This document provides an overview of key power meter terminology used in cycling training. It defines important terms like watts, functional threshold power (FTP), training zones, normalized power, variability index, intensity factor, watts per kilogram, matches, and training stress score. Understanding these terms allows cyclists to precisely measure and analyze their power output, workload, and training progress.

1. The TrainingPeaks Guide to Cycling Power Terminology
An athlete’s guide to understanding the key terms of training with power.

2. “It is the most effective tool you can get
to go faster on a bike.” - Joe Friel

3. Introduction
Training with a power meter is the most precise and detailed way to get results.
But the power meter is only part of the equation, you need to know what the
numbers mean and how to interpret them. There are a few key terms you need
to understand to take full advantage of this amazing tool. The following slides
will explain what these terms mean and how they apply to your training.

4. Watts
Simply put, a watt is a measure of
power per unit time. To be more
precise, it is 1 joule per second.
Unlike heart rate, watts do not fluctuate
due to outside factors. 300 watts is 300
watts no matter what speed you are
going.
Watts are the most precise way to truly
measure your effort.

5. Functional Threshold Power (FTP)
Popularized by Hunter Allen and Dr.
Andrew Coggan in their book, Training
and Racing with a Power Meter,
the term Functional Threshold Power,
or FTP, refers to the maximum power
you can sustain evenly for one hour.
Your FTP can be determined during a
lab test, by performing a field test, or
estimated from a race or hard workout
in training.

6. Determining FTP
This test was created by Hunter Allen and is a simple way athletes can test
their FTP. Perform this field test on a flat course relatively free of stop signs or
traffic, and if possible one that has a steady, uphill grade of less than 5%. The
uphill grade helps you to maintain a constant output, as opposed to rolling
terrain where it’s difficult to keep your power up on the downhills.
Test
• 15-minute endurance paced warm-up.
• 3 x 1 minute fast pedaling drills of at least 100 rpm with 1-minute recoveries in
between each.
• 20-minute time trial all by yourself—no training partners, and not in a race.
Your effort should be done as if it was a race for the entire 20 minutes—all out,
but sustainable for the 20 minutes.

7. Determining FTP
Your average power for that 20 minutes, less 5%, is an approximation of your
FTP. For example, if your average power for the 20-minute test was 250 watts,
then your FTP is 250 watts x .95 = 238 watts.

8. Zones
Once you know your FTP you
should set up your power
training zones. Each zone
works a different physiological
system. Using your power
meter allows for greater
precision and targeting of
specific zones.
This is where the detailed data
from a power meter is much
more beneficial than data from
a heart rate monitor.
This table created by Dr.
Andrew Coggan shows the
performance benefits from
training in zones 1-7.

10. What Do the Numbers Mean?
Along with your power meter, you’ll need a device to display and record the
data. There are many terms and acronyms that you need to know to
understand what you see on the screen and to analyze your file post-ride. The
following terms are the most important metrics you need to understand in order
to use your power meter to it’s fullest.

11. Average Power
Average power is simply the numerical average power you put out for a given
time. Many devices come with non-zero averaging or smart recording turned
on. This means the device won’t record zeros when you are not pedaling. While
this will make your numbers look better it is not a true accounting of your effort
and we recommend you turn that function off.

12. Normalized Power® (NP®)
No ride is perfectly steady. Your power output varies due to factors like wind,
terrain and other riders. Here’s where Normalized Power (NP) comes in. This
algorithm is somewhat complicated, but it incorporates two key pieces of
information:
• The physiological responses to rapid changes in exercise intensity are not
instantaneous, but follow a predictable time course.
• Many critical physiological responses (e.g. glycogen utilization, lactate
production, stress hormone levels) are curvilinearly, rather than linearly, related
to exercise intensity.

13. Normalized Power® (NP®)
Your NP is an estimate of the power you could have maintained for the same
physiological “cost” (in terms of glycogen utilization, lactate production, stress
hormone levels, and neuromuscular fatigue) for a given effort or ride if your
power output had been perfectly constant (e.g., as on a trainer) rather than
variable. As such, NP is always higher than average power.
NP is a better indicator than average power of how metabolically challenging
your workout was. It emphasizes power surges which require a lot of glycogen
(carbs) and therefore contribute to an increase in fatigue.

14. Normalized Power® (NP®)
An example is if you pedal at 200 watts for 1 hour, you will have an AP and NP
of 200. If you pedal at 100 watts for 20’, 200 watts for 20’ and 300 watts for 20’
you will still have an AP of 200 watts but your NP will be 239 watts.

15. Variability Index (VI)
Variability Index is a way to measure
how smooth or “variable” your power
output was during the ride.
It is calculated by dividing your
Normalized Power by your Average
Power. A steady and even output, like
during a triathlon, should have a VI of
1.05 or less. During a criterium race,
where there would be more coasting
and surging, the VI may be as high as
1.2 or more.

16. Intensity Factor® (IF®)
Intensity Factor provides a valid and convenient way of comparing the relative
intensity of a training session or race either within or between riders, taking into
account changes or differences in threshold power.
The IF of a ride is the ratio of your Normalized Power to your FTP. For
example, if your Normalized Power for a long training ride done early in the
year is 210 W and your FTP at the time was 280 W, then the IF for that workout
would be 0.75. However, if you did that same exact ride later in the year after
your FTP had risen to 300 W, then the IF would be only 0.70.

17. Watts Per Kilogram (w/kg)
Using Watts per Kilogram is the best way to compare two different riders.
Usually expressed as watts per kilogram of body weight (w/kg), the higher the
watts, or lower the weight, the faster the rider will go.
A power to weight ratio of 4 to 4.5 w/kg is equivalent to a competitive Category
2 racer. A power to weight ratio of 5 to 6 w/kg would put you in the range of a
Category 1 elite professional according to Dr. Andrew Coggan’s Power Profile
Chart.

18. Matches
This term seeks to show those points in a race or ride where you exceeded
your abilities and burned energy at a high rate.
A match can loosely be defined as an effort in which you go over your threshold
power by a certain percentage and hold it there for a period of time. The table
below is a guide for what may constitute burning a match. Every rider has a
certain number of matches they can burn. If your burn too many matches it will
be a long ride home.

19. Training Stress Score® (TSS®)
Based off of the duration and intensity of your session, Training Stress Score is
a single, numerical value for the effective load of your training session. You
earn 100 TSS for an all out, 100%, 60-minute workout. Since your FTP value is
the wattage you can hold for 1 hour, holding that value for 1 hour equates to
100 TSS points. Of course most workouts are not completed at 100%, so most
workouts will accumulate less than 100 TSS per hour.
For example, if your FTP is 250 and you hold 200 watts for 1 hour you would
have a TSS score of 80. You can earn more than 100 TSS within a single
workout (as long as it is longer than an hour), but never more than 100 TSS per
hour. If you find that you are accumulating more than 100 TSS points per hour
you have either bad data readings or your FTP needs to be raised. TSS values
are critical to using the Performance Management Chart to track long term data
trends.

20. Putting it All Together
Combining detailed data with an understanding of a few key terms allows you
to analyze each ride and prescribe more exact workouts in the future. You’ll be
able to quantify the true load of your training- for each ride and over time.
Don’t just look at your numbers and wonder, use them to become a faster rider.