All About Power-Based Training - Coach Tip Tuesday

A couple of weeks ago I talked about how fitness devices are not as smart as one might hope.  While this is certainly true, it’s also true that technology can be thoughtfully incorporated into endurance sports training with the right mindset and approach.  This week continues a mini series of Coach Tip Tuesdays where we will discuss certain technologies and how athletes can best implement them.  Last week we covered Heart Rate-Based Training and this week we’re going to dive into Power-Based Training.

What is Power-Based Training?

Power, as it pertains to endurance sports training, is a measure of how much work the body’s muscles are actually doing in a workout or race.  Power-Based Training is training that is set around an athlete’s individual power zones.

In cycling, power is the only objective way to measure an athlete’s performance.  While heart rate is a measure of the body’s response to training and the effort they are putting forth and speedometers quantify an athlete’s results, power measures the actual amount of work an athlete puts out in training or racing.  In cycling, power is measured using a device called a power meter.  Relative to other equipment and gear in endurance sports, a power meter is very expensive.  Therefore, athletes should have a thorough understanding of what this device is and how it is used before they make a decision to purchase one.

Most cycling power meters use tiny devices called “strain gauges” which measure the microscopic flexing of a given drivetrain component (such as a pedal or crank arm) to determine torque, or the amount of force being applied to that drivetrain component.  Power = Force x Velocity  Thus, when torque and cadence (aka leg speed) are measured, the power you are outputting can be calculated.  Power is generated from muscular force (the actual use of one’s body to apply force via the bicycle), cadence, or via a combination of the two.  Athletes can learn how to manipulate these variables to control their power output.  As a result, much like Heart Rate-Based Training, Power-Based Training is a very individualized way to approach training and racing.

Running Power Meters also exist, but as of the time of this writing, they are much more algorithmically-based than cycling power meters.  (And if you recall from my discussion about fitness devices, the more algorithms are involved, the more the data can be inaccurate.)  While cycling power meters do use equations and algorithms to generate power data, they are ultimately measuring the actual torque being applied by the athlete and are not relying as heavily on algorithms to determine what this number is.

Because Running Power Meters are rooted in algorithms, I don’t currently trust their data or encourage athletes to use them in training.  My opinion on Running Power Meters may change as the technology evolves, but this is my current viewpoint on them.  Thus, for the purposes of this article, I will only be discussing Power-Based Training as it pertains to cycling.

How to Implement Power-Based Training

The process of successfully implementing Power-Based Training is very similar to successfully implementing Heart Rate-Based Training:

1. Ensure that you are accurately able to measure your power during exercise.  Use this same measuring device throughout the entire process of Power-Based Training.
2. Determine your Functional Threshold Power (FTP) via testing.
3. Design training around those power zones.
4. Stick to a training plan designed around power zones consistently for at least three months.

Accurately Measuring Power

In order to train by power, an athlete does need to have a properly functioning power meter.  As I’ve discussed in the past, it’s important to ensure that the data being collected is accurate because bad data is worse than no data.  When it comes to power data collection, there are a few important things to keep in mind:

• The two most common types of power meters are pedal-based and crank-based.  Both types of power meters are currently 99% accurate, so one is not inherently superior to the other when it comes to accuracy.
• Smart trainers can be used as effective power meters (especially if they are direct drive smart trainers (where you take the rear wheel off of your bike to use the trainer)).
• Athletes training with power should always record heart rate data along with their power data.  The relationship between these two data points is important and gives greater context to the overall picture of what happened in a given training workout or race.
• Power meters should be calibrated independently with each recording device being used by the athlete before each and every ride.
• For instance, this means if you are using a cycling computer and a watch and recording workout files on both, you need to calibrate your power meter independently to each of those devices.
• The same measuring device (aka power meter) must be used throughout all of your Power-Based Training.
• If you have a smart trainer and a power meter, you should use your power meter as your power source when riding the smart trainer.  You should not switch back and forth between the two measuring devices.
• Virtual Power (calculated using a speed sensor combined with a cadence sensor) is possible in the absence of a power meter or smart trainer when using indoor training platforms such as Zwift or TrainerRoad, but this is a completely algorithmically-generated method of training with power, and thus cannot (and should not) be treated the same as using a power meter or smart trainer.

Determine Your Power Zones

In order to successfully implement Power-Based Training, you must determine your own personal power training zones via threshold testing.  This test is commonly called a “Functional Threshold Power Test” or FTP Test.  An FTP Test determines an athlete’s Functional Threshold Power (FTP) and this number is used to generate one’s personal power zones (which are all a certain percentage of one’s FTP).

It’s extremely important to understand that the “default” training zones established by algorithms (read: by Garmin Connect or any other training software or device) are not accurate.  Ever.  As a general rule, I don’t deal in absolutes, but this is one instance where I will.  No algorithm can ever accurately determine what your personal power zones are.  You must do a threshold test to accurately determine them.

It’s also important to note that power zones are very individualized.  One person’s maximum power output can and will vary greatly from another athlete’s.  Thus, it’s unwise to compare one’s FTP to someone else’s.  If seeking a comparison point, Power-to-Weight Ratios are a more accurate measure.  Power-to-Weight Ratio is a measurement of your power on the bike in comparison to your body weight.  It is expressed as watts of cycling power produced per kilogram of body weight, abbreviated as W/kg.

There are several different types of FTP Tests that can be utilized to determine power zones.  Which one is best depends on a lot of factors; I’ll overview the most common one I use here: Conduct an easy warm-up for 15 minutes, and then go as hard as you can sustain without stopping or resting at all for 20 minutes.  The data gleaned from that sustained harder effort can then be used to calculate your personal training zones.  As an added bonus, this test can be used to determine both power training zones and heart rate training zones.  (For more details on how you can determine your own training zones, please connect with me.)

