Science of Running blog recently put up a long, thorough post explaining his thoughts about "How to Run." One of the things I found interesting about his post was his discussion of the use of "cues" to help one improve running form. Often, as Magness admits, the cues are an exaggeration of what happens in reality, the purpose there being to get a runner to change form in the direction wanted by thinking in terms of a cue that overshoots the actual goal. As an example, here's what Magness has to say about cues used with the goal of getting a runner to shorten their stride (to avoid overstriding - more on this below) and adopt a more midfoot/forefoot footstrike:
"Sometimes when giving cues it helps to overemphasize the point, such as telling a runner to feel like they are putting their feet down behind them when correcting foot strike. Since “normal” is incorrect, such as reaching out and heel striking in this example, sometimes over-correcting is necessary initially."As indicated, the basic goal of the above cue is to help a runner to avoid overstriding (see Asics advertisement photo below for a demonstration of overstriding), which is when a runner reaches out ahead of the body with the lead foot and (typically) heel strikes with an extended leg (I should point out that overstriding and heel striking are not necessarily always linked). Overstriding can lead to the generation of braking forces and deceleration of the body upon footstrike, reducing efficiency and potentially increasing risk of injury due to impact shock transmitting up the leg. While there is debate about a lot of aspects of running form, avoidance of overstriding is one thing that most people seem to agree about (though some have questioned if we even have an accurate definition of overstriding). Returning to Steve's cue, the reality is that the runner will never "put the foot down behind them," but consciously thinking about this cue can help the runner to land closer to their center of gravity and avoid the dreaded overstride.
The reason I started this post by talking about cues and overstriding is because one of the pieces of advice I see most frequently in descriptions of "proper" or "optimal" running form is to land with the lead foot directly under the center of gravity of the body, thus avoiding an overstriding gait. If you're not familiar with the "center of gravity" (COG) concept, it simply refers to the average location of the mass or weight of an object. For example, if you were to try to balance a pencil perpendicularly across your extended finger, the location where you could balance it evenly without it falling off would be the center of gravity of the pencil. In a human standing vertically, the center of gravity is located somewhere along the midline of the body extending from the head through the hips (closer to the hips). If you were to lean forward, the center of gravity would move forward as well.
Advice to land directly under the center of gravity is all over the place, and it is one of the principles of popular running styles like Chi, Pose, and Newton's natural running. For an example, watch this video featuring Danny Dreyer, founder of Chi Running:
Let me start by saying that I agree with some of what Dreyer says in this video, and my goal here is not to criticize Chi Running – a lot of people swear by it, and if it works for you, by all means keep it up. My problems are more in the details and the fact that my observations don’t match up with some of what I am hearing. Dreyer's demonstration and description of the problems associated with overstriding and dorsiflexion of the foot make sense (I’m intrigued by the relation of foot dorsiflexion to shin splints). I’m a bit less convinced on the forward lean issue as Robert Cheruiyot won the 2010 Boston Marathon with what looks like a pretty upright posture to me (Meb looks pretty upright as well…).
Where Dreyer completely loses me is when he says to “Remember one thing…don’t ever step past your hip” and then goes on to explain that whenever he lands his foot is either “directly underneath” or “sometimes even behind” his center of mass. “I don’t want my foot to land in front of my hips, ever…” says Dreyer. What he seems to be saying is that any landing in front of the hips will introduce braking forces into the stride and reduce efficiency. If this is indeed the case, one would expect that runners who rely on having an efficient gait in order to make a living (i.e., elite racers) should never land in front of their hips as the “braking forces” generated would surely put them at a competitive disadvantage.
In my previous post on running form variability I used still images captured from high speed footage (300 fps) of the top runners in the 2010 Boston Marathon to address variability in running form (see below). Following the logic outlined above regarding landing under the center of gravity, a runner with a vertically oriented torso (like Robert Cheruiyot or Meb Keflezighi in the images below – we’ll ignore that they’re "not supposed" to do this), the goal would be to have the foot land directly under the hips. In a runner with a forward lean (like Tekeste Kebede or Ryan Hall below), the foot would land just a bit further forward, but still under the torso. (note - the apparent downward grade in the images is likely due to a tilt in the camera position given that the segment of the course where the video was taken was relatively flat - Washington St., just before turn onto Commonwealth Ave.)
In looking at the above pictures, it is quite obvious that none of the four runners are striking directly underneath the center of gravity at the moment of initial contact of the foot with the ground - all four of them are landing well in front of the hips. In an attempt to look at this further, I pulled four additional images synchronized to the moment where the entire sole of the foot comes into ground contact to support the weight of the body. On these images I drew a line from the center of the ankle joint through the knee joint, and then extended the line vertically through space to see where it fell relative to the center of gravity (see below). In all four runners, it is clear that full foot plant occurs in front of the torso and hips, and thus none of these elite runners are landing with the lead foot directly under the center of gravity. I’m well aware that some elites can use their superior physiological traits to overcome technique flaws and still perform well, but when all of the top 5 finishers (I’ve confirmed it in Deriba Merga – 3rd place - as well) at the Boston Marathon are all doing the same thing, I, for one, stop and pay attention.
