Research · Programming

Linear, Undulating, or Block Periodization? What the Comparative Research Actually Shows

By Muhammad Dzulhisham · MSc Sports Coaching, NSCA-CSCS

Ask three coaches which periodization model is best and you'll usually get three confident, contradictory answers — and increasingly, a fourth opinion that periodization itself is overrated. Before taking a side, it's worth checking what happens when researchers actually put these models head-to-head, in the same athletes, under controlled conditions. The answer isn't the clean verdict either camp expects.

Linear vs. undulating: the largest comparison to date

A 2026 systematic review and meta-analysis in Frontiers in Public Health pooled 29 studies (704 total participants) comparing linear periodization (LP — load and volume change gradually over the whole program) against undulating periodization (UP — load and volume vary session-to-session or week-to-week).¹ This is the largest head-to-head comparison run on the question, and for the outcome most people actually care about — strength — the result is about as close to a tie as meta-analysis reporting gets:

Both confidence intervals cross zero, which is the statistical way of saying: no detectable difference. Explosive power and sprint speed showed the same pattern — no significant edge for either model. The one place a real difference showed up was body composition in a specific population: UP was better for short-term fat loss and reducing insulin resistance in men, while LP was more effective for long-term weight loss. For an athlete or general client training for strength or power, though, the headline finding holds: which of these two models you pick is not, on the current evidence, a strength-decisive choice.

Block periodization tells a more complicated story

Block periodization — concentrating training on one narrow quality (say, pure strength) for a dedicated block before shifting focus — is a different comparison, and the evidence splits by sport type in a way that's easy to miss if you only read the summary.

For endurance athletes, a 2019 systematic review and meta-analysis in the Open Access Journal of Sports Medicine found block periodization produced moderate-to-large favorable effects on VO2max and maximal power output compared to traditional periodization.² That sounds like a clear win — but the review's own authors flagged a real caveat: the studies feeding that result were generally small, with methodological quality low enough that the finding should be treated with caution rather than as settled.

For strength and power athletes, the picture is narrower still. A controlled trial in the Journal of Strength and Conditioning Research put 24 trained men through 15 weeks of either block or traditional periodization, matched for exercises, sessions per week, and total volume.³ Block periodization produced a real upper-body power advantage — a higher likelihood of increasing the force-power curve and shifting the load at peak power output in the bench press. But lower-body strength, jump power, and body composition showed no meaningful difference between the two groups.

The question "which periodization model is best" is mostly the wrong question. The evidence says the model matters far less than whether the program is actually progressed, monitored, and matched to the athlete in front of you.

What this means for choosing — or building — a program

None of this says periodization doesn't matter, or that any structure works as well as any other. It says the specific linear-vs-undulating debate that dominates a lot of coaching content is, for straightforward strength development, close to a non-issue — the 29-study comparison found essentially no difference between them. Block periodization has a real, more sport-specific case: promising for endurance athletes (with a caveat about study quality), and narrowly useful for upper-body power in trained lifters, without a demonstrated edge for general lower-body strength.

The practical implication is that a program's label is a much weaker signal of its quality than most marketing built around periodization terminology implies. What the research keeps pointing back to instead is the unglamorous stuff: whether load and volume are actually progressed over time, whether the plan accounts for the athlete's training age and current capacity, and whether it's built around what that specific person's goal actually requires — a testing-first starting point, not a periodization label borrowed from whichever model is trending this year.