A Fresh Look at Block Periodization

Many moons ago, I wrote a post for this blog that bore the title, “The Human Body Is Not a Smartphone.” In it I argued that endurance training methods cannot advance indefinitely in the way that technologies such as smartphones can. “Once the best ways to train and fuel the human body for distance racing have been discovered,” I wrote, “it is impossible to improve upon them further until and unless the human body changes enough for different methods to become optimal.”

Even as I composed these lines, I knew they weren’t completely true. The idea that, given enough time, the optimization of endurance training methods is more or less inevitable is based on the notion that endurance sport operates as a self-organizing system. “A what?” you say. A self-organizing system.

Data scientist David Green of Monash University defines self-organization as “the emergence of pattern and order in a system by internal processes, rather than external constraints or forces.” Natural evolution is the best example of a self-organizing system, but computer scientists and engineers are able to create artificial self-organizing systems that are capable of evolving optimal solutions to real-world problems such as managing runway traffic at airports. If you place a graph representing such an evolutionary process next to a graph representing improvement in, say, the men’s marathon world record from 1896 to today, the two curves will appear uncannily similar in shape—a compelling illustration of endurance sport’s self-organizing behavior.

There are important differences between human endurance sport and computer models of airport throughput, however. Most notably, endurance sport is a social system nested inside the larger societal system, and as such it is subject to certain braking forces on its evolution that manmade self-organizing systems are not. Tradition is one such factor. In my experience, the top endurance coaches don’t put as much effort into innovating as they might, and I think that’s simply because, as human beings, top endurance coaches are deferential to “the way things are done” in the sport, no different than how teachers are deferential to the traditions of the institution where they teach. Consequently, opportunities to do things a little better sometimes wait a little longer to be discovered than they do in tech.

Which brings us to the topic of this article. The innovation known as block periodization originated in the weightlifting realm, where the practice is widespread. In the endurance realm, the term carries a slightly different meaning and the practice is not as widespread. As it applies to endurance sports, block periodization entails separating the volume and intensity elements of training. For example, a runner might do a block of three high-intensity workouts one week and a block of six longer low-intensity workouts the next week.

The developers of block periodization saw it as a way to make training harder without making it more stressful. They presumed that elite athletes were already training as hard as they could in the traditional way, where high-volume, low-intensity interval training and high-intensity interval training are mixed. It seemed plausible that by separating these two different types of training, athletes could do more of both without necessarily doing either in excess. During high-intensity training weeks, athletes would not be limited by fatigue induced by long workouts at low intensity, and during volume weeks, athletes would not be limited by fatigue induced by high-intensity intervals workouts.

Among the leading scientific investigators of block periodization in endurance athletes is Bent Rønnestad of Inland Norway University. In a 2019 meta-analysis of his and others’ work in this area, Rønnestad and colleagues concluded, “Block periodization is an adequate, alternative training strategy to traditional periodization as evidenced by superior training effects on VO2max and [maximal power output] in athletes. The reviewed studies show promising effects for BP of endurance training; however, these results must be considered with some caution due to small studies with generally low methodological quality.”

The most recent study of the effects of block periodization was conducted by Polish researchers and published in the International Journal of Environmental Research and Public Health last month. Twenty competitive mountain bikers were separated into two groups. For eight weeks, members of one group followed a traditional periodization model where each week included a mix of low-intensity riding, high-intensity interval work, and sprint interval training, while the second group followed a block periodization model where 17-day blocks of low-intensity riding were alternated with 11-day blocks of HIIT and sprint interval sessions.


Both groups underwent physiological and performance testing before and after the eight-week training period. Improvements were about equal in the two groups in all measures except VO2max, where the traditional periodization group experienced bigger gains, going from 3.66 to 4.2 L∙min−1 compared to 3.75 to 4.0 L∙min−1 in the block periodization group.

Where does this leave us? For better or worse, training innovations that are disruptive to existing best practices need to have a better story to tell than “possibly slightly superior in some metrics according to some but not all studies” if they are to overcome the inertia of tradition. I stand ready to be an early adopter of the next such innovation that comes along, but block periodization probably ain’t it.

You have races.

We have plans.



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