So all of these elite runners from Boston seem to be breaking a seeming "cardinal rule" of proper running form - or are they? Perhaps the reality is that they are doing what we should all do, which is to land slightly in front of the center of gravity, with the lower leg (below the knee) oriented approximately vertically, and a slight bend at the knee (Kebede does appear to have a bit more of an extended knee compared to the others in the pictures above - he finished second in the 2010 Boston Marathon). Maybe the advice to land under the center of gravity has little basis in reality, and we should view it as more of a cue than a description of what we should actually be doing while running.
When it comes to this whole topic of landing under the COG, I'll add that I have long been doubtful that landing directly under or (even moreso) behind the center of gravity is even possible (unless perhaps you are a sprinter accelerating off the blocks). It seems to me that if you were to land directly under your hips (or, better yet, behind them) with a forward lean, all you would really accomplish would be to pitch yourself face-first into the ground. Indeed, exercise scientists Ross Tucker and Jonathan Dugas from the Science of Sport blog state the following in one of their posts on running form:
"It's probably impossible to run with a landing directly beneath your centre of mass. That would require you to be leaning so far forward, you'd probably be able to to touch the ground with your hand! So the limit to balance also limits the ability to get that landing directly underneath the hips (or wherever the centre of mass is). Also, if you chop your stride too much, then you start to compromise on the benefit of having longer legs - you effectively shorten your 'reach'."Maybe I'm splitting hairs here, but I'm a very visual person and I value precision and clarity when I try to envision biomechanical principles. The idea that distance runners can actually run with a foot landing directly under the center of gravity seems more myth than reality to me, and if this is the case, advice to do this can lead to confusion in runners who don't recognize it for what it is (i.e., a cue).
The problem here is that I have seen stick figure drawings depicting runners leaning way forward and landing with the foot under the COG (e.g., this one) - maybe I'm wrong, but this looks totally unnatural. I've also seen still photos purporting to show runners landing under the center of gravity that clearly seem to be captured well after the moment of foot contact with the ground. I've seen other stick figure diagrams and animations that purport to show runners landing directly under the COG when they are clearly not doing so (see below). If you know of a true slow motion video demonstrating someone actually landing directly under the COG, I'd love to see it.
After examining my slow-motion videos, I tend to agree with Tucker and Dugas that landing directly under the COG rarely if ever happens in practice and is in fact probably nearly impossible in a distance runner moving at a steady speed. Again, I'm not trying to criticize Chi Running, Pose, Newton or any particular coach or other advocate of a type of running form. I think that ultimately what they are all doing is trying to get people to avoid overstriding, which is a very good thing, and something I am constantly working on myself. I just think we need to be a bit clearer and more precise when describing running mechanics, because to not do so leads to confusion and a lack of clear understanding. The last thing I'd want to see is a runner go out and hurt themselves by doing something like actually trying to land behind their center of gravity.
In the end, what I take from this is that the advice to land "directly under" the center of gravity is better stated as "land slightly in front of the center of gravity," or "slightly in front of the torso/hips" In this sense, this rule of running form is better viewed as a cue as advocated by Steve Magness to help a runner to shorten stride and avoid overstriding than it is a description of what your body is actually doing. The reality seems to be that our footstrike should occur somewhere between where it would while overstriding with an extended leg and the vertical plane defined by the COG. There will likely be variation from person to person in where and how this exactly occurs, but try thinking about it and playing with it next time you go for a run.
If, after reading this post, you are still unconvinced that runner should not try to land directly under the COG, I'll leave you with a video and a few images for you to ponder.
First, below is a video from the work of Daniel Lieberman at Harvard University. It shows an adolescent Kenyan boy who has never worn shoes and who runs "a significant amount every day." You'll notice that he has a very upright torso, and lands with a forefoot strike well in front of his center of gravity (hips). Given his lack of experience with footwear, this adolescent might be a reasonable example of how the human body is meant to run in its default state.
Second, below are still images of Kenyan adolescents running in both unshod and shod conditions, again from Daniel Lieberman at Harvard University. Notice the position of the foot in front of the body just prior to landing in both cases. The unshod boy is demonstrating what appears will be a clear forefoot strike (photo appears to be just prior to the actual moment of contact).
Finally, below are two pictures showing my 6 year-old son running barefoot. He spends most of his time, by his own choice, running around and playing barefoot or in Crocs. It is virtually impossible to keep him in any form of regular shoe for any length of time. Notice his posture and foot position at landing in each of the images - relatively upright torso, foot slightly in front of the center of gravity and striking on the forefoot (at least in first picture, second is hard to tell), and lower leg perpendicular to the ground at contact. None of this was coached by me or anyone else - he's just doing what a little boy does when he runs. I'm not a full-time barefoot running advocate (I've only run barefoot a handful of times myself), but I do feel that these images are instructive. I'd love to hear what you think.
Update 8/19/2010: Steve Magness from the Science of Running blog sent me an image compilation - see below - taken from high speed video captures of himself (top two images) and some of his former runners, all of whom now run in college at the Division 1 level (bottom images). Note once again the location of foot contact.
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