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Blisters and taping

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Asher, Jan 20, 2013.

  1. Asher

    Asher Well-Known Member

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    Hi all,

    I've been involved in the topic of blister prevention lately and I have my doubts about taping as a blister prevention strategy. Myself, I've used tape in the past for heel blisters and it helped a lot. But I have some thoughts about how it helped.

    I noticed I'd still get a blister. But the helpful bit was it didn't de-roof.

    I think that shear (which is what causes blisters) still occurred. Shear is soft tissue distortion. Shear occurs even if nothing rubs against the skin. The skin remains in stationary contact with the sock but the bone moves relative to the stationary skin. So everything in between the skin and the bone stretches and distorts. The zone of least resistance to this stretching is the stratum spinosum of the epidermis - where blisters occur.

    Different to that, an abrasion occurs when something moves or 'rubs' over the skin. In the case of foot blisters, the skin moves relative to the sock and this abrades or rubs off the outermost layers of the epidermis. Of course if there is a blister, this 'rubbing' will take the roof of the blister off.

    So does tape negate shear and therefore blisters? I don't think so.

    But is tape a waste of time? No. Anyone would rather have a blister than a red raw sore. But is it an effective blister prevention method? I don't think it is.

    Does tape reduce blister formation even a little bit - I can't figure out how but maybe it does. If so, by what mechanism?

    I'd appreciate your opinion.

    Rebecca Rushton
    Esperance Podiatry & ENGO Blister Prevention
  2. Rebecca:

    Here is a basic article to help get the discussion moving.:drinks

  3. Asher

    Asher Well-Known Member

    Thanks Kevin :drinks

    This doesn't say much about tape but let me point out a few things:

    The skin doesn't have to 'rub' against anything for a blister to form. Rubbing is an ambiguous term but most people mean one surface moves relative to another when they say rubbing. This definition of rubbing is the cause of abrasions.

    To prevent blisters you need to minimise shear. I can think of 4 ways to minimise shear:

    1) Alter your activity - so that shear episodes are less in magnitude or frequency
    2) Reduce pressure - pressure is a factor that can increase the magnitude of shear.
    3) Reduce bony movement - if shear is the stretching of soft tissue between the outer of the skin and the bone, then if the bone moves less, the soft tissue will stretch less (less shear)
    4) Reduce friction - that means make it more slippery so that the skin can move with the bone at an earlier point in time

    Padded insoles don't reduce friction. In fact, most have a very high coefficient of friction. But padded insoles, by increasing surface area and thereby reducing peak pressure, can reduce shear.

    So where does taping fit into the above 4 shear-reducing factors? Or is there another way of reducing shear?

  4. blinda

    blinda MVP

    Hi Rebecca,

    Interesting observation, you got me thinking...:drinks

    Correct me if I`m wrong, but I thought static friction (the resistance to prevent slide), as opposed to dynamic friction, is reduced by tape.

    Shear stress is the force that tries to make things slide. Shear strain is the resulting internal destruction/distortion, in the case of blister formation; loss of adhesion, cellular destruction with the resultant accumulation of inter and intra cellular fluid. I agree that the tearing of skin at the level of the spiny (or dermo-epidermal junction) layer is due to repeated shear stresses (beyond their zones stuff); however this shear is caused by frictional forces applied to the epidermis......I think :confused:

    I don`t have a great deal of time today, but I found these articles which you may find of interest;

    Influence of external forces (pressure and shear force) on superficial layer and subcutis of porcine skin and effects of dressing materials: are dressing materials beneficial for reducing pressure and shear force in tissues?

    A New Technology for Reducing Shear and Friction
    Forces on the Skin: Implications for Blister Care
    in the Wilderness Setting

    How To Manage Friction Blisters

  5. blinda

    blinda MVP

    Here`s another interesting article;

    Friction Induced Skin Injuries

    Taken from above;

    I would caution use of lubricants though, as moisture reduces strength/integrity of the corny layer and the first of the articles I posted earlier stated “Moisture increases the interface friction coefficients, therefore increasing the possibility of shear induced tissue damage”.

