REF-1444 · Festa et al., 2020 · Frontiers in Sports and Active Living · Paper · PubMed · Free full text

Can a between-threshold week replace a polarized one on 3-4 h?

In 38 recreational runners over 8 weeks, no detectable difference, on less time (24.8 vs 29.9 h, matched load). Small, short, 2-km test; not proof of equality.

Main caveat: Per-protocol: runners with adherence under 96% were excluded; no intention-to-treat analysis.
moderate evidenceMeasured on recreational to trained athletes

Festa and colleagues (University of Verona) randomised recreational runners, who had run a half marathon the week before, to 8 weeks of a polarized plan (PET, prescribed 77/3/20 across zones 1, 2 and 3; four sessions a week: two hard, one moderate, one easy) or a "focused" plan (FOC, prescribed 40/50/10; three sessions a week of medium and long repetitions at moderate intensity).

Plans were balanced on TRIMP, with minutes weighted 1, 2 and 3 by zone. Completed distributions were 78/3.1/18.9 and 38.7/48.8/12.5; total time 29.9 ± 3.1 vs 24.8 ± 2.0 h.

Both groups improved speed at VO2max (3.2 vs 4.0%), at the first threshold (4.0 vs 3.2%), at the second (5.7 vs 3.4%), 2-km speed (3.5 vs 3.0%) and running economy (−5.3 vs −8.7%); VO2max did not change in either; no between-group difference was significant. The authors conclude the focused plan "obtains similar improvements" and saves 17% of training time.

Our reading: the most direct trial in the base of a between-threshold-heavy week in time-limited recreational athletes, and it qualifies the warning about the middle zone for this population (SYNTH-26; compare REF-094, B, and REF-303, A-, in better-trained athletes). Two cautions.

Equal TRIMP with zone 2 weighted double makes the focused plan shorter by design, so "saves 17%" is what was prescribed, not an outcome. And the plan still held 3.1 h of zone 3; it was not tempo alone.

Protocol

Participants: 43 recruited, more than 4 years of training (6.4 ± 1.6), 3.2 ± 0.5 h a week; n = 38 analysed, PET 15 men and 4 women (43.2 ± 8.4 y, VO2max 52.9 ± 8.1), FOC 16 men and 3 women (39.4 ± 8.5 y, VO2max 53.4 ± 8.3).
Losses: FOC 4 (2 excluded for adherence under 96%, 2 left for personal reasons), printed as 21%; PET 1 (personal reasons), printed as 5%. Both percentages fit a denominator of the 19 analysed (our arithmetic).
Training: 2 introductory weeks, then two 3-week microcycles in a 2:1 load pattern; no strength work. Time goals, not distance; heart rate recorded in every session; session RPE 0-100.
Tests (weeks 0 and 9): treadmill ramp for VO2max, ventilatory threshold (VT) and respiratory-compensation threshold (RCT); running economy at 1 km/h below marathon pace; hand-timed 2-km time trial on a track; estimated 1RM leg press; jumps.
Analysis: 2 × 2 mixed ANOVA with Bonferroni correction, 90% confidence limits, effect size d.
Funding and interests: no funding statement printed; authors declare no commercial or financial relationships.

Key Results

OutcomePET pre → postFOC pre → postBetween groups
Total time (h, 8 weeks)29.9 ± 3.124.8 ± 2.0different
TRIMP total (au)2464.0 ± 124.02558.2 ± 10.9not different (P > 0.05)
Completed zones 1/2/3 (%)78 / 3.1 / 18.938.7 / 48.8 / 12.5prescribed difference
Session RPE (0-100)60.9 ± 15.565.4 ± 14.6not tested in the text
VO2max (mL/kg/min)53.0 → 53.6 (ns)53.7 → 53.2 (ns)ns
Speed at VO2max (km/h)13.9 → 14.3 (3.2%)13.8 → 14.3 (4.0%)ns
Speed at VT (km/h)10.5 → 10.9 (4.0%)10.8 → 11.1 (3.2%)ns
Speed at RCT (km/h)12.1 → 12.8 (5.7%)12.4 → 12.8 (3.4%)ns
2-km average speed (km/h)13.8 → 14.3 (3.5%)13.9 → 14.3 (3.0%)ns
Running economy (mL/kg/km)226.3 → 214.3 (−5.3%)231.8 → 211.6 (−8.7%)ns
Numbers that do not add up: the Results text gives PET speed at VO2max as 12.9 before training where Table 3 gives 13.9; FOC zone 1 and zone 2 hours are 9.1 and 11.5 in the text and 9.6 and 12.1 in Table 2; Table 4's ± values are far smaller than Table 1's for the same variables (body mass 70.9 ± 2.5 vs 70.9 ± 10.1) and look like standard errors, though Tables 3 and 4 are not labelled differently.
Individual response: not reported; no SD of change.

