A question that often arises for runners is how intense each of their runs should be. We often believe that doing MORE will get us better results, but research shows that we would be better off steering away from this mindset.

This blog post on the 80/20 rule aims to clarify the intensity at which we should train as runners to get the most benefits and minimize stress on our bodies. Let’s dive in!

What is intensity when it comes to running?

When we train, many variables can be modified to give our training a different outcome. Mainly, there is the frequency (how often), duration (how long), and intensity (how hard).

In this blog post, we will be focusing on intensity which is often the variable that is the most difficult to manipulate.

Intensity can be measured in many different ways, some are objective (based on data) and some are subjective (based on feeling). Examples of objective data to measure intensity are the percentage of maximum heart rate (% HRmax) or blood lactate levels. A subjective way to measure intensity would be using the rate of perceived exertion (RPE) rating effort from 0-10 (Borg Scale) (Kenneally et al., 2018).

The 3-Zone Model

A model based on lactate threshold intensity has been studied by Dr. Stephen Seiler and described in the International Journal of Sports Physiology and Performance. This model describes 3 zones with different blood lactate concentrations. See figure 1 below to get better visuals of this concept (Seiler, 2010).

Simply put, lactic acid or lactate is a substance that is usually present at low levels in our blood. When we exercise at a lower intensity, our energy is produced with the help of oxygen and the lactate levels remain relatively low and stable (aerobic activity). When we exercise at a more intense level, we start producing energy without oxygen (anaerobic activity) and muscle tissue, as well as red blood cells, produce lactate which increases its concentration in our blood.

To come back to these 3 zones, Seiler divided them into low-intensity training (LIT), threshold training (ThT), and high-intensity training (HIT). These 3 intensities of training respectively have increasing levels of blood lactate. The goal of Seiler’s research was to determine where endurance athletes should situate themselves to get optimal results for training intensity and duration.

In other words, this is described as the training intensity distribution (TID). How much time should we be spending in each zone?

Interestingly, it was highlighted in Seiler’s research that an 80 to 20 ratio of low-intensity training to threshold/high-intensity training gave the best results in the long run, pun intended.

The same paper emphasizes that high-intensity training is still an important component of training programs, but that 2 sessions per week are enough to induce performance gains without causing excessive stress to the body (Seiler, 2010).

So what does this mean when it comes to running?

These findings are a game-changer for runners. This means that we don’t have to go all out on each run and feel completely burnt out, which unfortunately happens to so many runners.

In other words, 80% of our running training should feel easy and be at low intensity (zone 1). The other 20% should feel difficult to hard at a mix of threshold and high-intensity training (mix of zones 2 and 3). This is the basis of the 80/20 running rule.

To better visualize this, I have prepared two different charts below. The first one (Figure 2) illustrates the different zones and how to assess this with your percentage of maximum heart rate and/or rate of perceived exertion (RPE). The second chart is the RPE scale and I have color-coded it to represent the different intensity zones.

You can see in the above chart that a runner doing low-intensity training (zone 1) should be able to talk during their run and be anywhere from 0-4 on 10 for perceived effort. An easy way to determine your maximum heart rate is to use the formula (220-age). If you are 40, your maximum heart rate would be 180 bpm. If you are doing a low-intensity run you would want to be at 144 bpm or under (80% of 180 bpm). The same principle applies to threshold and high-intensity runs.

Concrete examples of the 80/20 rule in a training plan

To use the 80/20 rule, you need to know what your weekly volume is. For that, you can either use your total distance or minutes of training for a given week. Keep in mind that when designing running plans, a general guideline is that we don’t want to increase the volume by more than 5-10% per week. This will be another post entirely.

Example #1: Lucy will be running 30 km in the next week. She runs 5 times per week.

80% of her distance ran should be low-intensity and 20% threshold to high-intensity.

80% of 30 km is 24 km. 20% of 30 km is 6 km. Lucy could technically run three 8 km easy runs and two 3 km harder runs. However, running intensely for 3 km might not be the best option. Let’s have a look at what her week might look like.

Example # 2: Nick will be running 100 minutes this week. He also runs 5 times per week.

80% of 100 minutes is 80 minutes. 20% of 100 minutes is 20 minutes. Let’s see what we can come up with for a 1-week plan.

These are just examples to illustrate what the 80/20 rule for running could look like weekly. However, this will look different for each runner depending on their goals, strength training plan, and cross-training.

If we want to expand on different ways to structure training, three main styles of training intensity distribution (TID) have been described and studied: pyramidal, threshold, and polarised. These types of training also base themselves on the different intensities (zones 1 to 3) and how much time should be spent in each zone (Kenneally et al., 2018).

Here is an illustration of each type of training and approximately how much percentage of the training is spent in each zone.

Figure 4 —3 Styles of Training Intensity Distribution (TID)

In a 2018 systematic review, Kenneally et al. (2018) concluded that polarised and pyramidal were more effective than threshold training in endurance runners. If you look at the chart, polarised and pyramidal training each spends about 80% of training at a low intensity. The other 20% is distrusted (although differently) in zone 2 and 3. This matches the 80/20 principle described earlier. It just shows that there are different ways to distribute the 80/20 ratio within a training plan. There is no one size fits all, yet again!

Here are a few tips to summarize and include the 80/20 rule in your running:

• Be clear on your weekly volume (distance or time) and establish your 80/20 ratio from there

• Slow down your easy runs, you should be able to talk

• 2 times per week of higher-intensity running is enough

• The 80/20 ratio can be within the same workout

• And most importantly, it doesn’t matter if it’s not exacted to the minute or km, have fun with it and test out different things

Now get out there and start applying that 80/20 rule, you got this!

Happy running,

April

References:

1.       Kenneally, M., Casado, A., & Santos-Concejero, J. (2018). The Effect of Periodization and Training Intensity Distribution on Middle- and Long-Distance Running Performance: A Systematic Review. International journal of sports physiology and performance, 13(9), 1114–1121. https://doi.org/10.1123/ijspp.2017-0327

2.       Manzi, V., Iellamo, F., Impellizzeri, F., D'Ottavio, S., & Castagna, C. (2009). Relation between individualized training impulses and performance in distance runners. Medicine and science in sports and exercise, 41(11), 2090–2096. https://doi.org/10.1249/MSS.0b013e3181a6a959

3.       Micah Zuhl, Ph.D (2020). Tips for Monitoring Aerobic Exercise Intensity. ACSM, https://www.acsm.org/docs/default-source/files-for-resource-library/exercise-intensity-infographic.pdf?sfvrsn=f467c793_2

4.       Seiler S. (2010). What is best practice for training intensity and duration distribution in endurance athletes?. International journal of sports physiology and performance, 5(3), 276–291. https://doi.org/10.1123/ijspp.5.3.276