Block Periodisation vs Traditional Build: Does the Structure of Your Winter Matter?

Every winter, triathletes face the same planning question. Do you build steadily, with a bit of everything every week, or do you focus: a fortnight of swim intensity, a bike-heavy block, a run block before spring? Block periodisation, the idea that concentrated blocks beat a mixed diet of training, has a following among coaches and a few impressive-looking trials behind it.

This article covers what block and traditional periodisation are, what the trials in cyclists and skiers actually found, why a later trial and a meta-analysis took some of the shine off, who was studied, and how the evidence applies to a triathlete planning a winter around three sports, a job and limited recovery.

Two ways to organise training

Traditional periodisation

Traditional, or mixed, periodisation develops several qualities at once. A typical week might include one or two interval sessions, a tempo session and several easy sessions, with the balance shifting gradually over months from general to specific work. Most triathlon plans follow some version of this.

Block periodisation

In a 2010 review in Sports Medicine, Issurin described block periodisation as sequencing specialised training cycles, or blocks, each with highly concentrated workloads aimed at a small number of target abilities. Instead of developing many qualities at once, block periodisation develops them one after another.

Issurin argued that traditional mixed training had four limitations:

• Conflicting responses from training many abilities at once.
• Excessive fatigue from prolonged multi-targeted training.
• Insufficient stimulus from the medium- and low-intensity loads typical of mixed training.
• Difficulty producing several peaks in a season.

In endurance research, "block periodisation" usually means something narrower: concentrating high-intensity interval sessions into one week, then dropping to one interval session a week for the following weeks, with the same total number of hard sessions as a traditional plan.

How much evidence was there to begin with?

In 2012, Kiely questioned the foundations of periodisation in the International Journal of Sports Physiology and Performance. He argued that models which look different on the surface share historical assumptions that are no longer scientifically justified, and that individual responses to training vary so widely that rigid, rule-based plans struggle. He didn't argue for abandoning planning, but for flexible, responsive systems. That's a useful lens for what follows: the question isn't which model is correct, but whether either has a measurable advantage.

The trials that made the case

Four weeks in trained cyclists

The most cited study is by Rønnestad, Hansen and Ellefsen in the Scandinavian Journal of Medicine and Science in Sports (published online 2012, in print 2014). Trained male cyclists were split into two groups with similar total volumes of high- and low-intensity training over four weeks:

• Block group (n = 10): five high-intensity interval sessions in week 1, then one per week for three weeks, with the rest of the training at low intensity.
• Traditional group (n = 9): two interval sessions every week, spread among low-intensity sessions.

The results:

• The block group improved VO2max by 4.6%, peak power by 2.1% and power at a blood lactate of 2 mmol/L by 10%.
• The traditional group showed no significant changes.
• The block group's VO2max improvement was significantly greater than the traditional group's.

Twelve weeks in well-trained cyclists

A follow-up by Rønnestad and colleagues in the same journal ran over a 12-week preparation period in well-trained male cyclists.

• Block group (n = 8): five interval sessions in every fourth week, then one per week for three weeks.
• Traditional group (n = 7): one interval session every week, 12 in total.

The block group increased VO2max by 8.8%, against 3.7% in the traditional group. Power at 2 mmol/L tended to improve more (22% versus 10%, not quite statistically significant), and the authors reported moderate effect sizes (0.62 to 1.12) favouring block periodisation for several measures, including mean power in a 40-minute all-out test.

These are encouraging results, but look at the numbers in each group: 10 and 9, then 8 and 7. With samples this small, a couple of strong responders can shift the averages.

Reading the early trials critically

Three features of these trials are worth keeping in mind before applying them:

• The traditional groups were fairly static. In the 12-week trial, the traditional group did exactly one interval session every week. A plan that never changes its stimulus is not the strongest comparison.
• Short trials favour novelty. A sudden week of five interval sessions is a big change from a cyclist's usual routine. Inference: some of the benefit may come from the shock of a new stimulus, which could fade if blocks were repeated all season.
• Physiological markers aren't race results. VO2max and power at a lactate threshold are useful indicators, but the 4-week trial's main reported outcomes were physiological rather than a race-like test, and the 12-week trial's performance advantage was a moderate effect size in 15 riders.

None of this means the findings are wrong. It means they're a starting point that needed replicating in larger, better-controlled studies, which is what happened next.

