To understand power-endurance, we need to look at the legendary Usain Bolt.

Most people think of him as the fastest human of all time, which he undoubtedly is.

But what people don’t realize is that it’s not just his top speed that makes him so incredibly unique. Instead, it’s his ability to slow down just slightly less than everyone else.

In the 100m race, athletes hit their top speed well before the finish line. Usually around 7 seconds in or so. After that, it’s a matter of who can slow down the least.

He wasn’t just incredibly fast. He was also incredibly good at slowing down slower than everyone else. This is what truly set Usain Bolt apart and it’s what defines power-endurance.

It’s not just in sprinting that the difference between winning and losing can come down to the thinnest of margins. The ability to generate that last bit of extra performance when you need it most is what often separates the very best from all the rest.

From a fitness standpoint, the quality that’s often the most important to be able to do this is power-endurance.

This is the ability to maintain your explosive power as long as possible before fatigue sets in and you slow down.

Although there are limits to how much power you can sustain over time due to the nature of producing energy anaerobically (without oxygen), it can still be noticeably improved through training.

One of the best ways to do this is through power-endurance intervals.

Why we can’t be like Superman

Being able to stay in your high gear just a few seconds longer primarily comes down to how well your body can handle the stress that comes with producing a lot of energy anaerobically.

As we talked about in yesterday’s lesson, the body can produce energy aerobically, with oxygen, or anaerobically, without oxygen.

The aerobic system is always producing energy 24/7, from the moment you’re born throughout your entire life. It is incredibly efficient and it can turn proteins, carbs, and fat all into energy.

When it needs to generate more power than the aerobic system is capable of, that’s when it turns to the anaerobic side of things.

This is what makes the body capable of lifting hundreds of pounds of weight and sprinting at 20 miles an hour or more.

The cost of this, however, is fatigue.

If you think about it, there’s a good reason our bodies work like this.

Imagine if you could run an entire mile at the same speed you can hit in a 10 second sprint. Or if you could squat 100 reps with your 1 rep squat max.

Even if this were possible, the amount of stress you’d put on all your tissues and joints would be immense. The real world isn’t a superhero movie and ultimately, it wouldn’t take long before things would break.

Fortunately, we have a built in safety mechanism that prevents this from happening.

The more we use the anaerobic energy systems and the faster we generate energy, the more rapidly we fatigue and become forced to slow down.

The way power-intervals work is to train the body to slow down that fatigue just enough for us to squeeze out a few extra seconds of performance.

They can’t override how our body fundamentally works, but they can help us generate as much power as possible before we slow down.

How to do red and green power-endurance intervals

Both types of power-endurance intervals are extremely similar to the power intervals we covered in the previous lesson. The only real difference is in the times that are used for both the work and the rest periods:

  • Green power-endurance intervals: 10-15s work @100% : 60-90s rest at the top of the blue zone.
  • Red power-endurance intervals: 30-45s work @100% : 90-180s rest at the top of the blue zone.

The overall work to active rest ratio is shifted towards relatively longer work and shorter rest periods. You’ll also notice that the active recovery is at the top of the blue instead of the middle.
This is to focus on training those extra few seconds of power and help the body get used to handling the stress of relying more on the anaerobic energy systems.

Unlike with the power intervals covered in the previous lesson, you should start to feel more and more fatigued with each rep. Pushing yourself towards the edge of your endurance is the most effective way to improve it.

When it comes to choosing exercises, the same guidelines covered in the green and red power intervals apply. You want total body exercises that are capable of driving your heart rate up.

It’s also best to try to avoid exercises that put too much stress on your joints or that are highly technical in nature. Choosing the right exercises will help you avoid developing bad habits as you fatigue and reduce your risk of injury.

How often should you do them?

An important thing to note is that this type of interval is high intensity, very demanding, and best suited for someone that already has a good base of fitness and movement capacity.

If you’re just starting out or you haven’t done any conditioning for some length of time, power-endurance intervals are not the place to start.

WIth that in mind, you can start off incorporating power-endurance intervals into your workout as little as one day a week, but generally two, spread a few days apart, will be the most effective.

They should only be done as part of your green or red workouts.

They can be done with weights in the same workout, but in that case, it’s best to do the intervals first if your goal is to improve your conditioning.

Doing them after you’re already fatigued from lifting will potentially make them less effective and likely slow down your recovery.

A good number of sets is anywhere from as little as 2 and as many as 5-6 depending on your fitness level.

When you’re first getting started, stick with the lower end of the work times and the higher end of the rest guidelines. Each week, add a few more seconds of work in each rep until you get to the higher end.

From there, start to reduce the rest intervals by a few seconds at a time until you’re on the lower end.

A good amount of time to include power-endurance intervals in your program is typically between 4-6 weeks. Just as with the power intervals, it’s normal to see your HRV decrease a bit when you first start incorporating them.

Look for your HRV rebound back up in the following weeks as your power-endurance improves.