REF-946 · Mølmen et al., 2019 · Open Access Journal of Sports Medicine, Vol. 10, pp. 145-160 · Paper · PubMed · Free full text

Block periodization of endurance training - a systematic review and meta-analysis

A-fairly strong evidenceMeasured on trained to elite athletesWritten before October 2026, being re-checked

Block periodization (BP) has been proposed as an alternative to traditional (TRAD) organisation of the annual plan for endurance athletes. This is, to the authors' knowledge, the first meta-analysis of BP of endurance training on endurance performance and its determinants in trained to well-trained athletes.

PubMed, SPORTdiscus and Web of Science were searched from inception to August 2019; of 2905 studies screened, 20 records were eligible and six were pooled for maximal oxygen uptake (VO2max) and maximal power output (Wmax) in an incremental test. The meta-analyses showed small favourable effects for BP over TRAD in VO2max and Wmax.

For endurance performance and workload at exercise thresholds, which were reviewed without pooling, BP generally showed moderate to large effect sizes over TRAD. The authors call BP an adequate alternative to TRAD and ask for caution because the studies are small and of generally low quality.

Participants

Trained to well-trained athletes across 20 eligible records; six studies pooled. Participant numbers are not given in the abstract.

Protocol

Databases: PubMed, SPORTdiscus, Web of Science, inception to August 2019.
Inclusion: a block-periodized endurance training intervention; one-, two- or multiple-group, crossover or case-study design; at least one key endurance variable before and after.
2905 studies screened, 20 records eligible; quality by PEDro scale.
Meta-analysis (six studies) for VO2max and Wmax; other performance measures systematically reviewed because of fewer studies and heterogeneous measurements.

Key Results

VO2max: standardized mean difference 0.40 (95% CI=0.02, 0.79) in favour of BP over TRAD.
Wmax: standardized mean difference 0.28 (95% CI=0.01, 0.54) in favour of BP over TRAD.
Endurance performance and workload at exercise thresholds: BP generally showed moderate- to large-effect sizes compared with TRAD (not pooled).
Methodological quality generally low: mean PEDro score =3.7/10.

Practical Application

"Is block periodization better than spreading the hard sessions evenly?" Pooling six studies in trained to well-trained athletes, block periodization gave small advantages over traditional organisation in VO2max (SMD 0.40, 95% CI 0.02 to 0.79) and Wmax (SMD 0.28, 95% CI 0.01 to 0.54) — from small studies of low quality (mean PEDro 3.7/10). Block is a legitimate option with a small, uncertain edge, not a proven winner.
Both intervals start just above zero; one more null study could remove the effect. Do not promise a gain from switching to blocks.
Not from this paper: the trial design behind most of the block evidence is in REF-136, and a later review in trained cyclists found no outcome basis for choosing (REF-103).
Not from this paper; the base's own practice: a block redistributes the hard sessions the athlete already tolerates and does not add to them; where blocks sit in the season is in SYNTH-76.

Limitations

Only six studies pooled; small samples; mean PEDro score =3.7/10.
Lower bounds of both confidence intervals are close to zero.
Designs included one-group and case studies in the wider review; performance outcomes were not pooled.
Intervention lengths and block formats are not described in the abstract.
The authors are from the group that ran several of the block trials.
Written from the abstract and record metadata only (full text not read).
How this entry was checked and changed
Why this level

meta-analysis of small studies with generally low methodological quality (mean PEDro score =3.7/10); confidence intervals reach close to zero