Mechanisms

Measured: gains in submaximal and near-maximal speeds without a VO2max change on either plan.
Authors' interpretation: recreational runners have little overtraining risk at 3-5 h a week and tolerate time between the thresholds; the focused model "seems to better meet the needs" of time-limited athletes.
Inference: runners coming off a half marathon on about 3 h a week may improve on almost any structured plan, so a shared gain could mask a difference; a 2-km test says little about a half marathon or longer.

Practical Application

Can a between-threshold week replace a polarized one on 3-4 h? In 38 recreational runners over 8 weeks, no detectable difference, on less time (24.8 vs 29.9 h, matched load). Small, short, 2-km test; not proof of equality.
Time-limited recreational runner: planned running between the thresholds is a defensible option at this volume. The load behind it is not smaller; the same TRIMP arrived in fewer minutes and session RPE was not lower.
Do not read fatigue from the dropouts: four left the focused arm and one the polarized arm, but two of the four were exclusions for adherence and two personal reasons; the paper reports no injury or fatigue data. Not evidence for or against a higher cost.
Not from this paper; the base's own practice: for athletes on more hours keep the middle zone a tool (SYNTH-27, SYNTH-26).
What it does not show: that a between-threshold plan matches polarized in the well-trained, that VO2max responds, or any effect in cyclists or over a season. It tested a three-zone heart-rate plan, not any sweet-spot prescription.

Limitations

Per-protocol: runners with adherence under 96% were excluded; no intention-to-treat analysis.
Small and short; a null between arms, no power calculation printed, 8 weeks.
Time difference follows the design (TRIMP weights) and session counts differed (3 vs 4).
Outcome: 2-km hand-timed test; the authors note the lack of half-marathon or marathon outcomes.
Reporting slips in the text and tables, noted under Key Results.
Heart-rate zones can overstate time in higher zones through drift (our reading); not addressed in the paper.
Mostly men (31 of 38).
Funding: not printed; no commercial or financial conflict declared.
How this entry was checked and changed
Why this level

the rubric's band for a parallel RCT of 20-39; not raised or lowered, with these limits stated: analysis of those who stayed and adhered, no registration or power calculation printed, allocation concealment not described, and a null between arms that cannot show equivalence

Full text (checked 2026-10-30)
Forty-three recreational runners were recruited; mean training volume before the study was 3.2 ± 0.5 h per week (full text)
Dropout rate for the FOC group was 21% (two subjects was excluded from the analysis due to training program adherence <96%; two abandoned the experiment for personal reasons); dropout rate for the PET group was 5% (full text)
Total running time 29.9 ± 3.1 and 24.8 ± 2.0; total TRIMPs 2464.0 ± 124.0 and 2558.2 ± 10.9 (full text)
TTT % in zone 2: 3.1 ± 1.3 and 48.8 ± 12.8; TTT % in zone 3: 18.9 ± 4.6 and 12.5 ± 5.7 (full text)
TRIMP is computed by multiplying the accumulated time in each zone by an intensity weighted coefficient (1 for zone 1, 2 for zone 2 and 3 for zone 3) (full text)
No significant difference was found in the comparison between the groups in any investigated variable before and after training (full text)
Both groups significantly improved their velocity at V'O2max (3.2 and 4.0%), at VT (4.0 and 3.2%), RCT (5.7 and 3.4%), the average velocity in 2 Km performance (3.5 and 3.0%) and RE (−5.3 and −8.7%) (full text)
The authors declare that the research was conducted in the absence of any commercial or financial relationships (full text)