What is best practice for training intensity and duration distribution in endurance athletes?
Scope
Widely cited review of how successful endurance athletes distribute training intensity, duration and frequency. It draws on descriptive studies of nationally and internationally competitive athletes and on intensification studies in already well-trained athletes (the sports covered — running, skiing, rowing, cycling, triathlon — are from the full text; not checked against the abstract).
Key Findings (principles)
1. Elite TID converges on ~80/20 by sessions
Descriptive studies of national/international athletes training 10 to 13 times per week converge on about 80% of training sessions at low intensity (about 2 mM blood lactate) and about 20% dominated by high-intensity work such as interval training at approximately 90% VO2max.
The unit in the abstract is the session, not minutes: 80% of sessions, not 80% of time.
2. Self-organisation toward high volume with careful HIT
Endurance athletes appear to self-organise toward a high-volume approach, with high-intensity training applied carefully throughout the training cycle rather than concentrated.
3. More HIT is not better in the already well-trained
Intensification studies in already well-trained athletes give no convincing evidence that a greater emphasis on high-intensity interval training produces long-term performance gains.
4. Why the pattern may work (the author's hypothesis)
Abundant low-intensity, long-duration training combined with fewer, highly intensive bouts may be complementary: adaptive signalling and technical mastery at an acceptable level of stress.
The abstract describes low and high intensity; it does not quantify a threshold/"tempo" share. That elite athletes spend little time at threshold is in the full text (full text; not checked against the abstract).
Practical Application
Descriptive data on nationally and internationally competitive endurance athletes training 10 to 13 sessions a week converge on about 80% of sessions at low intensity (about 2 mM lactate) and about 20% dominated by high-intensity work at approximately 90% VO2max; intensification studies in already well-trained athletes show no convincing long-term gain from more HIT. The week is anchored by many easy sessions and a minority of genuinely hard ones — count sessions, not hours.
Adding intensity is not the lever once an athlete is already well trained: the review found no convincing evidence that a greater HIT emphasis pays off long-term in that population. Consistency of the easy volume is what makes the hard sessions repeatable.
Not from this paper: how many hard sessions per week that 20% amounts to in practice is documented from coaches in Sandbakk 2025 REF-138 (2-3 key days per week).
Limitations
Narrative review: the 80/20 figure is a convergence of descriptive studies of elite athletes, not an experimental prescription, and the abstract gives it by session count, not by time.
The "no convincing evidence for more HIT" statement is about already well-trained athletes; it says nothing about beginners.
Built mainly on descriptive and observational data from national and international athletes training 10–13 sessions a week: it describes what successful athletes DO, and the controlled evidence behind the distribution is thinner.
The 80/20 split counts sessions, not minutes — a session-goal count and a time-in-zone count give different pictures of the same week.
It does not scale down directly to athletes on a few hours a week (SYNTH-26).
How this entry was checked and changed
Why this level
regraded 2026-09-27 from A+: narrative review from the leading TID group; no systematic method or meta-analysis
Content correction 2026-09-27
"HIT frequency 2-3/week; >3/week no benefit; >20% HIT does not improve performance" -> not in the abstract (it says only that a greater HIT emphasis shows no convincing long-term gain in well-trained athletes); numbers removed, the 2-3 key days pointed to REF-138 as "Not from this paper".
"~15-20% of sessions with significant work above threshold" -> abstract: about 20% of sessions dominated by high-intensity work.
Zone labels (Z1/Z3-Z5) and the "middle zone avoided" claim -> not in the abstract; kept only as labelled full-text content.
Tier 4-5 -> Tier 3-4 (nationally or internationally competitive); Level A+ -> B+ (narrative review) per KB-LEVEL-RUBRIC.
Cross-references to duplicate stubs repointed to their canonical entries (REF-085->REF-303, REF-093->REF-304); the stubs were emptied on 2026-09-27.
Cross-reference descriptions checked against the cited entries' current content; wrong years, wrong entries and claims the cited entry does not make were corrected.