Dozens of factors go into designing a training plan for a race. You need to determine how many miles per week, the length of the longest long run, and what types of workouts. Another important factor to consider is how many runs are easy, how many hard, and how many moderate – training intensity distribution. One of the most popular forms of training intensity distribution in the last several years is 80/20 running. However, that is not the only way to distribute training intensity – nor is it always the most effective way. There are several different approaches to training intensity distribution.
To quote exercise scientist Billy Sperlich in a recent Twitter thread: “Seeking a best practice universal TID most likely will not assist personalized training prescriptions…and probably does not exist.”
Training Intensity Distribution for Running
Depending on the season, their goals, and their training background, athletes will use different TID at different times. Recent research begins to point to the idea that you use a training intensity distribution that taxes the physiological systems used in your race during the closest weeks of training. You then use other training intensity distributions when further away from goal races. (This is the approach I take with many of my athletes, particularly when training for the marathon.)
A quick primer on the terminology:
- First ventilatory threshold: Sometimes called aerobic threshold, this is the point where breathing begins to increase. Your body shifts from burning a higher ratio of fatty acids to carbs to a higher ratio of carbs. (Some literature may call this first lactate threshold, but that is different than what runners typically call lactate threshold.)
- Second ventilatory threshold: Also called your anaerobic threshold and lactate threshold. (Some literature may call it “maximum lactate steady state.”) This is the point where lactate begins to accumulate rapidly in the bloodstream. Anaerobic glycolysis (carb oxidation without oxygen) begins to contribute to energy production.
- VO2max: Your maximum oxygen consumption rate – in plainer terms, your maximum aerobic capacity. Lactate accumulates at a very high rate. Anaerobic glycolysis contributes at a more significant percentage (although the energy production is still predominantly aerobic).
In exercise science literature on endurance training, researchers and coaches divide training intensities into three zones. These three zones are easy (Z1), moderate (Z2), and hard (Z3).
- Easy (Zone 1) Below your first ventilatory threshold – easy runs. For most, this is slower than marathon pace.
- Moderate (Zone 2): Between your first ventilatory and second ventilatory threshold. Runs at this intensity include tempo runs, threshold runs, cruise intervals, and marathon pace.
- Hard (Zone 3): Between your lactate threshold and VO2max – hard intervals lasting usually 1-5 minutes. Intensities such as critical speed (harder than threshold, not as hard as VO2max) also fall into this zone.
There are several different types of training intensity distributions for endurance athletes. (Keep in mind: this encompasses cycling, cross-country skiing, rowing, and swimming in addition to running. The lower rates of impact may play a role in why polarized training works so well for XC skiers or cyclists.)
One of the big ongoing investigations in exercise science is which is optimal. Dr. Stephen Seiler pioneered the research on polarized (80/20) training in the 2000s through present. The approach of high-volume, low-intensity training is similar to what you would find in MAF method/low-heart rate training.
Now, more researchers are investigating other forms of training intensity distribution, such as pyramidal and threshold. A highly effective distribution for well-trained endurance athletes is pyramidal training (see: Kenneally et al., 2018 and Stoggl & Sperlich, 2015). Some elite runners employ threshold intensity distribution, with relatively high amounts of time spent at moderate intensities.
Endurance Training Intensity Distributions
As a note, typically training intensity distribution is calculated based on training time in minutes (see here for an example).
POLARIZED: Most runs (~80%) are done in Z1; a significant chunk (~15-20%) are Z3; very little (5% or less) are Z2. You are either running easy or doing hard intervals, without much training at your aerobic or lactate thresholds. Typically, this involves two interval workouts and the remainder of the runs easy.
Note: 80/20 running CAN fall into this distribution. However, some coaches may broaden their definition to include lactate threshold in the 20% hard.
PYRAMIDAL: Most runs are Z1 (80%), followed by a significant portion in Z2 (~15%), with some time but not much spent in Z3 (~5%). You’re doing lots of easy runs and lots of moderate efforts and threshold work, but not many hard intervals. Typically, 1-2 runs are Z2-Z3 workouts, the rest are easy.
Pyramidal can be another variation of 80/20 running, since 80% is easy/20% is quality work (Z2/Z3).