    This is taken from the second article;

    I guess it`s difficult to maintain the ideal temperature and moisture levels to prevent blisters. But, I reckon taping can reduce static friction, which in turn reduces shear.

    Just my thoughts.

  6. Asher

    Asher Well-Known Member

    Hi Blinda and thanks. You’ve got me thinking now!

    I totally agree with the first quote you highlighted.

    I’ve looked up some definitions and static friction is indeed the force that resists one object moving over another. So if a box is sitting on a bench and you give it a little push, if that little push doesn’t actually move the box along, then you can say that static friction kept it in place.

    In fact, this definition is what I take friction itself to mean (but that could just be me over-simplifying things).

    But when most people use the term friction, they actually mean rubbing / one surface moving over another / moving relative to another.

    So if you say blisters are caused by friction, when you actually mean rubbing, I have a problem with that. Because shear is produced before any movement happens between the two surfaces. In fact, when they move relative to one another, this actually stops shear. If you can get the two surfaces to move relative to one another at an earlier point in time, you can reduce shear.

    But if you say blisters are caused by friction and you mean static friction, then I’m fine with that.


    PS: Agree with your lubricant thoughts, they reduce the coefficient of friction (COF) short term but increase it longer term, plus the detrimental effect on the skin.
  7. Asher

    Asher Well-Known Member

    Getting back to taping, you say
    To reduce static friction between two surfaces, you need to reduce the COF between the two surfaces - you need to make it more slippery.

    Does tape do that? I don't think so (but I don't know so).

    BTW, to reduce shear as it relates to skin damage, you don't have to limit yourself to reducing COF at the skin-sock interface. You can reduce shear at another interface, like a sock-sock interface (in the case of double sock systems) or at the sock-shoe interface (in the case of Shearban and ENGO patches). Reducing the COF values at either of these interfaces will reduce the shear experienced by the soft tissue.

    In the case of tape, the material is actually adhered to the skin so you are expecting to reduce COF at the tape-sock interface. I have my doubts about whether this is actually the case.

    What the tape does do though is the adhered layer protects the outermost layer of the epidermis and prevents any of it from being rubbed off - it prevents abrasion. An abrasion is not a blister though.

    What do you think?

  8. Interesting thread

    I do wonder if the tape helps in stopping the separation of the layers and thus increases the skins resistance to blistering ?

    so instead of looking at the change/reduction of forces it might be an increased ability to tolerate the same forces ?

    does that make sense ?
  9. Asher

    Asher Well-Known Member

    Hi Mike,

    I can imagine that circumferential taping could minimise shear, but in regard to blisters and sport, circumferential taping is avoided due to increased foot volume with exercise.

    I'm no dermatology expert, but I can't see a piece of tape reducing shear, but I could well be wrong.

    To put some structure to some of the concepts discussed, this is how I see blister prevention:

    Blisters are a shear injury -> To prevent blisters you must reduce shear -> There are 4 ways to reduce excessive shear:
    1. Reduce shear cycle repetitions
    2. Reduce movement of the underlying bone
    3. Reduce peak pressure
    4. Reduce coefficient of friction
    Hopefully I've attached a table that shows where seven blister prevention strategies fit in to these shear-reducing

    Does taping fit in here or is there a 5th factor I've overlooked.


    Attached Files:

  10. blinda

    blinda MVP

    Rebecca & Mike,

    You both got me thinking, too much. Good points re: interfaces and increasing ability of tissues to tolerate the same forces.

    Anyway, my (incomplete) thoughts, thus far;

    Indeed. Also, from what I can gather, shear loading begins and peaks before movement or sliding begins. In other words;

    SF (Static Friction) = High friction force
    DF (Dynamic Friction) = Low friction force

    So, I would assume that more shear strain results from SF than DF. Which fits with your earlier statement; “Shear is soft tissue distortion. Shear occurs even if nothing rubs against the skin.”

