There are two main camps in the argument of exactly how we manage to move forward as we run. The traditional camp says that the body uses the muscles to “push against the ground.” The other—constituted almost solely by Dr. Nicholas Romanov’s Pose Method—proposes that we move forward thanks to the action of gravity on our bodies.
This second camp suggests that what the muscles do—their primary function—is to convert the downward force of gravity into net forward movement.
But how is it possible that the body can convert a downward force into horizontal movement?
Part of the answer lies in the fact that the running movement isn’t really horizontal. It consists of a wave-like movement of the hips and torso—an oscillation—that only seems to be a straight line if we’ve zoomed out far enough. If your model (incorrectly) assumes that the body is trying to convert a downward force into a force that travels on a horizontal linear vector, you’ll end up quite confused.
(But that’s a discussion for a different post.)
Let’s get to the issue I want to talk about: Proponents of the idea that runners “push off” often understand Dr. Romanov’s argument—that gravity is the “driving force”—as claiming that gravity provides “free” or “additional” energy (a.k.a. net energy) if we adopt a certain technique.
I believe that’s a rather shallow misrepresentation of what Dr. Romanov’s Pose Method has actually suggested. Pose’s main message regarding the action of gravity in running is quite a bit more profound. To explain why this is—and what I believe the main message of Pose is—let’s abstract away from mentions of “gravity” for a second and talk about a more general concept: downforce.
Instead of runners, let’s look at race cars. What are the necessary factors in making them go?
First and foremost, a race car needs a powerful engine. Without an engine, it’s going nowhere. But an engine is not enough. As any connoisseur of modern racing will tell you, there came a point in the evolution of car racing in which the engine’s ability to turn the wheels exceeded the ability of the best tires to grip the best track.
Why? Engine power eventually exceeded the car’s weight (defined as “how much force is generated as gravity accelerates its mass towards the ground”), and the capacity of the tires and the track to covert that weight into friction.
This reveals an important truth about the car: the engine actually isn’t for moving the car forward. The function of the engine is to spin the wheels. (While this results in driving the car forward, actual forward motion only occurs insofar as the power with which the engine spins the wheels coincides with the extent to which gravity keeps the car on the track.)
At this point, the only way to achieve greater speed was for engineers to somehow find a way to add to the downward force that gravity exerts on the car. How did they solve this dilemma? By adding the ugly inverted wings we now see on the back of every Formula 1 and drag racer: spoilers.
By redirecting the flow of air upwards at the tail end of the car, spoilers create another significant downforce. This reveals that strictly speaking, it isn’t gravity that allows race cars to move forward. It’s downforce. (Gravity just happens to be the quintessential downforce on Earth.) But the point is this: no downforce, no movement.
Let me spell out the implications in the strongest possible terms. Muscle power is NOT the driving force. It is the intermediary force. It converts a downforce into a quasi-horizontal oscillation. The driving force—the thing that ends up as movement—is gravity. Muscle power (a.k.a. metabolic energy expenditure through muscle use) is what lets gravity end up as movement. Gravity could provide zero net energy (zip, nada) and still it makes sense to call it the “driving force.”
The important question to ask about running isn’t really whether one running technique “uses” gravity to run—all running necessarily does so. Let me be even more specific: all overground movement is a result of expending energy in order to convert some downforce into a quasi-horizontal movement. The degree to which movement occurs is commensurate to the degree to which the organism/machine is harnessing downforce in real time.
Running according to the tenets of The Pose Method gets you “free energy” from gravity in the same sense that a car that never fishtails also gets “free energy.” In other words, Pose offers the cheapest way, all things considered—speed, agility, endurance, resilience, performance consistency, performance frequency, metabolic flexibility, recovery, longevity, etc.—to convert as much downforce as possible into overground movement. The critical observation offered by The Pose Method, then, is about how the body’s “engine”—its musculature and various systems—work best to harness the force of gravity to produce forward motion.
If the car weighs too much for the engine, it stays put. If engine power exceeds grip, it spins out. In other words, car’s absolute theoretical speed limit on Earth isn’t set by the power of the engine, the design and engineering of the transmission, or the materials it’s composed of. The maximum horizontal speed that any object can achieve is set by the theoretical limit to which it can harness the few downforces available to it on Earth. Once the car’s power and engineering causes it to reach speeds at which it is impossible to stop the air around it from supercavitating (creating a vacuum around the skin of the car), no aero kit will allow it to go faster, and no further improvements to the drivetrain will do it any good.