THRESHOLD: A large amount of training (~30%) was done in Z2, with a majority of the other 70% in Z1 and very little in Z3. Many elites do employ it especially if they follow methods such as Canova or the Norwegian models. However, this approach works best in the context of high mileage with runners who tend to be more durable.
HVLIT: High-volume, low-intensity training. This can be a base building phase for many. MAF training also looks like this, with almost all time spent in Z1.
LV-HIT: Low-volume, high-intensity training. Roughly 50% or more of the training is done in Z2 and Z3. If you remember Run Less, Run Faster from the 2010s, that plan followed this methodology. In it, you ran only three times per week, with a large percentage of those miles in Z2 and Z3. This method is more common in endurance sports that have a lower impact than running.
Periodization of Training Intensity Distribution
With some of the most recent research, particularly a 2021 study published in the Scandinavian Journal of Medicine & Science in Sports, we find that periodizing through the different types of training intensity distributions can yield greater improvements in long-term performance. (In this study, athletes who trained with 8 weeks of pyramidal training followed by 8 weeks of polarized training performed best in the 5K. Keep in mind, this is also showing proof for periodization of general to specific.)
Following the idea of intensity being more specific to the demands of the race as you get closer, you can periodize training intensity based on your goal race:
5K/10K: Base phase (HVLIT) -> pyramidal phase -> polarized phase
Half Marathon/Marathon: Base phase (HVLIT) -> polarized phase -> pyramidal phase
Marathon (advanced): Base phase (HVLIT) -> pyramidal phase -> threshold phase
Marathon (Novice): HVLIT
One Final Thought
Individualization does play a role! Some athletes do not respond well to 15-20% of their training at a high intensity. They may easily get injured if they spend too much time in polarized training. Some athletes thrive with lots of moderate intensity (threshold distribution) in marathon training, while some would get injured with this. Novice runners should get comfortable with smaller doses (5-10%) of Z2 and Z3 running before adapting another training intensity distribution.
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Have you ever tried 80/20 running or another approach?
Interesting post, Laura!
I like to follow Garmin’s virtual training plans. They are obviously not personalized but they still seem to work well for me. The one I’m following right now seems to be polarized, many easy runs with two weekly speed work sessions.
I love how you broke this down! I tend to lean towards a pyramidal or polarized approach. I did try Hanson’s a long time ago but ended up modifying it by the end of my training. In general I like to focus on building a strong aerobic base and then gradually add in harder workouts, getting more race specific as it gets closer to the race. It seems like everyone handles those hard workouts differently, and even week by week the intensity may need to be adjusted.
This is so interesting!!! Reflecting on how I train: I tend to run my easy runs too fast and I don’t do enough speed work. I do a lot of cross-training tho and I’m not sure how that all fits into this thinking. Sadly, with the exception of marathon training, I’ve never really taken my training very seriously.
Most of my runs are easy now, with no training, but I do still do some speed work now and again.
Everyone is so different, though, and responds so differently to training loads, so it makes sense to personalize it.
Interesting explanation. It definitely makes sense to personalize your training to fit your current fitness level to avoid injury and work towards goals
I think individualization is key! We all have different mechanics, and strengths (speed vs. endurance)…and we all have different goals.
I don’t really have any running goals right now so most of my runs are at an easy effort. It seems like training can be as simple or complex as you make it.
So interesting! I’ve been in such a weird place with my running (post covid) I think I have close to 100% in Z1.
Oh, that’s very interesting. I had heard about the concept, but never realized it had an actual name. I always learn so much from your posts!
This is so interesting. I learned so much for this and other posts.
It is important as you mention to personalize your training. Runners are different…
Great summary. Is there an error in the Half Marathon/Marathon:
Half Marathon/Marathon: Base phase (HVLIT) -> polarized phase -> pyramidal phase
What it should be (similar to the other paces)
Half Marathon/Marathon: Base phase (HVLIT) -> pyramidal phase -> polarized phase
Thank you for asking! What is written is correct; distances where race intensity is below LT2 are best done with reverse linear periodization and a polarized to pyramidal approach. Zone 2 runs like long tempos are most specific to the demands of a half or marathon. Casado et al. (2022) has a great discussion of pyramidal TID in the practice of elite marathoners. Filipas’ conversation on Koopcast shares his thoughts on pol->pyr for longer distances (his study looked at pyr-> pol as optimal for a 5k).