Is Running Enough for Leg Strength?

by Karl Schudt | February 11, 2016

“I don’t need to do squats. I run!” Have you ever heard this? I have. The question: does running give you adequate leg development, so that you can concentrate on your biceps?

No, it doesn’t. In my experience and that of coaches I’ve spoken to, runners are among the weakest trainees we see. I’ve had healthy marathoners who couldn’t squat 45lbs.

Why is this? After all, they are getting lots of leg work, right?

They are getting lots of leg exercise but almost no leg training. They are doing things with their legs that make them tired (and perhaps gives them a runner’s high), but don’t make their legs stronger. Why not?

It’s not hard enough.

Runners running long distances are not stressing their body very much on any individual stride. The proof is that you can run for a long time. If it were hard, you’d have to stop. Running may be uncomfortable, and there may be pain involved, but it’s just not that hard. A marathon is not a muscular stress, it’s a cardiovascular stress. You are getting better at extracting energy for the demands of long bouts of running, perhaps by increasing the number of mitochondria, but you aren’t getting stronger.

There’s no progressive overload.

When you first start running, it will be hard on your legs, especially if you are untrained. This rapidly changes as you adapt to the mild muscular demands of the activity. An untrained person will get a little stronger at the beginning, but just getting off the couch will have a training effect for the severely untrained. But you adapt to the strength demands very quickly (1).

Selye’s General Adaptation Syndrome explains this: When an organism experiences a stress, it will adapt to that stress through some sort of change of the organism. It will only adapt to that stress, and repeated bouts of the same stress won’t cause any more adaptation. Ten minutes of sun every day won’t give you a dark tan, because you’ve adapted to the ten minutes, you don’t have to get very dark to adapt to ten minutes in the sun, and then it’s not a stress anymore. Playing the guitar will put calluses on the tips of your fingers, but not on the rest of your hand. Running will cause you to adapt the small amount you need to in order to support the strength demands of running, but no more. You need to increase the stress. You need to train.

You could run with rocks in your pockets, but it would be far more efficient and easier on your joints to get yourself to the squat rack.

Running relies on elastic rebound.

It’s true that while running, your legs are impacting the ground with a force of about 2000 Newtons (about 450 lbs of force) (2). Up to 60% of this comes from stored elastic energy (3), so it’s more like 180lbs of force from each leg’s contractile tissues. This is still considerable, right? Why isn’t that enough to make me strong? After all, that would be a 340lb squat. Actually, it would be 340 pounds minus your bodyweight, so perhaps a 160lb squat, if you weigh 180 lbs.

But this is still through a very small range of motion. In order to cause a strength adaptation, we want to use the most muscle mass over the longest range of motion with the most weight. In running, there is a light weight moved through a very small range of motion.

Look at the left leg of the runner in the picture: The angle of the knee at the point of impact is only slightly greater than the angle at the push. To put it in barbell terms, it’s like a quarter squat, or more like an eighth squat. A 1/8 squat would not cause much strength gain even if the load were increased. Quarter-squats don’t produce strength gains in anything but quarter-squats and neither would 1/8 squats (4).

Furthermore, there’s very little involvement of the posterior chain. The hip angle may change 30 degrees from impact of the foot to lift-off, and much of the hip extension occurs because of the momentum of the runner. The hip extensors are left largely unstressed, so much so that long-distance runners sometimes can’t even squat successfully with the 45lb bar.

What you need to know:

If you insist on running long distances, that’s your business, but you should know that your legs aren’t strong because of the running. Do your squats and deadlifts, get stronger, and you’ll be a better runner.

References

1. The Novice Effect
2. Cross, Rod. “Standing, walking, running, and jumping on a force plate.” American Journal of Physics. April 1999, 304-309.
3. Thys H, Cavagna GA, Margaria R. “The role played by elasticity in an exercise involving movements of small amplitude.” Pflugers Arch. 1975;354(3):281-6.
4. Hartmann et al. “Influence of squatting depth on jumping performance.” Journal of Strength and Conditioning Research 2012 Dec., 3243-3261.