Progressive Running

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What is the source of propulsion at running?

Welcome to another post here at Progressive Running, your trusted companion on the journey to better running.

As we individually lace up our shoes and hit the trails, it’s easy to overlook the complex interplay of forces at work with each stride. Many of us, myself included, have long believed that running is all about the powerful push-off from our legs, a testament to our muscular strength and endurance. But what if I told you that this widely accepted notion might not be entirely accurate? The true secret to efficient running might just lie in the art of falling forward. Yes, you read that right. Intrigued? Let’s dive deeper into this concept and unravel where many runners often go wrong about the source of propulsion in running.

Truth about source of propulsion at running

The true source of propulsion in running may be something we often overlook – the force of gravity, or more specifically, the gravitational torque. This concept, often referred to as “falling forward,” is a more efficient way to harness the natural forces at play during running. As we lean forward while running, our body’s center of mass moves ahead of our point of support, creating a torque due to gravity. This gravitational torque propels us forward, initiating the next step. Instead of wasting energy pushing off the ground or moving upwards, we’re essentially allowing gravity to do the work for us. This method of propulsion is not only more energy-efficient, but it also reduces the impact forces on our body, potentially leading to a lower risk of injury.

Building on this understanding of gravity as the primary source of propulsion, we can reframe our perspective on the role of our muscles in running. Rather than being the primary drivers of forward motion, our muscles, in fact, facilitate the use of gravity for propulsion. The key lies in coordinating our muscular actions to maintain balance and control as we allow gravity to pull us forward. For instance, our quadriceps control the descent of the body’s center of gravity after landing, while our hamstrings help to quickly lift the foot off the ground, preparing for the next stride. Our core muscles help maintain our body alignment, ensuring that we lean forward at the right angle to optimize the gravitational torque. In this way, our muscles work in harmony with gravity, not against it, to move us forward efficiently and sustainably.

Beating general public misperception of movement

Quads do not propel us

Becoming a bit scientific, in a fascinating study shared on the Pose Method website, titled “Theory & Practice: The Extensor Paradox in Running”, the conventional understanding of running propulsion is challenged. The research reveals that the quadriceps, muscles we often associate with the ‘push-off’ phase in running, actually cease their activity immediately after the mid-stance. This surprising finding contradicts the widely held belief that leg extension and muscular push-off are the primary sources of forward propulsion in running. Instead, it suggests a more nuanced understanding of running mechanics, where the role of the quadriceps is primarily to control the descent of the body’s centre of gravity after landing.

Calf muscles cause trouble

Another common misconception about running propulsion involves the use of the calf muscles in a technique often referred to as “pawback” or “toe push-off”. This method, while seemingly intuitive, may not be as efficient as one might think. The force generated during this action aligns with the extension of the standing leg on the ground, but it’s important to note that this force is not primarily horizontal. Instead, it has a significant vertical component that propels the runner upwards. This upward motion can be inefficient on two fronts. Firstly, the energy expended to move vertically is essentially wasted, as it does not contribute to forward momentum. Secondly, the subsequent descent from this heightened position increases the impact pressure upon landing, potentially leading to greater wear and tear on the body.

Top runners are not perfect

Even the world’s top runners are not immune to the challenges of achieving perfect running form. The ideal model of running, where every stride is a seamless interplay of gravity and muscular coordination, is a lofty goal that is difficult to attain. This is due to the complex nature of running, which involves not just physical prowess, but also intricate biomechanics, precise timing, and a deep understanding of one’s body. Even elite runners have their unique quirks and idiosyncrasies in their running styles, which may not align perfectly with the theoretical ideal. However, this doesn’t diminish their accomplishments or their mastery of the sport. Instead, it underscores the fact that running is a deeply personal endeavour, and perfection lies in continuously learning, adapting, and striving to improve, rather than achieving an elusive ideal.

Watch this video, form analysis of Usain Bolt by Pose Method. Amazing to see the room for improvement for a world champion! There is hope for those who want to beat him ;)

Vertical Oscillation Explained

What is vertical oscillation?

In running, vertical oscillation, or VO for short, is the distance the centre of body mass travels vertically (up and down) at each stride. The downwards VO is equal to and is a consequence of the upwards VO.

Is vertical oscillation good or bad?

Excessive VO is bad for sure however very low VO or zero VO (if possible, at all) are also signs of inefficient running technique. Excessive VO is a sign of pushing off the ground, and low VO is a sign of overstriding that usually comes with landing ahead of the body.

Essentially, VO is where the energy in our muscles convert into mechanical energy, and then released into forward movement. More details, if I can concise it into simple words as much as I can, it works as follows:

  • VO upwards: when we load our body with potential mechanical energy by adjusting our height (using muscles, tendons releasing elastic energy, all going against gravity)
  • VO downwards: when we rotate around the foot on the ground (source of propulsion), followed by landing (dipping down, tendons recoiling)

The bottom line is, to optimise vertical oscillation you must correct your running technique.

