Have I beaten newsbot to this?
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http://www.nytimes.com/2011/07/19/health/nutrition/19best.html?_r=2&ref=ginakolata
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Benefits of more complaint surfaces here:
http://biomech.media.mit.edu/publications/Ground_Stiffness_Metabolism.pdf -
Agreed- bit of a simple article...
I personally think that variety in terrain is one of the keys to injury prevention- much more important than how hard or soft the surface is. The obvious downside is that you my be more likely to have an ankle sprain due to the surface geometry. Hence why we have flat and even footpaths/sidewalks etc... -
P.S Also thought the article was poor -
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I'm not sure how it ties in with this but I am often surprised by long distance runners who train on the roads. They usually run into the traffic (on a left foot above the right camber) yet seem to have few problems with the greater supination moments at the right foot/ankle and the greater pronation moments at the left foot/ankle.
I suppose it suggests to me that the surface geometry might be less important. Or are you saying that the inconsistency of surface will be more likely to cause injury? -
Can't speak for CraigT, but personally I was referring to the step by step variation in surface terrain/geometry. (Although I don't believe it is a separate issue to the 'stiffness' discussion - rather that they are intrinsically linked).
Other things the research currently suggests:
- Running on a camber may increase injury risk
- Running down steep hills increases injury risk -
Last edited: Jul 19, 2011 -
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Are there any papers you don't have?
Cheers dude -
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I have often wondered if it is the horizontal "give" that you get when running on dirt and gravel is more important than the hardness of the ground with respect to injury. When running on concrete or pavement, there is a lot of traction but little or no horizontal give when landing. How much stress does that add to the body?
While there is less traction running on loose sand, dirt or gravel, that slight slide forward that occurs on impact and diffusion of stress before it is absorbed by the body might be just as important if not more than the vertical impact stress that is often the focus when it comes to injury.
Not a lot written about the relationship between shear stress and injury.
Dana -
Adidas played with the concept of allowing forward translation during initial contact by "decoupling" the strike plate of their formotion shoes. I guess Benno was probably involved in this. Most manufacturers have at some stage produced shoes with decoupled heel pods.
Shear stress where and injury? -
I'm not sure I understand your question. "Shear stress where and injury? Since I initially asked the question, "How much stress does that add to the body?" I certainly don't have the answer, not sure any one does given how little has been written about it.
One obvious injury I can think of from shear stress is blisters. I'm more curious if there is a relationship between shear stress and knee injury.
Dana -
I don't think that's what you meant, I think you mean shear force at the shoe-ground interface, in which case you need to understand how varying relative magnitudes of the shear and normal components influences the direction of the net GRF vector. If you understand this relationship and between the position of the GRF vector relative to the knee joint axis you can work out how increasing / decreasing shear component will influence the vector position, you'll then much better understand how increasing / decreasing shear at the shoe-ground interface might create an increased demand on certain tissues to provide internal counter-moment. Your understanding of functional anatomy will then provide you with the answer as to which tissues can provide such moment and as such are potentially at increased risk of exceeding their zones of optimal stress. -
So when comparing surface geometry to surface stiffness, it would make sense to also include shear force as a variable that might influence the outcome. -
If gravel etc means that the body is working harder to deccelerate and then accelerate -
Does any one know the answer? Can anyone point to a study that demonstrates if a relationship exists between the level of shear force at the shoe-ground interface and the frequency of injury.
I'm not trying to argue one way or the other, I'm just asking a question. -
Of course it makes sense to include friction, hence in my description of how foot orthoses work I use these three basic characteristics:
Load-deformation
Topography
Friction
They are as applicable to the shoe (foot)- ground interface as they are to the foot-orthosis interface. And it is a combination of these which will help to determine the net GRF vector and ultimately the external moment acting about the joints.
Also, you have to consider both halves of the contact period of running. Low co-efficient of friction is pretty rubbish when you are trying to accelerate. -
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We are again not communicating so forget it. -
lower friction the opposite.
