Training periodization: models, research and practice

What training periodization means: three levels of planning

Periodization is the organization of training over time. Instead of making every week the same, you divide the season into blocks that build on each other and each have their own focus. Issurin (2010) describes the traditional form as splitting the whole season's program into smaller periods and training units.

There are usually three nested levels: the annual plan forms the macrocycle, which is divided into phases and mesocycles, and these in turn into microcycles (Lyakh et al., 2016). How long each cycle lasts is a convention and differs from author to author. The durations in the table are therefore guidelines, not rules.

Durations are conventions and vary from author to author.

Each level answers its own question. The macrocycle settles when the athlete should be in top shape and in which order the phases come. The mesocycle sets what takes priority over the next few weeks. The microcycle decides what is trained on which day and when to rest.

Issurin's block periodization: one focus after another

As an alternative, Issurin (2008, 2010) describes block periodization: a sequence of specialized training cycles, the blocks. Each block contains highly concentrated workloads aimed at as few target abilities as possible. Instead of training many things at once, you set your priorities one after another.

The basic unit is the mesocycle. In Issurin's model, three types follow each other: accumulation, transmutation and realization. As presented by Lyakh, Zając and Bujas (2011), such a phase of three mesocycles lasts 4 to 10 weeks. That means you can repeat it several times in a season, for example before several important competitions.

Residual training effects make this work: the effect of a block does not disappear as soon as the block ends. Issurin (2008) describes how the sequence of specialized mesocycle blocks makes use of these residual effects. The next block thus builds on the previous one, even if the ability trained before is no longer the main focus.

What the research says about training periodization

Several meta-analyses compare periodized with non-periodized strength training. Rhea and Alderman (2004) report an overall effect of ES 0.84 in favor of periodized programs and put the effect specific to training variation at ES 0.25. Williams et al. (2017) found ES 0.43 for maximal strength (1RM, the load for a single repetition) in favor of periodized training, with a 95% confidence interval (CI) of 0.27 to 0.58.

The CI shows how precisely a value is estimated: if it lies entirely above 0, the advantage is considered statistically solid. In Williams et al., undulating programs did better, and the effect was larger in untrained individuals. Across 35 volume-equated studies, Moesgaard et al. (2022) found ES 0.31 (CI 0.04–0.57) for maximal strength: a small advantage whose CI reaches almost down to 0. There was no difference for muscle growth (ES 0.13).

Afonso et al. (2019) urge caution: none of the 21 studies in two meta-analyses compared periodization with training that was varied but not periodized. For endurance, Mølmen et al. (2019) found slightly better values for block periodization in VO₂max (maximal oxygen uptake) and Wmax (maximal power), but in small, low-quality studies (PEDro scale, 3.7 out of 10 on average).

ES and SMD: standardized effect sizes, 0 means no difference. CI: confidence interval.

Kiely (2012) offers a more fundamental critique: periodization models share a deeply rooted cultural heritage, along with assumptions that can no longer be justified scientifically. He calls for training systems that respond sensitively to the athlete, while explicitly not rejecting periodization altogether. Kiely (2018) adds that periodization rests on Selye's stress research; since stress science has moved on, a reassessment is needed.

Others take the opposing view: Cunanan et al. (2018), whose title calls the general adaptation syndrome a foundation for the concept of periodization, and Stone et al. (2021), with a review of periodization and block periodization that, according to its title, focuses on strength-power training.

The bottom line: on average, periodized strength training produces slightly more maximal strength than non-periodized training, even at equal volume (Moesgaard et al., 2022). The studies do not clearly show which model is best. What is clear: planned variation and adjusting to the athlete's response matter (Harries et al., 2015; Kiely, 2012).