Threshold testing like this is one of the only times in training where the workout must be completed exactly as it is planned.  If any mistakes or modifications are made, the data is useless and must be discarded.  Remember: The only way this type of training works is if the baseline data is accurate.  So, if they cannot complete the test exactly as planned, the athlete needs to redo the test, but there’s a waiting period involved.  Since these tests do ask athletes to go their hardest, there needs to be a period of recovery before the athlete will be truly ready to go their hardest again.

Design Training Around Power Zones

The next step is to design training that is based off of your own personalized power zones.  This means that you will complete workouts while monitoring your power and staying within the prescribed zone as planned.

Because power is an instantaneous measure of the work being done by the body, I have found that monitoring rolling averages is the most useful thing in training, especially when completing specific workouts that contain intervals.  Many devices (such as Garmin) have an option to display the 3-second, 5-second, 10-second, or 30-second power average. 

Normalized Power (NP) is also a very useful power metric to implement and monitor in training.  Normalized Power is a formula that weights hard efforts and deemphasizes easy spinning in a given ride.  Simply put, Normalized Power approximates what you could have done in a ride with the same level of effort if you rode at a perfectly steady pace for the entire ride.  

Average Power differs from Normalized Power in that it is a number that represents what the rider actually did during a ride (including coasting).  This number can be misleading; the Average Power of an interval workout will actually often be low because the time between hard efforts is spent soft pedaling or coasting.  Most athletes understand that an interval workout like this is more fatiguing than if they ride at a steady endurance effort for the same overall duration of time.  Normalized Power is designed to account for this.

Stick to it for at Least Three Months

As you’ve heard me say so many times over the years, consistency is extremely important in all endurance sports training, but it’s especially important in Power-Based Training.  This is true both in one’s use of the measuring device (meaning that the same power measuring device must be used for all training/racing for accurate data) and in the athlete’s actual training.

In order for athletes to derive the benefits of Power-Based Training, an athlete must stick to a training plan designed around power consistently for at least three months.  When I say “a training plan designed around power,” I mean that at least 95% of the workouts in those three months must be designed around power and completed by sticking to the prescribed power targets in that workout.  Doing this type of training in one workout once a week will not yield the intended results; it must be done consistently in almost all workouts.

In my experience, this is definitely the biggest challenge for athletes, and it’s where most athletes “fail” at Power-Based Training.  It’s not uncommon to hear “Power-Based Training didn't work for me” and the root cause of that statement is that the athlete wasn’t willing to stick with the plan day-in-and-day-out for at least three months.

During this time, athletes will have to get used to continuously monitoring their power, whether they are riding indoors or outdoors and regardless of the terrain they are riding.  This can be quite the challenge for some athletes, as it may require going much slower than they have in the past or than they want to.  They may also find it challenging to hit higher power targets on their own using muscular force. 

The Benefits of Power-Based Training

Power-Based Training is extremely useful for helping athletes develop self-awareness.  Over the course of my coaching career, the most valuable use of Power-Based Training is to help athletes learn what “easy” really feels like and what “slow” really is.  By teaching athletes this, Power-Based Training can reduce the risk of fatigue and overtraining.  

On the other side of the coin, this type of training can be really useful to help push athletes who are naturally conservative into the training efforts and zones that are necessary in order to elicit adaptations in the body and therefore make gains in endurance sports.  For athletes who are afraid to push themselves, Power-Based Training can provide an effective and safe framework for them to do so.

Power-Based Training can enable athletes to more effectively track their effort in interval workouts (workouts where there are intervals completed at a higher intensity).  In my experience, this is especially valuable for tempo workouts, where dialing in on the proper exertion level is really important to benefit from the workout.

Simply put, Power-Based Training can help athletes calibrate their own Rating of Perceived Exertion (RPE), which is one of the most important and useful things any athlete can ever learn.

The Limitations of Power-Based Training

Like all things, Power-Based Training does have its limitations.  One of the biggest ones is paradoxical, because it’s the same reason why Power-Based Training is valuable as a training tool in the first place: Power is a measure of the actual work being done by the athlete, regardless of ambient conditions or other factors.

Though it is a wonderful tool, power is always relative to what is happening in the body.  Other metrics such as heart rate, Rating of Perceived Exertion (RPE), motivation, and fitness round out the picture to provide a clear view of how a given day is going for you.  Relying on power exclusively can be a really big limiter.  It can hold an athlete back if all things are “in sync” on a given day, and it can push an athlete too far if they are having an off day and are still trying to hit a certain power number they feel they “should” be able to hit.

Because of this, it’s important to continually hone self-awareness so you can accurately determine when other stressors or conditions are in play that are impacting your effort levels on a given day.  When this is the case, it’s important to modify your strategy and use a combination of RPE along with power to guide your training for the day (or your race plan if there are additional stressors in play on race day).

The Bottom Line

Once an expensive tool accessible only to the best cyclists in the world, power meters have become incredibly accessible in the last decade, especially with the rise in popularity of smart trainers and indoor training platforms such as Zwift and TrainerRoad.  75% of the athletes I currently coach train using Power-Based Training (up from 10% a mere six years ago).  I’ve seen how it can be a really effective and useful way for athletes to train and develop racing plans.  Athletes who are willing to invest in this technology and to apply themselves to learn how it works have the ability to unlock a wonderful tool in their Athlete's Toolbelt.