Minimum effective dose for strength and endurance

To keep what you've built, you need far less than it took to build it. In the studies Spiering and colleagues reviewed, strength and muscle size held for up to 32 weeks on one session a week and one set per exercise, and endurance held for up to 15 weeks on two sessions a week, as long as the intensity stayed the same.¹ Intensity is the one thing you can't cut. Load on the bar, pace or heart rate on the run.

That's the maintenance dose. Still gaining strength takes a bit more, and the numbers for that are below too.

Keeping strength#

Spiering's review is the cleanest summary of maintenance.¹ In younger adults, strength and muscle size held for up to 32 weeks with a single weekly session and one set per exercise, provided the relative load stayed where it had been. Older adults needed more to keep muscle size: up to two sessions a week and two to three sets per exercise.

Bickel's trial shows how forgiving strength is.² Seventy adults lifted three days a week for 16 weeks, then spent 32 weeks either stopping completely or training at a third or a ninth of the original dose. In the younger group (20 to 35), both reduced doses kept the muscle growth, and the one-third dose even added a little fibre size. Strength was mostly retained even by the group that stopped, with only a slight drop at the final test. Older adults (60 to 75) needed more weekly loading to keep their fibre size, though their strength held up well.

Two caveats. These people had trained for 16 weeks, not years. And 32 weeks is how long the studies ran, not a known limit.

For runners specifically, Schumann's 24-week trial is the useful one.³ Recreational runners trained 4 to 6 times a week. One group added two strength sessions a week straight after a run. The run-only group's leg press 1RM fell 5 percent. The group that lifted twice a week kept theirs.

Keeping the engine#

Endurance is held the same way, through intensity, but it needs a bit more frequency.¹ In general populations, endurance held for up to 15 weeks when sessions dropped to as few as two a week, or when volume dropped by a third to two thirds, down to 13 to 26 minutes a session, as long as exercise heart rate stayed the same. The review found too little data to make specific recommendations for athletes.

How long each quality held on a minimal dose

	Value (weeks)
Strength and size: 1 session, 1 set per exercise	32
Endurance: 2 sessions, or 33 to 66% less volume	15

Longest maintenance periods in the studies reviewed by Spiering et al. 2021 (abstract). Study durations, not known limits. Intensity was kept in both.

In real terms, if your usual run is 40 minutes, a third to two thirds less is about 13 to 27 minutes, which lines up with the 13 to 26 minute sessions in the review. Shorter is fine. Slower isn't.

So in practice, the engine needs at least two sessions a week at the intensity you were training at before. Two slow jogs in place of your usual pace don't count.

What fades first when you stop#

If you stop completely, the two halves don't fade at the same rate.

In the first four weeks without enough training, highly trained endurance athletes lose VO2max and blood volume fast, while strength declines are limited.⁴ The drop is more moderate in people who've only recently got fit. The same review lists the metabolic side: more reliance on carbohydrate during exercise, a lower lactate threshold, and fewer capillaries and oxidative enzymes in the muscle.

Strength does fade eventually. A meta-analysis of 103 studies on stopping resistance training found declines in every component: submaximal strength (SMD -0.62, 95% CI -0.80 to -0.45), maximal force (-0.46, -0.54 to -0.37) and maximal power (-0.20, -0.28 to -0.13).⁵ The longer the break, the bigger the drop. It was larger in people over 65, and for maximal force and power, larger in inactive people than in recreational athletes.

The practical read: if you have to drop to the minimum, the engine is the half that punishes neglect fastest. Don't let the hard run be the session that goes. Detraining: strength versus endurance covers the timelines in more detail.

Still gaining on a small dose#

Maintenance is one thing. Getting stronger on very little is another, and it's been tested in trained lifters.

Androulakis-Korakakis and colleagues looked for the smallest dose that still raised 1RM in resistance-trained men, meaning at least a year of lifting.⁶ Six studies qualified. In all of them, one set per exercise done one to three times a week produced significant 1RM gains. Pooling five of them, the lowest-dose groups gained 12.09 kg on their 1RM overall (95% CI 8.16 to 16.03), 17.48 kg on the squat (8.51 to 26.46) and 8.25 kg on the bench (0.68 to 15.83).

The conditions matter more than the headline. The protocol was one set of 6 to 12 reps at roughly 70 to 85 percent of 1RM, two to three times a week, taken to failure, for 8 to 12 weeks. The authors call the gains suboptimal, meaning more volume gets more. They also say it's unclear whether the same holds for the deadlift, for trained women or for highly trained strength athletes.

Iversen's review gives a slightly fuller floor for anyone short on time: at least 4 hard sets per muscle group per week in the 6 to 15 rep range, 10 or more if you want more muscle, built on one squat or leg-press pattern, one pull and one push.⁷ Supersets, drop sets and rest-pause roughly halve session time for the same volume, though they're probably better for size than for strength.

Making short sessions shorter#

When time is the limit, the session around the sets is where it leaks. Iversen's review has three time savers with evidence behind them.⁷ Keep the warm-up specific to the lift: a few lighter sets of the exercise you're about to do, not twenty minutes of general prep. Only stretch if flexibility is actually a goal. And pair exercises that don't compete, like a press with a row, so you rest from one while doing the other.

None of those touch the load on the bar, which is the part maintenance depends on.

Matching the dose to the situation#

The numbers above translate into different weeks depending on why time is short. These are our applications of the doses, not tested protocols.

The pattern is the same in every row: frequency and volume shrink, intensity doesn't.

A 4-hour week#

Here's a week that fits those doses into four hours. It's our template, not a tested programme, built to keep both halves moving rather than just holding.

Where 4 hours go

	Lifting (min)	Hard run (min)	Easy and long runs (min)	Total (min)
Week	100	40	100	240

hybridAF's 4-hour template above, by session type. Our design, built from the doses in Spiering 2021, Androulakis-Korakakis 2020 and Iversen 2021.

That gives each major muscle group at least 4 hard sets a week across two sessions, one genuinely hard run, and three runs in total. The hard run sits three days after squats and the long run two days after deadlifts. If a week goes wrong, cut the Tuesday run first and Lift B second. Keep Monday's heavy lift and Thursday's hard run. They're the ones that carry the intensity.

Spreading this over more days is in how to split a hybrid training week, and sets per week in more depth are in how much lifting you need when you also run.

How to tell the dose is holding#

You don't need a lab. Pick one marker per half and recheck it every four to six weeks.

For strength, a top set you already do: the weight you can lift for 3 to 5 good reps on your main squat or deadlift. If that holds, the dose holds. If it slips more than a rep or two over a month, add a set before you add a day.

For the engine, a repeatable effort: the same route at the same effort, or a 5K time trial. Heart rate at a fixed easy pace works too if your conditions are steady. If the time drifts, protect the hard run first.

Change one thing at a time when you adjust. Otherwise you won't know which change did it.

What the research doesn't tell you#

Apart from the trained-men analysis, most of these studies are of untrained or recently trained people, over weeks to months. Spiering's review says plainly there's too little data on athletes. Nobody has tested the minimum dose for someone holding both halves at once over a year. Use the numbers as a floor to plan from, and watch your own numbers to see whether it's holding.

That last part is where a score helps, with one honest asymmetry. In the Hybrid Score, the engine half only counts recent efforts: runs and rides from the last 90 days, and a watch's VO2max reading from the last 120. Stop training it and the evidence ages out. The one exception is a logged HYROX race finish, a last-resort fallback that doesn't expire. The strength half grades your best logged lifts, so it holds until you lift something heavier. That matches the research above, roughly: the engine is the half that needs regular proof.