Protein for runners and endurance training

Protein is discussed as a muscle-building nutrient, so endurance athletes often assume it is somebody else's problem. The requirement goes up with endurance training, for a different reason than it does with lifting.

Repair, not growth

A lifter eats protein to build tissue that was not there. A runner eats protein to rebuild tissue that was damaged.

Repeated loading over a long session causes muscle damage that has to be repaired, and the volume of that repair scales with how much training you do. At high volumes there is a second draw: some protein is used for energy when carbohydrate availability runs low, which is protein leaving the building rather than arriving.

Both of those raise the requirement above the general adult figure, and neither of them looks like muscle growth, which is why the need gets overlooked. In short:

• Repair scales with volume. More miles means more tissue to rebuild, and the rebuilding is made of amino acids.
• Some protein leaves as fuel. When carbohydrate availability runs low over a long session, protein is used for energy rather than for repair.
• Neither shows up as looking more muscular, which is why runners assume this is somebody else's nutrient.

Where the range sits

The position stand recommends 1.4 to 2.0 g per kilogram a day for people training to build or keep muscle, and describes intakes above that range as safe rather than better.¹ Endurance training sits in the lower part of that, and the number climbs with volume rather than with the sport.

For a 70 kg runner, 1.4 g/kg is 98 g a day. Most people training seriously and eating normally are closer to that than they expect, and the ones who are not are usually short at breakfast.

The bigger problem in this group

Underfuelling, and it makes the protein question secondary.

Endurance athletes are the population most likely to be eating meaningfully less energy than they expend, sometimes deliberately and often not. When total intake is low, protein gets diverted to fuel and the muscle repair it was meant for does not happen, whatever the number on the log says.

If your training volume has gone up and your weight is drifting down without you intending it, that is a fuelling conversation and worth having with a sports dietitian or your doctor rather than solving by adding a shake.

Lifting is not a distraction

Resistance training earns its place in an endurance programme, and it does more than one job here.

It supports running economy and injury resistance, which is why it appears in most modern coaching. And it gives muscle a reason to be maintained through heavy training blocks, which matters because the protein supplementation research found the effect on fat-free mass was larger in people already resistance-trained.³

Two short sessions a week is the usual recommendation. It does not need to interfere with the running.

Timing, briefly

The nutrient timing position stand is measured about all of this: total daily intake dominates, the post-exercise window is wide, and pre-exercise and post-exercise feeding overlap.²

For endurance specifically, the one timing consideration with a practical case is on days with two sessions or a long session, where getting protein and carbohydrate in reasonably soon afterwards makes the next session go better. That is a recovery argument rather than a muscle one. How much of the timing story holds up covers the rest.

Where this stops being general advice

These ranges are for healthy adults training normally. If protein intake is already managed as part of your medical care, that plan takes precedence, and any unintended weight loss during a training block is worth raising with a doctor rather than adjusting a macro target over.