What the meta-analysis found

In 2019, Mølmen, Øfsteng and Rønnestad pooled the evidence in a systematic review and meta-analysis in the Open Access Journal of Sports Medicine. They found 20 studies published between 1993 and 2019, but only six parallel-group trials, with 107 participants, could be pooled. Participants were trained or well-trained athletes, mainly cyclists, cross-country skiers, ice hockey players and alpine skiers. Four of the six pooled trials included only men.

• VO2max: a small advantage for block periodisation (standardised mean difference 0.40, 95% CI 0.02 to 0.79).
• Maximal power output: a small advantage (standardised mean difference 0.28, 95% CI 0.01 to 0.54).
• Prediction intervals for both crossed zero, meaning a future study could plausibly find no benefit.
• Endurance performance itself couldn't be pooled because there were too few studies and the tests varied.

The quality of the evidence was low to moderate: the parallel-group studies averaged 3.7 out of 10 on the PEDro quality scale, with common problems including unblinded testers and unclear randomisation. The authors called block periodisation an adequate alternative to traditional periodisation, with small but favourable effects, and noted that it's hard to separate the effect of the block structure from the effect of simply changing the training. Several of the included trials came from the same Norwegian research group as the review's authors.

The trial that found no difference

In 2022, Almquist and colleagues published a larger and more carefully controlled trial in Frontiers in Physiology, with researchers from the same Norwegian network. 30 trained cyclists (26 men and 4 women) with a baseline VO2peak of about 58 ml/kg/min trained for 12 weeks from January to March.

• Both groups did the same number of high-, moderate- and low-intensity sessions, with matched training load and about 92% adherence.
• The block group organised each four-week cycle into a week of moderate-intensity sessions, a week of low-intensity training and a week of four high-intensity sessions, then a recovery week.
• The traditional group alternated intensities within weeks, with the number of intervals increasing progressively.

The result:

• Time-trial gains didn't differ between groups. Pooled across both, 5-minute time-trial power rose about 9% and 40-minute power about 8%.
• Maximal power rose about 6% and power at 4 mmol/L about 10%, again with no group difference.
• Some physiological responses differed: the traditional group had larger increases in capillaries, and the block group a larger increase in red blood cell volume.
• The analysed samples were smaller than those recruited: performance comparisons included 11 riders in the block group and 15 in the traditional group, after exclusions for low compliance and one dropout.

The authors concluded that block periodisation was not superior to a "best practice" traditional plan with progressively increasing load, though it might be useful as a short-term overload tool. Inference: one plausible reading of the earlier positive trials is that their traditional groups weren't progressive enough, rather than that blocks have a unique benefit.

The world's best skier did both

A 2019 case study by Solli, Tønnessen and Sandbakk in Frontiers in Physiology compared two seasons of training by the world's most decorated female cross-country skier. In one season she used block periodisation, with seven high-intensity blocks of 7 to 11 days; in the other, a traditional progressive approach. Total training load didn't differ significantly between seasons. The block season had fewer hours (15 versus 18 a week), less low-intensity training, far fewer moderate-intensity sessions (13 versus 38 a year) and more high-intensity sessions (157 versus 77). The paper's title sums it up: two different paths to success.

One elite athlete is not evidence for anyone else. But it illustrates the broader point: at the highest level, very different structures can work when total load and recovery are well managed.

Who was studied

• Sport: cyclists dominate, with skiers and team-sport athletes. No trial has included triathletes.
• Sex: most trials were in men. The 2022 cyclist trial included four women among 30 participants.
• Training level: trained to well-trained athletes, often with relatively high training volumes and fewer competing demands than age-group triathletes.
• Duration: most trials lasted 12 weeks or less, usually in pre-season. Effects over a full season are unknown.

What it means for a triathlete

Inference: triathlon complicates the picture. A cyclist doing five interval sessions in a week can rest everything else. A triathlete doing five bike interval sessions still has to swim and run, often around work and family. The block studies concentrated one sport's intensity in an otherwise easy week; copying that across three sports at once would be a very large overload.

