Over-under training is a type of interval training that alternates between intensities above the anaerobic threshold or FTP and those below it. The primary objective is to accumulate fatigue and lactate during the “over” interval and then efficiently clear it during the “under” interval. But how can coaches ensure they’re getting the intensities just right for their athletes? Let’s dive in.

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Example Over-Under interval workout: 2 sets of 4x2min. at 105% AT, 4x1min. at 95% AT. 5 minutes recovery in between intervals.
Example Over-Under interval workout: 2 sets of 4x2min. at 105% AT, 4x1min. at 95% AT. 5 minutes recovery in between intervals.

There are multiple ways to do over unders. The only thing that is “set in stone” is that you alternate intensities above anaerobic threshold (AT, over) with intensities below threshold (under). Both the over and under typically take about 30 seconds to 5 minutes.

Here’s an example of Over-Under interval workout:


  1. Warm-up
  2. Over: 3 times 2 minutes, at an intensity of 105% AT
  3. Under: 3 times 1 minutes, at an intensity of 95% AT
  4. Sets: 2 sets with 5 minutes active recovery between sets
  5. Cool-down

This workout would take roughly 25 minutes (ex warm-up and cool down), but it’s far from optimal. However, with the insights provided by INSCYD, coaches can optimize such workouts, ensuring that athletes are training at the right intensities for the right durations.

The intensity of the over unders doesn’t leave much room for error. There are 4 ways you can easily mess up your over-unders:


  1. Your “over” is too intense or too long: you accumulate too much fatigue and won’t be able to finish the workout.
  2. Your “under” is too intense or not long enough: you won’t be able to recover from the lactate accumulation.
  3. The recovery between sets is too short, too intense or too slow: you’ll not recover sufficiently for the next set.
  4. Contrary to number 1,2,3 you can also create over-unders that are not challenging enough, which means you don’t get the desired adaptations.

Using existing workouts (e.g. from Zwift) is not going to be the solution, because they are based on FTP, which is not a good metric for creating individual over-unders. 

Fortunately, you can easily create over-unders that are highly tailored to your needs. Here’s how!

The most important step when creating interval training:

Stop using FTP or anaerobic threshold (AT) for creating interval training.

Simply because you can’t compare what happens in my body at 120% FTP to what happens in your body at 120% FTP.

Moreover, there are easier and better ways to describe your interval training. Let’s use the same protocol as in the example workout: 3 times 2 minutes over, 3 times 1 minute under. The idea is to accumulate lactate during the “over” and to recover from the lactate accumulation during the “under”.

Every athlete is unique, by leveraging the lactate recovery and accumulation graph from the INSCYD performance software to create workouts rooted in science and based on the unique metabolic profile of an athlete

Here’s an example graph from a runner, using pace and running power in training.

INSCYD metabolic testing results:Lactate accumulation and recovery in trail running
INSCYD lactate recovery (grey) & accumulation (purple) graph, depending on the exercise intensity (x-axis). Example from a runner who uses pace and power.

The anaerobic threshold of this runner is where the grey and purple lines meet. There’s no lactate accumulation nor recovery at this intensity of 295 watts.

At a running power of 330 watts, this runner accumulates 1.5 mmol/l per minute. If we use this intensity during the two minute “over”, the athlete accumulates 3 mmol/l per “over”.

At a running power of 250 watts, this runner recovers 0.7 mmol/l per minute. If we use this intensity during the “under”, the athlete recovers 0.7 mmol/l per “under”. If we assume a resting lactate value of 1.5 mmol/l, the set looks like this:


  • Pre set lactate value: 1.5 mmol/l
  • Over: +3
  • Under: -0.7
  • Over: +3
  • Under -0.7
  • Over: +3
  • Under: -0.7
  • Post set lactate value: 8.4 mmol/l

Since our example athlete has a maximal lactate concentration of 12.5 mmol/l (given in the INSCYD metabolic profile), this set will be challenging but doable.

If we now want to make sure the athlete is back to pre-set lactate values, we need to make sure 6.9 mmol/l is cleared during recovery (8.4 – 1.5 = 6.9). Notice that this athlete recovers fastest at 210 watts running power. This should make sense: you need to keep moving to recover. If you lay down on the ground, you don’t feel recovered when getting up.