    However, I also think that DF can lead to abrasion, that is; superficial scraping or wearing away. At least that is suggested in this paper;
    Fabric and Skin: Contact, Friction and Interactions

    Agreed. From what I understand, a lower friction coefficient indicates there is less resistance to sliding. Perhaps this is what the taping does?

    Ok, I`m confusing myself now; If high friction (static) forces prevent sliding (dynamic), up to a point, maybe the tape/interface is reducing DF (if DF can lead to abrasion) only, as shear forces appear to be remaining high, causing a blister, although there is no movement/rubbing, or indeed de-roofing, as observed by yourself? This would fit with Polliack & Scheinberg`s (2006) paper (in my previous post), which stated; “Few interfaces address friction and shear”. In fact, maybe the tape is retaining higher force in the tissues, but is within the tissues` tolerant zone, so sliding/abrasion does not occur, yet shear does.

    What do you think?

  11. efuller

    efuller MVP

    I've been trying to think of a time when I've gotten a blister that was in spot where there was not rubbing. I can't. Well I've seen a few patients with pemphigous, but that's different.

    Thinking of a blister under the hallux. When you push off there is a horizontal force between the ground and the proximal phalnx. All the tissues inbetween have to "transmit" this friction. The shoe has push/pull/slide relative to the sock which has to push/pull/slide relative to the skin, which has to push pull relative to the bone. My guess is that the tape/moleskin/second pair of socks create a better "sliding point" so that the surface of the skin doesn't have as much pull on it as it does without the intervention. If you are trying to make a cut while playing basket ball, for example, the horizontal forces are going to be the same and they all have to be transmitted. Perhaps the foot slides a lilttle farther and hits the side of the shoe. The side of the shoe could provide the force that allows the horizontal forces at the toe to reduce. The net horizontal force has to be the same.

    It makes me think that the distance of the slide of the skin is important in blister formation. The increased padding that you mention may reduce the distance of the slide. Just some thoughts.

  12. Asher

    Asher Well-Known Member

    Hi Eric,

    Have a look at the COF of some common materials used in podiatry (attached). Remember, the COF is always a measurement between two materials (so a material doesn’t have its own COF – its relative to another) so the standard is to measure against a cotton sock.

    Spenco’s COF (in dry conditions) is 0.50. Moleskin’s COF is 0.62. As a real-life comparison, an estimation of the COF of a cotton sock against a polished tile floor is in the vicinity of 0.20.

    Knowing this, it’s hard to imagine that sports tape has a low COF.

    The distance of the slide is all-important in preventing blisters. The lower the COF is, either at the skin-sock interface or the sock-shoe interface, the earlier the glide and the sooner the skin can move with the underlying bone ie: less shear.


    Attached Files:

  13. Asher

    Asher Well-Known Member

    Hi blinda, please be assured you're making my brain hurt as much as I'm making yours:wacko:

    I think we agree, but I’m not 100% sure we have our definitions right.

    But essentially, a high COF will keep two surfaces in stationary contact longer, requiring a larger force to make one move over the other, and lead to more shear.

    Getting them to move relative to one another sooner is the aim – an early glide. You do this by reducing the COF. If it’s a late glide not an early one (late because of a high COF), you’ve had more shear and plus the glide (rub) with a high COF and you’ll get a blister and an abrasion. If the same COF situation exists but there is no movement, you’ll suffer the same amount of shear (blister-causing) but no abrasion (ie: blister with roof intact).

    As far as definitions go, there are all sorts of definitions for friction (plus there are apparently different types of friction). I don’t know where to look for a definitive definition – I’m really not good with physics. But I’m not sure your definitions of static and dynamic friction can be right. You can have a low static friction force and you can have a high dynamic friction force.

    Here’s one I do know: the point at which one surface moves relative to another (where the force of friction is overcome) is called the Limiting Friction Load (LFL). I’m thinking this is relevant.

