REF-1219 · Hickson & Rosenkoetter, 1981 · Medicine & Science in Sports & Exercise · Paper · PubMed

How little can I train and keep my VO2max?

In 12 study-trained young adults, 2 sessions a week at the same intensity and length held it for 15 weeks; only VO2max was measured, not endurance or race fitness.

Blimited evidenceMeasured on non-athletes and recreational people

Hickson and Rosenkoetter asked how often people need to train to keep a training-induced rise in VO2max. Twelve subjects (average age 23) cycled and ran 40 min a day, 6 days a week, for 10 weeks; VO2max rose on average 25% when measured on the bicycle and 20% on the treadmill.

They then trained 4 or 2 days a week for 15 more weeks, with intensity and session duration the same as in week 10. VO2max measured every 5 weeks stayed essentially at the trained level in both groups.

The authors conclude that more exercise is needed to increase VO2max than to maintain it in young adults doing high-intensity exercise, and that VO2max can be held for at least 15 weeks by training at high intensity 2 or 4 days a week.

Our reading: the source of the "two sessions a week hold endurance for 15 weeks" figure that reviews carry (REF-587); what it held was VO2max, in study-trained young adults, with intensity and duration protected — and its companions show that cutting session length by two-thirds (to 13 min) cost long endurance while a one-third cut (to 26 min) held it (REF-1220) and cutting intensity costs VO2max (REF-951).

Protocol

Participants: 12 subjects, average age 23 years; the record's MeSH terms list men and women (numbers not given); prior training status not given in the abstract.
Training phase: endurance exercise of bicycling and running, 40 min a day, 6 days a week, for 10 weeks; the abstract describes it as high-intensity exercise but gives no session content or intensity.
Reduced-frequency phase: 15 weeks at 4 days a week or 2 days a week; intensity and duration the same as in the tenth week of training. Group sizes and how subjects were assigned are not given in the abstract.
Measurements: VO2max on a bicycle and on a treadmill before training, after 10 weeks, and at 5-week intervals during reduced training.
Funding: US Public Health Service (NIH) grant and non-US-government support (record's grant list and publication types); conflicts not stated.

Key Results

PhaseFrequencyVO2max
Weeks 1-106 days a week, 40 min+25% (bicycle test), +20% (treadmill test) (average)
Weeks 11-254 days a week, same intensity and durationremained essentially at the trained level at each 5-week test
Weeks 11-252 days a week, same intensity and durationremained essentially at the trained level at each 5-week test
Not given in the abstract: group sizes, the VO2max values and any small changes behind "essentially the same", statistics, and any outcome other than VO2max (no endurance-time, threshold or performance measure is reported here).
Authors' conclusion: "it is possible to maintain the increased VO2max for at least 15 wk by training at high intensity for 2 d/wk or 4 d/wk."

Mechanisms

Measured: VO2max only; no cardiac, blood or muscle measure is reported in the abstract.
Authors' interpretation: the exercise needed to raise VO2max is more than the exercise needed to keep it.
Inference: each maintenance session kept the full intensity and the full 40 min, so a 2-day week still delivered the hardest part of the stimulus twice; the companion studies show what goes when the other two levers are cut — duration (long endurance fell at 13 min a day while VO2max held, REF-1220) and intensity (VO2max not held, long endurance −21% and −30%, REF-951).Read together: intensity protects VO2max and long endurance; a two-thirds cut in session length cost long endurance; whether a two-thirds cut in frequency (to 2 days) costs long endurance is unknown, because this study reports VO2max only.

Practical Application

How little can I train and keep my VO2max? In 12 study-trained young adults, 2 sessions a week at the same intensity and length held it for 15 weeks; only VO2max was measured, not endurance or race fitness.
When life squeezes the week, cut days before you cut the hard part: keep the intensity and the length of the sessions you do and drop the number of days; this is the order of cuts the three Hickson studies support, read together (our reading; REF-951 for intensity, REF-1220 for duration).
Two a week was the lowest frequency tested here: "one session every 7-10 days" maintenance figures come from other studies (REF-166, transition period in well-trained cyclists; REF-1133, detraining review); this study does not test them.
For an athlete, hold more than the minimum: the subjects had trained for only 10 weeks and were tested on VO2max alone; a long-trained athlete protecting race fitness, long endurance or threshold power should expect to need more than two short weeks (inference; REF-587 states athlete data are insufficient).
Fits the base's maintenance practice: a non-target quality kept on a maintenance dose with its intensity intact (SYNTH-76, REF-1077 per-session doses, C) now has its frequency evidence here, in untrained subjects.

Limitations

Small: 12 subjects split into two groups of unreported size; allocation not described in the abstract.
No full-training control is described, so it cannot show how much of the 15-week value would have risen further at 6 days a week.
Study-trained young adults: the gains were 10 weeks old; whether long-held fitness behaves the same is not tested.
VO2max only: endurance capacity, threshold, economy and race performance were not reported in the abstract; "maintained" here means VO2max.
"Essentially the same": no values or statistics are given in the abstract.
Written from the abstract and record metadata (full text not read).
How this entry was checked and changed
Why this level

small two-group study, n = 12, no full-training control described; read from the abstract (closed access, 1981; no open copy via Europe PMC or OpenAlex). Group sizes, allocation, VO2max values and any endurance or performance outcome are not given in the abstract