Which is Better: Block or Mixed-Intensity Periodization for Ultrarunners?

By Jason Koop,
Head Coach of CTS Ultrarunning

Given the same ingredients, trained chefs can create a wide range of dishes. The same is true for trained coaches; we use the same basic training principles and workout ingredients to create training programs for different athletes across a range of sports. Periodization–the ways coaches organize training into weeks, months, and years–can also be designed to address specific demands and time constraints. Two of the main periodization styles we see in endurance and ultraendurance sports are ‘mixed intensity’ and ‘block’. The question is: Which is right for an ultrarunner?

 When I was in college, we had the following weekly routine:

Monday—rest day
Tuesday—5×1000 meter repeats around a grass field (similar to RunningIntervals)
Wednesday—75-minute EnduranceRun
Thursday—6-mile TempoRun
Friday—60-minute RecoveryRun
Saturday—8K cross country race or 5K race on the track
Sunday—90-minute EnduranceRun

Without fail, our entire team had this routine on repeat for nine months during the cross-country, indoor, and outdoor track seasons. Sure, every once in a while we would add some trivial wrinkle, like substituting an eight-mile TempoRun for the six-mile TempoRun, or 400 m repeats instead of 1000s. But the general weekly architecture remained the same, keying in on one RunningInterval workout, one TempoRun, a race (where the intensity would resemble the RunningIntervals), and a long run. This is commonly referred to as a “mixed-intensity micro periodization cycle,” which is an overcomplicated way of saying that your key workouts during the week are at a variety of intensities (RunningIntervals and TempoRun, in this case). Just about every collegiate cross-country program in the United States uses some small variant of this training strategy. It works well for college-aged athletes, partially because they are early in their training arc and partially because their twenty-year-old physiology will adapt to just about anything. That mixed-intensity training structure has been passed down post-collegiately for generations and made its way into the marathon and even ultramarathon realms, albeit with small caveats and nuances that claim to be markedly superior (like substituting 800 m repeats for 1000s or using a progressive TempoRun as opposed to a standard TempoRun).

While this type of training structure is almost universal in the running world, it is far less common in other endurance sports like cycling and triathlon. I have never understood why. Cyclists, runners, and triathletes all prosper under the same type of endurance phenotype: a robust cardiovascular engine. A strong cardiovascular engine that can process copious amounts of oxygen and deliver it to working muscles is a universal requirement for all endurance sports, even if the modalities are different. Logically, the training structure means to the cardiovascular end should be equally universal. Yet, this has historically not been the case. While many runners have used the mixed-intensity architecture I experienced in college, cyclists over the last twenty years have relied more on a “block” structure, focusing each month or training phase on one type of intensity (Tempo, for example). Triathletes took a different take entirely, using a hybrid of both to balance development across the three disciplines. Examples of mixed intensity periodization and block style periodization are shown below. Each contain about the same amount of training per week as well as the same number of interval workouts. The only wrinkle between the two is the type of specific interval work that is being done.

Figure 1- An example of mixed-intensity periodization: a way of organizing training where an athlete does workouts at a few or several different intensities during the week.

Figure 2- Block intensity periodization: a way of organizing training where an athlete does workouts at similar intensities during the week.

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So, which of these strategies will give you more bang for your training buck? Advocates for a mixed-intensity periodization commonly boil it down to a “use it or lose it” philosophy—meaning if you don’t stress your physiology in any one specific area (i.e., RunningIntervals that predominately stress VO₂ max) for as little as a few weeks, you will lose your hard-earned fitness across that specific piece of your physiological spectrum. Advocates for block-style architecture point to the fact that because you are concentrating the physiologic stress in one area, the adaptation is likely to be greater.

As there are advocates on both sides, let’s turn to the research to gain a little more clarity. On the whole, research slightly favors block-style architecture in both laboratory and field settings for sports such as cycling, kayaking, and cross-country skiing.  In 2010, a study performed by García-Pallarés out of the University of Murica pitted two groups of world class kayakers against each other, one utilizing a block style periodization and the other a traditional periodization. Although both groups gained a similar amount in VO2 max and VO2 at VT2 (a marker for lactate threshold) the block periodization group did so with 120 hours and 10 fewer weeks of training, indicating that block periodization might be a more efficient form of training. Hitting a little closer to home, in 2019 Norwegian researchers Mølmen, Øfsteng and Rønnestad performed a systematic review and meta-analysis comparing traditional endurance training to block training. They found that while advantages to improvements in VO2max were relatively small in block periodization compared to traditional periodization, those advantages grew under threshold intensity and for real world performance. As the authors note, although many of the block periodization vs. traditional periodization studies have moderate to low methodical quality (low subject count, lack of control, etc.), it’s difficult to find studies that show superior adaptations with traditional periodization and even more difficult to find studies where traditional periodization outperforms block periodization.

For athletes I work with, I will generally favor a block-style training structure for the majority of the year. In particular, for athletes that have seen stagnation for several months, or for athletes who are time crunched (remember the study on kayakers I referenced earlier), I find that athletes react and adapt better to focusing on the same intensity for weeks at a time as opposed to using a multitude of intensities every week. In addition, most ultramarathon races are performed in a very narrow range of intensities, and therefore it behooves an athlete to maximize development across that specific range, even if it is at the expense of some other area of physiology. In other words, you should be OK with the “lose it” criticism levied at the mixed-intensity philosophy because what you are losing is not deterministic in ultrarunning, so long as your long-range plan is structured correctly. Regardless of if you are new to ultrarunning or an experienced veteran, block style periodization can give you a boost.