At a running power of 210 watts, this runner recovers 0.8 mmol/l per minute. As a result we need 8:40 min:sec to fully recover between sets (6.9 ÷ 0.8).

You can now play around with these numbers to create several challenging but doable over-unders. Notice that you’re now using the metric that actually matters (lactate recovery and accumulation) instead of a generic FTP.

For those interested in a deeper dive into the science of lactate accumulation and its significance in training, we’ve prepared a comprehensive whitepaper. Enhance your understanding and apply these insights to your training strategies:

Learn more about Lactate accumulation & recovery. Download our whitepaper!

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With this metabolic data, you could for instance decide not to fully recover between sets, or to pre-load your under-over intervals.

For coaches and labs

Understanding the intricacies of over-under interals is just the beginning. With INSCYD, you can delve deeper into the science of training, tailoring intervals and training programs to each athlete’s unique physiology, optimizing every session for maximum results. Want to see INSCYD in action – book your exclusive Free Demo and discover how it can revolutionize your coaching approach

For athletes

Athletes why train with generic plans when you can have a program tailored to your unique physiology? INSCYD is the key to unlocking your full potential. Find your dedicated INSCYD coach or lab here. Already have a coach? Experience INSCYD in action with your coach and redefine your training approach.

So after diving into the concept of over-under and the importance of tailoring workouts to an athlete’s unique physiology, you might be wondering about the broader science of training intensities. Why do many training programs rely on the anaerobic threshold or FTP? What are the potential pitfalls and how can they be avoided?

To answer these questions and more, we invite you to watch our in-depth webinar presented by Sebastian Weber, a renowned expert in the field. In this session, Sebastian delves into the physiological definition of the anaerobic threshold, its relevance in competition, and the impact of an athlete’s metabolic profile on training outcomes.

There are several benefits attributed to over-unders. Over-unders are designed to improve your:

  • Lactate tolerance, by keeping a high lactate concentration for a relatively long time.

If you can tolerate higher lactate concentrations before you stop exercising, you have an advantage over your competitors. This lactate tolerance has both a physical and a mental aspect. Over-unders can teach athletes to feel the difference between an intensity above vs below threshold. With INSCYD, coaches can monitor this tolerance and adjust training accordingly.

  • Lactate clearance (recovery), by adding “unders” that are relatively high-intensity but low enough to clear some lactate.

An increase in the ability to clear lactate enables athletes to recover faster from high-intensity events like an attack, an uphill segment or any other kind of acceleration. Those who recover faster are probably also able to accelerate more often, which can be race decisive. INSCYD’s detailed metabolic profiles allow coaches to pinpoint the exact intensities at which their athletes clear lactate most efficiently.

  • Lactate shuttle, by switching between HIIT intervals that accumulate vs clear lactate.

The lactate shuttle is a process of moving lactate from a muscle cell that is producing lactate to a muscle cell that is using lactate as a fuel. As a result, no lactate accumulates.

While over-unders might improve these and other performance aspects, they are not the only HIIT interval workouts that do. However, with INSCYD, coaches have comprehensive analytics that allow them to measure, analyze, and optimize any workout type for their athletes.

The best way to find out whether over-unders are the most effective way to improve your performance is to implement them in your training program and do a simple remote test (power- or GPS based performance test) pre- and post training program.

While the basic principle of over-unders remains consistent—alternating between intensities above and below the anaerobic threshold—the magic lies in tailoring these intervals to the unique physiology of each athlete.

The future of coaching is here, and it’s rooted in data-driven insights. Don’t let your competitors get the upper hand. With INSCYD, you can tailor training programs with unparalleled precision, ensuring your athletes achieve their peak performance faster and more efficiently. Book a free demo now and witness firsthand the transformative power of INSCYD. Don’t miss out on this game-changing opportunity!

Athletes understanding your unique metabolic profile is key to unlocking your full potential. If you’re already working with a coach, let’s show both of you how INSCYD can elevate your training. And if you’re on the lookout for expert guidance, our INSCYD-certified coaches are here to help.

If you’re interested in diving deeper into how to create a personalized interval program, watch this webinar. Discover the science and methodology behind creating individualized interval programs rooted in an athlete’s metabolic profile. This video will guide you through the process of setting the right intensities and durations for truly effective training.


Human Movement Scientist | Content Marketing and Education

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