Fresh, Small-Batch Nutrition for Better Health & Performance

Power vs Endurance: How to Measure, Track & Train for Both!

Power Versus Strength

In my previous article (The S:6 Testing Protocol, Part 1) I talked about the importance of testing to track progress at specific interval durations.

I explained how I prefer one longer test (at a specific sub-maximal aerobic heart-rate) to identify aerobic function and three shorter maximal efforts to identify anaerobic power at different levels.

I also introduced the concept of Fatigue Rate. This allows you to track your aerobic fitness (endurance) relative to your top-end strength/power. 

Through training and testing, we attempt to maximize both ends for peak performance. The tricky part, however, is that improvements in one usually result in a decrease to the other. This is why both need to be specifically trained and tracked.

Part 1: Identifying Aerobic Power.

The first part of our testing protocol is our Aerobic Threshold (AeT) Test. This includes a 20:00 sub-maximal interval for best average power at your AeT Heart Rate.

What’s your AeT Heart Rate?

AeT Heart Rate is where you are producing energy from roughly equal balance between fat and carbohydrate. This occurs at approximately 80% of your Maximum Heart Rate

In general, training below this heart rate burns more fat for fuel, and training above it burns more carbohydrate for fuel. We want to train just below AeT HR to maximize our fat-burning, aerobic energy system and build endurance.

The faster we can go while maximizing fat for fuel extends how far and how hard we can go in a race. Improved aerobic fitness preserves precious glycogen stores and allows for more power over greater durations. Maximizing aerobic power should be the goal for every endurance athlete.

Your Aerobic Energy System is trained by your longest workouts. These are your 3+ hour rides and runs at a steady but low intensity. These sessions build your heart function, blood vessels, mitochondria  and fat-burning capacity.

Power versus Endurance - Track and Train

Your Aerobic Threshold (AeT) zone is where “next level” fat burning happens, as well as some power output improvement. Your AeT zone power is the max power you can achieve for 2 to 2.5 hours.

Our test interval is only 20 minutes in duration, so the power you achieve is not your true AeT power. Your power would continue to decline if you were to stay at the target heart rate for another 100 minutes. This 20-minute aerobic power number is still a valuable metric to track and improve over time, however.

Using our Training Zone Calculator you will see your 20-minute AeT power from the test, as well as your true AeT Power calculated from both your Fatigue Rate and the rough guideline of 85% Functional Threshold Power. 


Part 2: Identifying Anaerobic Power and rate of fatigue at longer output durations.

Power versus Endurance - Track and Train

Find your Fatigue Rate, here’s how …

After a solid warm-up from the AeT Test, do a 1-minute, 2-minute, and 4-minute test for max power, each with 4-8 minutes recovery between efforts. With the doubling durations, we can calculate the percentage that power drops off between the 1-minute and 2-minute intervals, and the 2-minute and 4-minute intervals.

This percentage of decline is referred to as your Fatigue Rate. For the moderate to well-trained athlete this Fatigue Rate remains pretty constant as you extend outwards in doubling durations. Example: 4 minutes to 8 minutes, 8 minutes to 16 minutes, 16 minutes to 32 minutes, and so on.

Using our Training Zone Calculator athletes can enter their test results and the spreadsheet gives the  Fatigue Rate percentage and the resulting training zones. 

Not only does the Fatigue Rate help to calculate the training zones, but it sheds light on the “Power vs. Endurance” scale that an athlete is currently experiencing.

A high Fatigue Rate indicates that an athlete slows down at a high rate and could benefit from more endurance training (i.e. more “low-end” aerobic training).

Conversely, a low Fatigue Rate means the athlete's endurance is solid but could use more strength and/or power training.

Over the years I have found that a Fatigue Rate of 8-9% is a good balance point between power and endurance. Thus the goal of training is to not simply achieve this balance point but to continue to increase your “top-end” 1, 2, and 4-minute power numbers while maintaining a Fatigue Rate around 8%. This achieves more power across all durations for superior performance! 

Power versus Endurance - Track and Train

I was first introduced to this concept of declining output percentages and rates of fatigue as a means to measure fitness many years ago at a coaching conference from a running coach, as well as soon afterward from a cycling coach experimenting with power numbers. Since then I have found it to be very insightful with the athletes I have trained over the years.

Our Power Testing protocol does a great job identifying an athlete’s top-end and aerobic power through their Fatigue Rate and AeT Testing numbers. 

The goal is to continually increase short-power numbers through strength and plyometric training in the gym along with careful doses of high-intensity training on the bike. As short duration power numbers rise we also address aerobic fitness on the other end to prevent the Fatigue Rate from getting too high. We do this by incorporating longer endurance rides and/or AeT intervals into an athlete’s program.

This continually sliding scale of power vs. endurance must be constantly addressed to maximize performance.

Want help giving our Aerobic and Anaerobic Power Test at try? Schedule your testing at Sessions:6 HERE.

Part 3 of our Testing Protocol Series will teach you what to do with your results and provide real-world examples from some of our athletes.

You can also purchase our 24-Week Off-Season Trainer Series from Training Peaks that includes our testing protocol as well as a complete build through each energy system to improve your top-end power and fatigue resistant endurance. Check it out HERE.


This article was written by Cody Waite, professional endurance athlete, endurance sport coach and founder of Sessions:6 Sport Performance. Looking for help with your endurance sport training? Check out S:6’s Training PlansTeam Programs, and  Personal Coaching options created to fit your needs and budget.

Leave a comment

Please note, comments must be approved before they are published