SYNTH-106 · Guide
Keeping what you built
Protect the intensity, cut the rest: in small trials over 12-15 weeks, strength held on one session a week, VO2max on two days a week or on sessions cut by up to two thirds but not on easier ones, and sprint on one weekly strength session; stopping costs VO2max within weeks and strength more slowly
The question it answers
"I have a busy month (exams, work, a new baby, the race season) — what is the least I can do and not lose it?" and "how fast do I lose it if I stop?"
Default (what to prescribe first)
Keep the intensity; cut volume and frequency. That is the review's overarching conclusion, that intensity 'seems' to be the key variable (REF-587, C+), and the Hickson trials point the same way: lowering the work rate lost VO2max and long endurance (REF-951, B); cutting to two days a week kept VO2max, the only measure taken (REF-1219, B); shortening sessions kept VO2max and ~5-min endurance, but 2-h endurance fell 10% at the two-thirds cut (REF-1220, B).Frequency has a floor: one strength session every two weeks lost strength (REF-1628, REF-1136, B).
Strength and muscle: one session a week with the usual exercises and loads (REF-1628, B; REF-1136, B); a ninth of the training dose held muscle size for 32 weeks at 20-35 years, not at 60-75 (REF-1622, B+; the abstract does not say what a ninth was in days and sets); the review's summary for younger people is one session and one set per exercise a week at the usual relative load (REF-587, C+).
VO2max: two sessions a week at the usual intensity and length (REF-1219, B: 6 → 2 days a week held VO2max 15 weeks in study-trained young adults; endurance was not measured); if minutes are the problem, shorten sessions rather than soften them (REF-1220, B: sessions cut to 26 or 13 min a day, still 6 days a week, held VO2max and ~5-min endurance, but 2-h endurance fell 10% at 13 min).In trained endurance athletes on reduced volume, at least one weekly moderate-to-high-intensity session held VO2max in the few studies that tested it, but in triathletes one weekly 35-min session at 95% HRmax still left time to exhaustion 21% lower (REF-1133, B+, single small studies).
Speed and sprint: keep one strength session a week at the preseason exercises, sets and RM loads (REF-1628, B, 7 professional footballers per group: sprint held for 12 weeks with it and fell with one every two weeks; jump height did not change in either group) and the short sprints or fast reps themselves in the remaining sessions (practice; no maintenance trial of sprint training alone is in the base).
Heat adaptation: two sessions a week of heated exercise to hyperthermia kept heart rate in the heat lower than none 8 weeks later in 24 trained men, and one a week was not clearly better than none (REF-1246, B-; sauna or hot water as the route is untested); without heat about 2.5% of the acquired heart-rate and core-temperature adaptation fades a day, in mostly fit young men in heat-stress tests (REF-1197, B+).
Decision
| Quality | Least that held it | Not enough | How long it was tested |
|---|---|---|---|
| Strength | 1 session a week (REF-1628, REF-1136) | 1 session every 2 weeks: held 6 weeks, then lost part (−4.4% 1RM by week 12, REF-1136); strength and sprint fell in footballers (REF-1628) | 12 weeks |
| Muscle size, younger adults | a third or a ninth of the training dose (REF-1622) | — | 32 weeks |
| Muscle size, older adults | not found: neither a third nor a ninth held it (REF-1622); the review suggests up to 2 sessions and 2-3 sets per exercise a week (REF-587, C+) | a ninth and a third (REF-1622) | 32 weeks |
| VO2max | 2 days a week, same intensity and length (REF-1219); sessions cut by ⅓ or ⅔ (REF-1220) | work rate cut by ⅓ or ⅔ (REF-951) | 15 weeks |
| Long endurance (2 h+) | sessions cut by a third (REF-1220) | sessions cut by two thirds (−10%, REF-1220); work rate cut by a third (−21%, REF-951) | 15 weeks |
| 40-m sprint | 1 strength session a week (REF-1628) | 1 every 2 weeks (REF-1628) | 12 weeks |
| Heat acclimation | 2 sessions a week of 60 min heated exercise to hyperthermia: heart rate in the heat 23 bpm below none, read by the authors as maintained (REF-1246, B-, 24 trained men) | none (about 2.5% of the acquired adaptation lost a day, REF-1197); 1 a week not clearly different from none (p = 0.112, REF-1246) | 8 weeks |
How to progress / periodise
Plan the maintenance block as a block. Name it, keep the key session's intensity, and set a date to come back up (the base's practice; how to come back up is SYNTH-36).
Expect strength to outlast VO2max if everything stops (PHYS-41, established for the order of the losses; REF-374, C+).After complete cessation, VO2max fell about 4-7% in 2-3 weeks and 10-20% by 5-8 weeks in trained endurance athletes (REF-1133, B+); strength gained in 16 weeks was largely kept through 32 weeks without training in one trial (REF-1622, B+), and cessation costs all parts of muscular performance more the longer it lasts, and more in people over 65 (REF-375, B+).
When NOT to use it / red flags
Turning every session easy to save energy: the one trial that cut intensity lost VO2max and 21-30% of long endurance (REF-951).
Maintenance as a long-term plan: these doses held qualities for 8-32 weeks in these trials (heat 8, strength and sprint 12, VO2max 15, muscle size in younger adults 32); beyond those periods they are not shown to hold, and only one result shows a gain (a third of the dose added fibre size in younger adults, REF-1622).
Illness or injury decide the break by their own rules (SYNTH-36); this guide is for a chosen reduction.
What the evidence does and does not show
Shows (small trials, mostly study-trained young adults): frequency and session length can fall a long way at the same intensity without losing VO2max for 15 weeks, and strength held for 12 weeks on one session a week but not on one every two weeks; 2-h endurance fell when sessions were cut by two thirds; cutting the work rate lost VO2max (REF-1219, REF-1220, REF-951, REF-1136, REF-1628).
Does not show: a maintenance dose for trained endurance athletes beyond single small studies; a maintenance trial of speed endurance or W′ (the base's REF-695, C+, a narrative review, reports speed-endurance training keeping oxidative capacity and 30 s-4 min performance on reduced volume); whether the same rules hold for women (most trials are men, or do not report the split, except REF-1136 in young women).
Evidence gaps
Few maintenance trials in trained athletes; most trained their own subjects for 10-16 weeks first.
No study in the base tests maintaining sprint or power by sprint training alone.
The longest maintenance period tested here is 32 weeks.
How this entry was checked and changed
Why this level
the maintenance doses rest on small reduced-training trials, all but REF-1136 read from abstracts with group sizes or methods missing and most in study-trained subjects (B: REF-1219, REF-1220, REF-951, REF-1628, REF-1136; B+: REF-1622, a randomised trial read from its abstract; B+: REF-1133, single small studies in endurance athletes; heat: REF-1246, B-, and REF-1197, B+), a meta-analysis of training cessation (REF-375, B+) and narrative reviews (REF-587, REF-374, C+); the doses held over 8 to 32 weeks, so the rules are not shown beyond that
Content correction 2026-11-06
2026-11-06: written after the editor asked what dose keeps endurance, speed and strength; the base held the trials (Hickson, REF-1136, REF-800) and Spiering's review without a guide that sets them side by side; REF-1622 and REF-1628 added the same day.