The evidence above suggests:

1. Structure is a second-order decision. The largest, best-controlled trial found no performance difference when total load was matched. Getting total load, consistency and recovery right matters more.
2. Short blocks can be a useful tool. A concentrated week of one sport's intensity, followed by easier weeks, is a reasonable way to refresh a stalled sport or vary training. TriForward's "Fixing the Weak Leg" looks at a longer swim-focused version of this idea.
3. Recovery weeks are part of the method. Both block designs in the cyclist trials followed concentrated weeks with lighter ones. Skipping them turns a block into accumulated fatigue. TriForward's "The Spring Training Camp" covers what happens when an overload week goes too far.
4. Progression matters in either model. The traditional group in the 2022 trial progressed its interval volume week by week, and it did as well as the block group.
5. How you spread intensity across a normal week is a related but separate question, covered in TriForward's "Polarised, Pyramidal or Threshold: How to Spread Your Winter Intensity".

A triathlon scenario

The following example is illustrative, not drawn from a study. A 47-year-old triathlete training about 9 hours a week finds his bike fitness has stalled after two winters of the same plan, while his swim and run are progressing.

A block-based option might look like this:

• Week 1: four bike interval sessions, with swims and runs kept short and easy.
• Weeks 2 and 3: one bike interval session a week, with normal swim and run training resumed.
• Week 4: a lighter recovery week across all three sports.

A traditional option would spread the same number of bike interval sessions across the four weeks, progressing the interval volume each week. Based on the 2022 trial, he could reasonably expect similar gains from either. If the change of structure helps him stay motivated or breaks a stale routine, that's a legitimate reason to choose it.

Common mistakes

• Treating block periodisation as proven superior. The meta-analysis found small effects with wide uncertainty, and the largest matched trial found none.
• Stacking blocks across all three sports at once. The trials concentrated one sport's intensity, not everything.
• Skipping the easy weeks. Concentrated loading only works with recovery after it.
• Comparing a block plan with a non-progressive traditional plan. A traditional build that never progresses will look worse than almost anything.
• Copying elite structures. A world-class skier's season says little about an age-grouper's winter.
• Ignoring warning signs during a block. Unusual fatigue, poor sleep and illness are signs to back off. TriForward's "Reading the Trend, Not the Number" covers using heart rate variability as one check.

What we don't know

• Whether block periodisation helps triathletes training across three sports.
• Effects in women and masters athletes, who are barely represented.
• Long-term effects, across a full season or several years.
• Whether benefits come from the block structure or from novelty, since changing any training pattern may produce a short-term boost.
• The best block length and recovery for age-group athletes with limited recovery capacity.

References

• Issurin VB. New horizons for the methodology and physiology of training periodization. Sports Medicine, 2010;40(3):189–206. doi:10.2165/11319770-000000000-00000
• Kiely J. Periodization paradigms in the 21st century: evidence-led or tradition-driven? International Journal of Sports Physiology and Performance, 2012;7(3):242–250. doi:10.1123/ijspp.7.3.242
• Rønnestad BR, Hansen J, Ellefsen S. Block periodization of high-intensity aerobic intervals provides superior training effects in trained cyclists. Scandinavian Journal of Medicine and Science in Sports, 2014;24(1):34–42. doi:10.1111/j.1600-0838.2012.01485.x
• Rønnestad BR, Ellefsen S, Nygaard H, Zacharoff EE, Vikmoen O, Hansen J, Hallén J. Effects of 12 weeks of block periodization on performance and performance indices in well-trained cyclists. Scandinavian Journal of Medicine and Science in Sports, 2014;24(2):327–335. doi:10.1111/sms.12016
• Mølmen KS, Øfsteng SJ, Rønnestad BR. Block periodization of endurance training: a systematic review and meta-analysis. Open Access Journal of Sports Medicine, 2019;10:145–160. doi:10.2147/OAJSM.S180408
• Almquist NW, Eriksen HB, Wilhelmsen M, Hamarsland H, Ing S, Ellefsen S, Sandbakk Ø, Rønnestad BR, Skovereng K. No differences between 12 weeks of block- vs. traditional-periodized training in performance adaptations in trained cyclists. Frontiers in Physiology, 2022;13:837634. doi:10.3389/fphys.2022.837634
• Solli GS, Tønnessen E, Sandbakk Ø. Block vs. traditional periodization of HIT: two different paths to success for the world's best cross-country skier. Frontiers in Physiology, 2019;10:375. doi:10.3389/fphys.2019.00375