. It accounts for changes in effort, like hills, sprints, and coasting.
Average power doesn’t tell the whole story. A ride with constant effort (like on a trainer) and one with surges (like a race) could have the same average power, but the race feels much harder.
NP corrects for these variations by giving more weight to harder efforts.
For example, a ride with an Average Power of 140 Watts may have a Normalized Power of 178 Watts if the ride had lots of bursts or ups and downs.
Intensity Factor
It is also known as Intensity in several platforms to respect the copyright of this term.
Intensity Factor measures how hard a ride was compared to your Functional Threshold Power, FTP.
It’s a simple way to see the effort level of a workout or race.
The intensity factor is calculated by dividing Normalized Power by FTP
Values range from 0.0 to 1.5, but most rides fall between 0.5 and 1.05.
What the Intensity factor Values Mean for your training:
- From 0.50 to 0.75 is an Easy endurance ride.
- From 0.75 to 0.85 is a Moderate training ride.
- From 0.85 to 0.95 is a Hard training session.
- From 0.95 to 1.05 is a Race effort or very intense workout.
- Above 1.05 is All-out efforts, shorter than an hour.
Why is Intensity factor useful?
- Helps gauge effort without relying on distance or speed.
- Useful for planning recovery—higher Intensity factor rides need more rest.
- It is a key part of Training Stress Score calculation.
By tracking Intensity factor, you can balance hard and easy rides for better training progress.
Efficiency Factor or EF
It is also known as Efficiency in several platforms to respect the copyright of this term.
Efficiency Factor is a measure of how efficiently your body converts effort into power. It helps track improvements in aerobic fitness over time.
EF is the ratio of Normalized Power to average heart rate for a given ride or interval:
This means the efficiency factor shows how much power you produce for each heartbeat. A higher EF suggests improved efficiency, your body is generating more power at the same heart rate.
It is useful for:
- Tracking Aerobic Gains: If your EF increases over time, it means you’re becoming more aerobically fit. You can produce more power without your heart working harder.
- Comparing Similar Efforts: EF should be compared under similar conditions. same type of ride, similar fatigue levels, and environmental factors.
- Detecting Fatigue: If EF suddenly drops, it may indicate accumulated fatigue or overtraining.
Variability Index or VI
Variability Index measures how steady or inconsistent your power output is during a ride. It helps determine whether your effort was smooth and controlled or full of surges and fluctuations.
Variability Index is the ratio of Normalized Power to Average Power
Since Normalized Power accounts for power spikes and variability, a higher Variability Index means the ride had more fluctuations in effort.
Low Variability Index values from 1 to 1.05 mean Steady effort, common in long, steady-state rides like time trials and endurance rides.
High Variability Index values above 1.1 mean a Variable effort, Found in races, group rides, or interval sessions with big power swings.
Why is Variability Index Important?
Time Trialists and Endurance Riders: A lower Variability Index means a more controlled and efficient effort. This conserves energy and helps maintain a sustainable pace.
Road Racers and MTB Riders: A higher Variability Index is normal due to frequent surges, climbs, and attacks. However, excessive variability can lead to early fatigue.
Indoor vs. Outdoor Training: Indoor rides usually have a lower Variability Index since terrain and coasting don’t affect power output as much.
Work
Work is the total energy used in a ride, measured in kilojoules. More work means more calories burned.
Power-to-Weight Ratio or PWR
Power-to-weight ratio is a key performance metric in cycling. It measures how much power you produce relative to your body weight and is expressed in watts per kilogram.
PWR is crucial because it determines how efficiently you can move your body weight on the bike, especially when climbing.
A cyclist with a higher PWR can maintain speed with less effort compared to a heavier rider producing the same absolute power.
Climbing: The higher your PWR, the easier it is to climb. Gravity is the main resistance, so lighter riders with high PWR excel in long climbs.
Flat Terrain: Absolute power, raw watts matters more than PWR because aerodynamics, not gravity, is the biggest force to overcome. Heavier, more powerful riders often perform better in flat races.
Sprint Performance: PWR is less important than peak power output. A sprinter relies on explosive power, which isn’t directly dependent on body weight.
Chronic Training Load or CTL
It is also known as Fitness in several platforms to respect the copyright of this term.
CTL represents your long-term training load and is often referred to as your fitness level.
It is calculated based on your daily Training Stress Score, TSS, over the past 42 days, providing a rolling average that helps track trends in your training.
A rising CTL means you are building endurance, strength, and overall cycling fitness.
If CTL drops significantly, you may be losing fitness due to reduced training.
Rapid CTL increases can signal overtraining and potential injury.
Your Available Training Time Sets Your CTL Ceiling
CTL is directly linked to how much time you can train. Since CTL is based on daily TSS, the more hours you ride, the higher your potential CTL. However, everyone has a CTL ceiling based on their available training time.