  14. blinda

    blinda MVP

    Maybe I have just confused matters, sorry. I should have listened more during physics at school, instead of going to the beach :eek:

    I agree the LFL is very relevant. As I understand it; LFL is the threshold of motion. Thus, different CoF`s between 2 surfaces alters the LFL.

    Can`t help but think the tape is an interface which alters friction (whether it is static or dynamic, I`m unsure) and maybe shear loading, by allowing earlier slide/glide.

    What I really should have asked at the outset was; What material is the tape?

  15. Here's been my experience from my years as a runner, experimenting with various methods of taping as a way to reduce blistering, and treating many blisters in the feet of other athletes over the past 30 years of treating athletes.

    1. Blisters occur in areas of the skin of the feet where there is increased pressure and will occur more commonly in areas where the epidermal thickness of the skin is reduced.

    2. Blisters occur more commonly during hot weather (which makes sense because friction and pressure combine to cause localized overheating of the skin which, in turn, causes blister to form).

    3. Tape or moleskin can be effective at reducing blistering and works best if the adhesive of the tape does not adhere to the area expected to blister (or already has developed a blister). In other words, if you put tape over a blister, make sure that the "hotspot" or area of current blistering does not have the adhesive from the tape sticking directly to it. This is accomplished by fitting a non-adhesive material over the "hotspot" or existing blister and then taping over it.

    My guess is that the therapeutic effect of tape or moleskin is to reduce the thermal load on the skin from the offending material rubbing on the skin either by reducing the coefficient of friction and/or by providing thermal insulation to the skin from the heat produced by the frictional forces. However, it is important also to not use too thick of a pad over the blister since this, in itself, may increase the pressure on the "hotspot" or existing blister.
  16. Asher

    Asher Well-Known Member

    Hi Kevin,

    Here are a few comments in relation to the points you’ve made.

    1a) Pressure is definitely a factor that increases soft tissue shear. Without pressure, there is no shear. That puts weightbearing areas and bony prominences at greater risk of blisters.

    1b) Blisters are actually more common in skin where the stratum corneum and granulosum (outermost layers of the epidermis) are thick ie: plantar and palmer skin. These two layers, which form the roof of the blister, are sturdy enough to remain intact in spite of the forces applied. Where the stratum corneum and granulosum are thinner and more mobile, these layers are more likely to be abraded at the time the blister cleft is developing in the stratum spinosum (Naylor, 1955; Sulzberger et al, 1966).

    So this again puts weightbearing areas at greater risk of blisters. And it puts other areas like the posterior heel and dorsum of the toes at more risk of an abrasion / de-roofed blister. But with tape in place, the de-roofing by abrasion can be avoided.

    2) Blister formation does increase with increased temperature. I’ve also assumed this was due to increased perspiration, as a moist in-shoe environment will lead to higher COFs (as opposed to very dry or very wet skin). But a blister is not a thermal burn.

    No doubt it gets hotter at the area of the blister or hotspot (precursor of a blister), but is this cause or effect? The in-shoe environment gets hot no doubt, but I doubt there are small localised hotter areas leading to thermal burn blisters. I can’t imagine that the skin at the site of the hotspot is any hotter than the skin adjacent to it or even probably quite a way from it, except for the effect of the mechanical damage it is incurring. To the best of my knowledge, a blister is a mechanical separation within the stratum spinosum, not a burn.

  17. Increased friction to skin ----> increased local heat to area of skin subjected to friction ---> thermal injury to specific area of skin subjected to friction and heat.

    Since when do burns not sometimes cause blistering of skin?

    We call these "preblisters" on feet "hotspots" for a reason.

    Here's a good project for you. Get a thermal camera, wear your tightest shoes and dance in them all night, and see if the areas of your feet that are most red and sore aren't also the same areas that are the warmest using the thermal camera on immediate removal of shoes.

