Can you lift weights while marathon training?

Yes, and you should — strength work reduces injury risk and improves running economy. What changes is the goal: two full-body sessions a week at moderate load maintains muscle very well, and expecting to build during a marathon block is what turns a reasonable plan into a disappointing one.

How many days a week should I lift during marathon training?

Two, occasionally three in the early base phase. Ten to twelve fractional sets per muscle per week is enough to maintain, and running volume in a marathon block leaves little recovery capacity above that. Frequency matters less than whether the sessions are recoverable alongside your long run.

Will I lose muscle training for a marathon?

Not from the running itself at reasonable volume with adequate protein. Muscle loss during marathon blocks is almost always an energy problem — chronic under-eating relative to a training load that rose while intake did not. Protein at 1 gram per pound and a maintenance figure that actually includes the mileage solves most of it.

Should I lift before or after running?

Separate them by six or more hours where possible; the measured interference falls from about -0.66 to about -0.10 at that separation. If they must share a session, run first during a marathon block — the running is the priority and the lift is maintenance work.

Lifting While Marathon Training

Q: When should I stop lifting before a marathon?

Keep lifting through the taper at reduced volume rather than stopping entirely. Stopping removes a stimulus your body is adapted to at exactly the moment you want nothing to change, and the last heavy lower-body session should be about ten days out.

The block plan

Phase	Weeks out	Lifting	Why
Base	18–12	3 sessions, 12–14 fractional sets/muscle	Mileage is lowest here. This is the only window where building is realistic
Build	12–4	2 full-body sessions, 10–12 sets	Mileage peaks. Hold, do not chase
Taper	4–0	2 sessions, reduced volume, load maintained	Keep the stimulus, drop the fatigue
Race week	—	One light session early in the week	Movement, not training

The single most useful decision is made at week eighteen: name which goal is primary. It is the marathon. Everything else follows, and a lot of frustration disappears when it is said out loud.

What to cut, in order

Accessory volume. Lateral raises are not why you are tired.
Lifting frequency, consolidating to full-body sessions rather than dropping total volume proportionally.
Intensity on lower-body work in the peak weeks — moderate loads, not maximal.
Never the running. It is the goal.

What not to cut: protein, sleep, or the lifting entirely. Dropping lifting to zero during a block is how people arrive at the start line strong aerobically and with a body that has lost the tissue that took two years to build.

Scheduling around the long run

The long run is the session with the largest recovery cost and the largest fuel cost. It should not be adjacent to your heaviest lower-body work on either side.

A workable shape with a Saturday long run:

Day	Session
Mon	Easy run + full-body lift, 6 h apart
Tue	Quality run — threshold or intervals
Wed	Easy run
Thu	Easy run + full-body lift, 6 h apart
Fri	Rest or very easy
Sat	Long run
Sun	Rest or recovery run

Lifts land Monday and Thursday, both at least two days from Saturday. The quality run is Tuesday, so it follows the Monday lift by a full day rather than sharing legs with it.

Six-hour separation matters: same-session concurrent training carries an effect size around −0.66, and six hours or more drops it to about −0.10. The detail.

The energy failure, which is the real one

Marathon training is expensive in a way people consistently underestimate.

Running costs roughly 1 kcal per kilogram of bodyweight per kilometre, net of resting. For a 165 lb (75 kg) runner:

Weekly mileage	Extra daily cost
20 miles	~345 kcal/day
35 miles	~600 kcal/day
50 miles	~860 kcal/day
65 miles	~1,120 kcal/day

Peak marathon weeks add over a thousand calories a day for many runners. If intake does not move with it, you are in a large sustained deficit — and a large sustained deficit while training hard is exactly how muscle is lost, how bone density falls, and how the endocrine consequences of low energy availability begin.

This is not solved by eating more on faith. It is solved by measuring maintenance from what your weight actually did against what you actually ate, so the mileage is counted whether or not you tracked it. The method.

Protein through a block

1.0 g per pound of bodyweight, and do not let it fall when calories are hard to hit. If protein is being squeezed to make the calories work on a peak week, the calorie target is wrong, not the protein.

Distribution matters as much as the total: roughly 25 to 35 g of quality protein clears the leucine threshold and the response lasts two to two and a half hours, so four feeds of about 40 g beats one large dinner. On a day with a long run and a lift, that is not optional.

Iron, specifically

Endurance training depresses iron status, and running does so through a mechanism cycling does not have — foot-strike haemolysis, the mechanical destruction of red cells in the feet with every stride. Add sweat and gastrointestinal losses and a marathoner's iron requirement is meaningfully elevated.

Low iron is one of the most common correctable causes of unexplained fatigue, declining performance and poor recovery in runners. Its symptoms are indistinguishable from overtraining and under-eating, which is exactly the differential you are already trying to sort out at week fourteen.

Get ferritin measured rather than supplementing blindly — excess iron is harmful. What to track and what it cannot tell you.

The taper, and lifting through it

Keep lifting through the taper at reduced volume with load maintained. Stopping entirely removes a stimulus your body is adapted to at exactly the moment you want nothing to change.

The last heavy lower-body session goes about ten days out. After that, movement — two light full-body sessions in the final fortnight, nothing that produces soreness.

After the race

The window immediately after a marathon is the best building opportunity of your year, and most people waste it by either doing nothing for a month or jumping straight into the next block.

Two to three weeks of genuinely reduced running, then a strength-primary block: three or four lifting sessions, 14 to 18 fractional sets per muscle, endurance held at easy volume only. Your aerobic base decays slowly and your capacity to build muscle is at its highest when running volume is lowest.

That is where the muscle you did not build during the block actually gets built.

What to do next

Before week one, measure your maintenance at your current mileage, then re-measure at week eight when volume has risen. The gap between those two numbers is what your intake needs to move by, and almost nobody does this — which is why "I lost muscle marathon training" is so common.