- If you train 5-7 hours per week, your CTL will likely top out around 50-70.
- With 10-12 hours per week, you may reach 80-100.
- Riding 15 or more hours per week can push CTL to 120 and above, common for elite cyclists.
- If you cannot train more hours, raising CTL further requires smarter intensity management, such as structured interval training to maximize the effectiveness of available time.
CTL Ranges – What’s a Good Number?
CTL values vary based on experience, training time, and goals:
- Beginner Cyclist, riding from 3 to 5 hours per week can get to CTL from 20 to 50
- Intermediate, doing Regular Training, No Racing and from 6 to 10 hours per week can get to CTL from 50 to 80
- Competitive Amateur Racer training 10 to 15 hours per week can get to CTL from 80 to 120
- Elite and Pro Cyclists with 15 or more hours per week can get a CTL above 120.
- Important note: CTL is a fitness indicator, not a performance guarantee. A high CTL without proper recovery can lead to fatigue.
Ramp Rate
Is the speed at which CTL increases.
CTL should gradually increase over weeks and months. A typical ramp rate is 3 to 5 points per week for sustainable progress.
If you increase CTL too quickly, with ramp rate above 6 to 8 points per week, you risk overtraining.
If your ramp rate is below 3 points a week you are not training enough to improve.
Acute Training Load or ATL
Also known as Fatigue in several platforms to respect the copyright of this term.
ATL measures your recent training stress over the last 7 days. It represents how much fatigue you’ve accumulated from your recent rides.
Unlike CTL, which tracks long-term fitness, ATL tells you how tired you are right now.
If your ATL is high, your body is under a lot of stress, and you may need more recovery.
A low ATL means your training load is light, and you may be ready for harder efforts.
Balance is Key. Training is a constant cycle of stress and recovery. If ATL is too high for too long, you risk overtraining. If it’s too low, you may not be pushing hard enough to improve.
For long-term progress, it is important to manage the balance between ATL and CTL through TSB.
Training Stress Balance or TSB
Also known as Form in several platforms to respect the copyright of this term.
Training Stress Balance, TSB, is a measure of how fresh or fatigued you are based on your recent training load. It helps you decide if you should push harder, maintain, or back off in your training.
TSB is the difference between your Chronic Training Load, CTL and your Acute Training Load ATL.
Since ATL reacts more quickly to changes in training than CTL, the difference between them, TSB tells you whether your training has been ramping up, steady, or decreasing.
How to Use TSB for Training and Racing
- Building Fitness: During a training phase, TSB will usually be negative because you are stressing your body. Values in the -10 to -30 are normal.
- Values from -10 to 5 is a grey zone that should be avoided and used only as a transition to tapering.
- Tapering for a Race: Before an important event, you want a positive TSB from 5 to 25 to be fresh but not detrained.
- Values lower than -30 put you in the overtraining zone and should be avoided. Consistent negative TSB of -30 or lower means you may need extra recovery days.
- A TSB above 25 means a prolonged rest period such as that between seasons or as recovery between two major events.
Phenotype
Phenotype in cycling refers to your natural strengths as a rider, based on your power profile and physiological characteristics.
It helps you understand what type of rider you are and what kind of efforts suit you best.
Cycling phenotypes are determined by your power duration curve, the maximum power you can sustain over different time periods such as
5 seconds, 1 minute, 5 minutes, 20 minutes. This data helps categorize cyclists into different types.
Common Cycling Phenotypes
Sprinter:
Strong in short, explosive efforts from 5 to15 seconds.
High anaerobic power and fast-twitch muscle dominance.
Ideal for sprint finishes, criteriums, and short climbs.
Time Trialist
Excels in long, sustained power efforts (20-60 minutes).
High FTP (Functional Threshold Power) and strong aerobic endurance.
Ideal for time trials, solo breakaways, and long steady rides.
All Rounder
Well-balanced across short, medium, and long efforts.
Good but not exceptional in any one category.
Ideal for stage races, mixed terrain, and endurance events.
Pursuiter
Best at 1 to 5 minute efforts like breakaways and short climbs.
Strong anaerobic capacity and good endurance.
Ideal for criteriums, punchy climbs, and attacks.
To support your self coaching journey get our free guides that you can download right now, including:
The Self-Coached Cyclist Training with Power: Concepts
Advanced Cycling Planned Workouts in Intervals.icu Video Tutorial
Cycling Fitness CTL Planning Worksheet
The 2025 Cycling Fitness TSS & CTL Planning Worksheet
As well as our full featured eBook The Self Coached Cyclist Training with Power, covering everything from training concepts to performance tracking.
and check out our Power Based Training Plans.