Does cardio build muscle?

Question

One of the factors of muscle growth is mechanical tension which can be achieved throughout various methods. One of them is moving weights around, the other is pushing maximally against an immovable object.

Does pushing a wall build muscle? Because if it does, so does running, when running one outputs maxim force onto the ground to gain as much forward thrust as possible to break the air barrier in the smallest amount of time.

After the trainee gets tired, force decreases but effort remains unchanged, speed might have decreased by 50% after 15 seconds but effort is maintained at 100% because they are not trying to go slower, they are fighting the sense of musclular pain to keep going the fastest they can in each second passing.

Another factor of muscle growth is metabolic stress, and anyone who has ever ran knows that a 1 kilometer sprint is tremendous, truly comparable to a set of deadlifts to failure in therms of metabolic stress build up.

The one missing factor is muscle damage, when running or biking, rowing or doing pretty much any cardio the muscles are only going through a concentric contraction and never an eccentric which seems to be the one causing the most muscular damage.

So assuming one is always in a caloric surplus to aid muscular growth, as seen in scientific studies that muscle gain with caloric deficit is so small it is regarded insignificant - Antonio Paoli, Keith Grimaldi, [...], and Antonio Palma .

And one is always running at 100% effort

Can they build muscle at the same pace of weight training?

Answer 1

This is going to be a yes and no answer, and here is why.

If you start from nothing, you will have not have a lot of muscle mass in your legs. Cardio activities such as running, sprinting and cycling will indeed increase muscle mass at this point. It wont grow at the same rate as if you were doing strength exercises though.

The reason for this is because the body is very good at adapting repeated action. If you demand you body to maintain a 30min run for 5 days a week, it will become better at running for 30min. You're training the body to be able to last that long on a high pase. At some point this won't necessarily require more muscle mass but rather require things like more lung capacity and a stronger heart.

The second thing you already mentioned yourself, muscle damage. This will get quite limited at a certain point, which prevents you from making any real gains just from running alone.

Another thing that you miss is range of motion. In order to stimulate muscle growth you want both a stretch and a full contraction during a movement, you don't achieve this during a run.