As you know running is multiple decelerations and accelerations so having a lower friction may not be positive
as for studies no idea report back if you find any -
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Zones Of Optimal Surface Friction - ZOOSF :wacko:
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Running injuries due to road camber do commonly occur just as injuries may occur asymmetrically on the feet in track athletes who always run counter-clockwise on the track. The 3D surface geometry and the load-deformation characteristics (i.e. stiffness) of the running surface are very important when considering the mechanical cause of running injuries in patients. -
I was also making the point that race walkers seem to suffer with these types of camber related pathologies more which struck me as odd as they are both using the same cambered surfaces. It made me wonder about the mechanism of injury in a walker versus a runner. Then I realised that I see far more walkers than runners so my population is inherantly biased and therefore largely invalid for comparison
Regards,
Robin -
One of the problems with running on a surface such as sand or gravel is that the pushing force from the foot is not resisted sufficiently by the running surface so that the sand or gravel deforms under the loading force from the foot during the late support phase of running gait, when, ideally, the surface should be pushing back on the foot to propel the body forward.
The ideal surface for running is likely one that 1) deforms during the first half of support phase when the body is trying to absorb the impact forces of foot strike while the center of mass descends, and 2) then rebounds during the latter half of support phase when the center of mass is rising upward. Such a running surface was designed by Tom McMahon, PhD in the Harvard indoor track in 1977 resulting in what many call simply the "Harvard Tuned Track".
Here is a nice article that summarizes the concept of running biomechanics and surface stiffness as it applies to "Tuned Tracks".:drinks
http://www.pponline.co.uk/encyc/the...l-effect-the-quality-of-their-performance-312 -
Here's a nice article on energetics of running surfaces.
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My point or question really wasn't about the relationship between running surface and efficiency, I'm sorry for not being clear enough. CraigT referenced an article about running on soft ground and injuries which was the subject of this thread. The point I have been trying to make is that while there is a lot of discussion about the relationship between ground compliance and injury, I wanted to bring up that compliance is one variable but what about shear stress?
I have been running on dirt trails almost exclusively for the past over 20 yrs. I don't find the trails all that compliant. The dirt is packed as hard as concrete, there are sections of solid rock and so on. What really makes it different from running on pavement or concrete is that the surface geometry is quite variable and there tends to be a thin layer of sand and/or gravel over quite a bit of it.
The sand/gravel doesn't change the compliance to any significant degree but it does absorb some of the shear force energy upon impact and push off. I can absolutely feel my feet slide a small amount on impact and have a reduction in traction on push off. This is not an assumption, I can feel it. It is this very phenomenon that I believe is responsible for the dramatic reduction in speed that I experience when running on these dirt/rock trails vs pavement.
When I lace up my shoes, at this point in my life, I am not as concerned with my speed on a given daily run. Rather, I am more concerned with my level of aches and pains when I'm unlacing my shoes after I'm done with my run.
On a given day, I am OK with losing running speed/efficiency as a result of a loss of friction. I'm not OK with giving myself a daily pounding that pavement provides. What I am trying to point out is whether by loosing energy to a reduction in shear force, will that result in a reduction of stress on the body. Will that reduction of stress on the body manifest itself in fewer incidences of injury.
A common claim, right or wrong is that trail running is softer, easier on the body which results in less injury. My response, I'm not so sure, is it the softer, more compliant surface or does it have to do with the reduction of shear force? What is interesting is how often you will see soft surfaces and trails linked together but not a lot said about shear force. For that matter, look at how hard of a time I'm having trying to get my point across even here.
I am convinced, especially when running downhill that the little bit of give and reduction in shear force that you get when your foot hits the ground on a trail saves your body from taking the pounding that it would take when running down a similar decline on pavement.
As an example, look at an Olympic ski jumper, If it wasn't for the great reduction of shear force on landing, I bet their career would be very short.
Thoughts?
Dana -
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