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Running surface article

Discussion in 'Biomechanics, Sports and Foot orthoses' started by CraigT, Jul 19, 2011.

  1. CraigT

    CraigT Well-Known Member

  2. CraigT

    CraigT Well-Known Member

    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...
  3. Griff

    Griff Moderator

    My thoughts are aligned with this to a degree. You can't get repetitive strain injuries without the repetition.

    P.S Also thought the article was poor
  4. Ok, lets take injuries due to single traumatic events, such as inversion sprains, out of equation for a moment. What data do we have to suggest that variation in surface geometry is "much more important" than surface stiffness in injury prevention? I'm not saying I don't agree with you, I'm just saying it's worthy of exploration.
  5. RobinP

    RobinP Well-Known Member

    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?
  6. Griff

    Griff Moderator

    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
  7. RobinP

    RobinP Well-Known Member

    I thought that was what you were referring to but because you had mentioned about repetitive strain and removing that, I thought you were saying that step to step variations in the surface were less likely to cause injury. Otherwise known as jumping to conclusions
    I hadn't looked into the research, in the main because I have seen very few patients where this has been the case. Tends to be more a problem with race walkers in my experience. Reduced, if not negative base of gait, marked adduction of the whole leg and tibialis anterior firing like stink all makes for quite a supination moment to be resisted by the peroneals
    Last edited: Jul 19, 2011
  8. Griff

    Griff Moderator

    'may' is the key word there...

    Attached Files:

  9. RobinP

    RobinP Well-Known Member

    Are there any papers you don't have?

    Cheers dude
  10. Griff

    Griff Moderator

    Only just re-read this, and I don't think I made myself clear - your conclusions were right squire. It is my belief that step to step variations in surface terrain/geometry will result in repetitive strain injuries to be less likely. Not sure if the research backs this anecdotal finding up - will delve into it at some point tomorrow.

    See above :rolleyes:
  11. Dana Roueche

    Dana Roueche Well-Known Member

    In addition to comparing variation in surface geometry to surface stiffness, it would be helpful to consider shear stress as well.

    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.

  12. The magnitude of the shear component influences the angle of the net grf vector and as such influences the external moments acting about the joint axes.

    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?
  13. Dana Roueche

    Dana Roueche Well-Known Member

    Not sure how effective the shoes have been. Reebok currently pushes the notion of shear reduction with DMX Shear reduction technology as part of their Zig shoes.

    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.

  14. Hence my question, shear stress where? Shear force at the knee? Which tissues are likely to be important in resisting shear forces at the knee? Answering this will guide your google.

    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.
  15. Dana Roueche

    Dana Roueche Well-Known Member

    Right, so to net it out, a runner is better off running on natural surfaces such as sand, dirt, gravel where shear force is reduced at the shoe-ground interface rather than on pavement or concrete that will have higher shear-force at the shoe-ground interface.

    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.
  16. Why ?

    If gravel etc means that the body is working harder to deccelerate and then accelerate
  17. Dana Roueche

    Dana Roueche Well-Known Member

    Mike, huh? The body does work harder to maintain on gravel, sand, etc. The question has to do with whether there is a relationship between shear force levels and injury.

    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.
  18. It's not as simple as that. It depends on so many other variables which will also influence the position and magnitude of the GRF vector relative to the joint axes, for example angle of attack, position of limbs etc.

    Of course it makes sense to include friction, hence in my description of how foot orthoses work I use these three basic characteristics:


    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.
  19. You are asking the wrong question. What you should be asking is if there is a relationship between joint moments and injury. I've been patiently trying to explain to you that you should not view shear force in isolation, rather you need to consider its influence on the external moments acting about the joints. Take a google and see if you can find any literature which supports a relationship between moments and injury.
  20. Dana Roueche

    Dana Roueche Well-Known Member

    Actually, I was just trying to ask if a reduction in shear force by running on sand and gravel had any relationship to injury rate. This was also in consideration with surface geometry and surface compliance. Googling on that will not produce anything.

    We are again not communicating so forget it.
  21. Exactly in a high shear/friction surface the body will work less to decelerate the foot before accelerating again which may or may not mean less muscle strain

    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
  22. First, you need to show that there is a reduction in shear force when running on sand and gravel, I'm not saying there isn't, but you make that assumption. I've explained to you that you need to look at the influence that shear component has on the net reaction force vector and how this might influence joint moments. I've stated that you cannot simplify it to make the kind of statement you made, nor to answer the question you ask above. I agree, Googling it won't produce anything if you do not have the requisite knowledge and understanding to put the pieces of the puzzle together and use deductive reasoning.
  23. Dana Roueche

    Dana Roueche Well-Known Member

    Sure, thanks for your help.
  24. Dana Roueche

    Dana Roueche Well-Known Member

    Simon, thanks for being helpful, I bet you are feeling good about it.
  25. Zones Of Optimal Surface Friction - ZOOSF :wacko:
  26. Robin:

    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.
  27. RobinP

    RobinP Well-Known Member

    I'm sure the surface geometry is important. One thing that I have learned from following many of your discussions with Simon is that everything plays a part and that our conventional, common sense thinking should be questioned for mechanical/biomechanical validity. I made the statement with reference to the discussion with Ian about repetition and overuse. It prompted me to think about the runners that I have seen and how few, considering the amount of injuries, that are linked to the cambered running surface. I obviously don't see enough for it to be a representative sample.

    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


  28. Dana:

    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

  29. Here's a nice article on energetics of running surfaces.

    Attached Files:

  30. Dana Roueche

    Dana Roueche Well-Known Member

    Kevin, thanks. I agree completely regarding loss on a sand or gravel surface. I have found that my time running 20 miles for example is 10% faster on pavement than it is on the dirt trails I run on that has the equivalent elevation change. This loss in speed is really dramatic considering that Tom McMahon's track produced an increase in speed of approximately 2% which was considered quite significant.

    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.


  31. Perthpod

    Perthpod Active Member


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