How bad is excessive vertical oscillation?

Over a long course of running, it is like climbing up a tall building in addition to running your running course.

For instance, if you run a [full] marathon (42.2km or 26 miles) in 4 hours at average cadence of 180 strides per minute, and you only have 1cm (0.393 inch) excessive VO, the total vertical distance you excessively climb up during the race is:

4 (hours) x 60 (minutes) * 180 (spm) * 0.01 (meter) = 432 meters or 1417.32 feet or 472.44 yards

It is pretty much like climbing up Steinway Tower in New York City as well as running your marathon race.

Which phase of VO is more expensive, upwards or downwards?

Upwards because going against the gravity is more costly; however, if you dip too low at every landing, you will have to go up a longer way to fall forward again :)

The [vertical] length of the downward phase is equal to and actually the consequence of the upwards one (and when I say upwards, I mainly mean going above your own height). When it is higher than what it should be, the runner has to deal with a greater force at landing due to falling from a higher height. It may not sound concerning at first, especially because the deviation from the optimum amount is about a centimetre or two, but the longer the running course the higher wasted energy and the higher chance of injury. That is why excessive VO is bad. It hurts both ways, up and down.

Does running cadence (strides per minute) affect vertical oscillation?

It does but it is a crucial point to understand that cadence is a by-product of running, not something to be actively involved with. For instance, the golden 180 spm might be achieved while there is still an excessive vertical oscillation.

When falling forward is the only source of propulsion at running, and there is no overstriding, the cadence automatically falls around 180 spm (proven by studies, because it highly depends on the natural frequency of tendons).

How to optimise vertical oscillation in running?

Correct running technique is the solution for optimising vertical oscillation. Excessive vertical oscillation is caused by excessive movements during each running stride, mainly by pushing off the ground which is very common amongst runners. Apart from recreational runners, there are even some elite runners who push off the ground without knowing about the inefficiency of doing so.

There are inefficient running techniques in which VO is minimised. For instance, reaching ahead of the body minimises vertical oscillation. This minimisation is not in your favour because it causes more issues like:

  • Not using tendon elasticity: By not landing under the body (or close to the vertical line passing the centre of body mass), the runner does not benefit from elasticity of tendons by preserving the energy in them during landing. This energy is released in the next stride when we need to adjust our height to fall again, simply meaning saving energy or the so called efficiency.
  • Chance of injury: Reaching ahead (over-striding + landing ahead of the body) exerts excessive pressure on knees and other body parts (some physiotherapists relate ITBS to over-striding).

How is vertical oscillation handled in Pose running?

As far as pushing off the ground, active landing, and over-striding are eliminated in Pose Method of Running, vertical oscillation is down to its minimal possible range, which is mostly based on the range of stretch of some tendons in our legs.

In Pose method, falling forward is the only source of propulsion. To be able to fall again after landing, we have to go back to the same height. Adjusting height is done unconsciously. A portion of this height adjustment is done by the release of energy preserved in our leg tendons. This simply means efficiency.

Culture of running form

I am going through the online course by Pose Method to become a certified running coach. It is an interesting course that covers a lot of theories including Newtonian physics (glad I did physics well back at high school!), as well as videos of practical sessions. At one of the videos, Dr Nicholas Romanov talks about running culture which I found really interesting and I am going to talk about it from my own perspective.

Imagine you are invited somewhere for lunch but at lunch time everyone grabs a pot full of food and sits at a corner to gobble the food up. Do you see anything wrong at this scene? Let me ask you some questions before you answer:

  • Do not they get enough nutrients into their body?
  • Do not they save time by avoiding the chit chat at the table?!
  • Do not they have the freedom of eating it the way they want?!

It is obvious why this scene looks odd and out of norm because we all follow similar “dining culture“.

Source: www.babycentre.co.uk

Now another scenario, you are going to play soccer with some new friends that you have not played before. You are about to choose your team members and you see this guy at the following scene, would you want him in your team? no? why?

Source: www.letsbet.ie

The reason is, we have some images of good soccer players in our head and this guy does not fall near any of them. That means you are into the culture of right soccer moves and this one is out of the norm.

Now, look at this one taken from B-Line busses that go from Northern Beaches to the city and back. Is there something wrong with the drawings in blue?

Do you see it? let’s take a closer look:

See how the running girl is over-striding? do you see her back leg is trailing behind? see her foot is not moving towards her hips? or the toes pointing downwards right after leaving the ground indicating push-off?

If you do not see any of these, that means you have not honed your eyes to spot these running deviations. The other interpretation of it is:

We do not have a running form culture in our society yet

We do not pick such issues when we see these images. They are ubiquitous but we do not catch them. We are like the members of that family who eat their lunch in a pot at an isolated corner, so we do not see any problem with the way we eat.

Just go to any image stock site and search for running. On the bright side, such images help me hone my eyes better for spotting running issues ;) take a look of some samples here.

Leg trailing behind
Woman: pushing off the ground
Man: knee drive, likely to have late pull

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