Of course, unlike race cars, the human body is not set up to use wind as a downforce—and we couldn’t run fast enough to make it matter anyway. Our running speed is a function of our ability to harness one downforce: gravity.
For a runner, improving efficiency by harnessing the force of gravity can mean 2 things:
- Removing power leaks and other muscle use that does not contribute to harnessing gravity. (The race car example would be to swap in better and better parts, and to make sure that you don’t throttle up enough to drift the car).
- Increasing top running speed: a runner with good form (a.k.a a runner whose movements and stances maximize the harnessing of downforce) can do so to a greater degree—in other words go faster—than an identical runner whose movements and postures do not effectively harness downforce.
Note that #2 is a hidden efficiency: it only reveals itself insofar as the runner goes faster. Both the inefficient runner and the efficient runner may be using a very similar amount of energy at lower speeds, but only the more efficient runner can get to a faster speed.
Pit my Toyota Tacoma against a Ferrari. Both would perform quite similarly at lower speeds and wide turning radii. If you ask both of us to make a wide sweeping turn at 60 miles an hour, we’d perform almost identically. You’d say “Whoa! Correcting for weight, they’re equally as efficient!”
But this observation only holds at lower speeds. If you increase the speed to 160 mph and tighten the curve, my Tacoma would start to spin out or come off the track, forcing me to reduce my speed. In other words, even if you doubled the horsepower on my Tacoma, I wouldn’t be able to match the Ferrari because of its stiffer suspension, better tires, lower profile, and aerodynamic design (in other words, it’s much better at harnessing downforce).
I believe that the discussion of “saving energy through the use of gravity” is meant to help us recognize—for starters—that we move forward only to the degree that friction and muscle power meet. It also has a few other implications (to put it mildly), but those are best left for another post.
UPDATE: Check out what I’ve written on The Pose Method:
About Pose theory of movement in running.
About Pose theory of movement in all sports.
6 thoughts on “The role of downforce in forward motion.”
Interesting take on this topic. You have a fascinating way of conceptualizing things.
I discussed this at the last Pose conference a few years ago. The way I summarized it was like this. When muscles are applying force, there is no forward movement, and when there is forward movement, the muscles are not applying force.
When the muscles are working, they are working against gravity to build a “reservoir” of potential energy coming into position (aka the running pose). When a runner moves forward, she or he is passively converting that potential energy into kinetic energy via gravitational torque while holding her or his body rigid enough to create a lever.
Gravitational torque is gravity acting over a lever. In this case, the runner’s body. As most people don’t seem to understand, levers change the direction of an applied force along an arc, and this allows for manipulating the force of gravity to have a horizontal component.
I’d like to think we are saying the same thing 🙂
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Glad you liked it!
Yes, I absolutely agree. I really like your point about creating a “reservoir of potential energy.” Your final point about the lever is also extremely important. Also, a lot of people don’t seem to get that the human lever (the leg) extends, which is why we don’t lose altitude with every step. I’m sure you’ve heard that argument before.
What I was trying to say here more than anything is that gravity is the driving force as much for race cars as it is for human runners (or for anything else).
HOW gravitational torque creates the running motion is the next discussion I’d like to have—essentially a longer version of what you just said—but here I wanted to get across the fact that gravity essentially HAS TO BE the driving force for any movement, race cars or otherwise.
I wanted to get the “what” out of the way first before moving on to the “how.”
Just to be clear about the discussion of linear vector vs. oscillation, I was answering people who think that humans “push forward.” While the action of gravity on a lever does create forward movement as you and I know, it isn’t a “forward linear vector” (meaning a “mathematically perfect straight line”) as a lot of these guys insist.
Essentially, the rotational component plus the (minimal) altitude changes of the GCM means that there’s always going to be a small oscillation. What these guys don’t understand is that a super tiny oscillation and zero oscillation (a forward linear vector) are two entirely different kinds of movements. Calculating according to the latter instead of the former is what makes them throw their hands up and say “That Romanov guy must be CRAY!”
“Essentially, the rotational component plus the (minimal) altitude changes of the GCM means that there’s always going to be a small oscillation. What these guys don’t understand is that a super tiny oscillation and zero oscillation (a forward linear vector) are two entirely different kinds of movements.”
Yes! Excellent description.
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Ivan, well done! I couldn’t have explained it better. Very succinct and clear. Thank you!
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Thank you! I’m very glad you liked it.