    My bet? Blisters are caused by a thermal injury. This would be an interesting experiment to help determine the cause of blistering from tight shoes.
  18. Tkemp

    Tkemp Active Member

    Hi Asher,

    I noted you seem to have an affinity for ENGO Patches and therefore did a little search on the internet.
    It appears Esperance Podiatry - where you work - is the Australasian distributer of ENGO.

    Before I join in this thread I would just like to question if:
    this thread is for actual research and interest, or merely for your product promotion?

  19. Asher

    Asher Well-Known Member

    Hi Kevin,

    Of course burns cause blisters. I’m suggesting that the foot blisters commonly suffered by athletes and other active people are not thermal burns but more a mechanical separation. I realise the area will get hot, but I’ve assumed this is the heat generated by the response to the injury - the resultant inflammation. I don’t think the thermal camera will help make this distinction.

    Do you make a distinction between rubbing (the sock moving against the skin) and shear (the sock not moving against the skin)?

  20. Asher

    Asher Well-Known Member

    Hi Tkemp,

    I understand your concern. I disclosed my connection to the product I am involved with in what I believe to be the appropriate manner at the beginning of this thread. I know the treatment one can rightfully receive here if going about things in the wrong way and I certainly don't want that.

    I’ve been researching blister causation and management techniques for a while now and my understanding is different to that of what I perceive is the mainstream understanding of blisters. Discussing this is the purpose of this thread.

  21. And that brings me back to my point about the tape changing the way the skin acts and it´s resistance.

    maybe the tape reduces the ease at which the skin separates, through compression? and this the whole of the skin moves as one.

    But if thinking about that maybe tape cannot do that??

    Also ....... if we have calloused skin it tends not to blister , why is that?

    maybe if the answer to that is know the tape answer is easier to find?
  22. Asher

    Asher Well-Known Member

    Mike and blinda,

    Sports tape like elastoplast is the tape I refer to. I'd assume tapes like gaffa tape and Kinesiotex tape would have a lower COF - I assume that because they're more shiny and so probably more slippery.

  23. Rebecca:

    To me, it makes the most sense using physics and physiological principles, that "friction blisters" on the feet are caused by both the mechanical shearing forces and the thermal injury that results due to the local heat concentrations cause by these repetetive mechanical shearing forces.

    My belief is that if the skin were kept cool, by some other means, that the repetetive shearing forces acting on the skin would produce much less incidence of blistering. My experience is that wearing shoes in hot climates produce much more blistering, than doing the same activities in cold climates, which tends to support my hypothesis that friction blisters are, indeed, a type of thermal injury.

    As far as a separation of skin layers being somehow supportive of a purely mechanical phenomenon that cause "friction blisters" on the foot, separation of skin layers also commonly occurs in thermal burns that have no mechanical irritation to the skin.

    Therefore, unless you can provide me with some evidence that mechanical irritation to the skin, by itself, that also produces no increase in skin temperature will also cause "friction blisters" to occur, then I will go with the more logical biomechanical and physiological explanation of blister formation in "friction blisters" as being mostly due to a thermal injury that is, in turn, caused by repetitive shearing forces and the resultant local tissue heat build-up that occurs.
  24. Jo BB

    Jo BB Active Member

    Another product I find that really helps to prevent blister formation is the application of zinc oxide-rub into the dorsal and plantar surfaces and then apply a little more thickly inter digitally. Keeping the skin "dry" is important. Just for interest sake an old VFL player and his fellow team mates were always provided with cabbage leaf innersoles by there coach to prevent blister formation! May be related to the use by women suffering from mastitis?
    Kind regards
    Jo BB
  25. Asher

    Asher Well-Known Member

    I'll see what I can find out Kevin.

  26. blinda

    blinda MVP

    Very interesting thoughts. D`you know, despite the plethora of literature on blister prevention, there is relatively scarce evidence of blister formation/causality. This is quite a good description though and briefly explains how frictional forces of a lower magnitude produce callus instead of blisters;

    I still think tape can alter shear loading by reducing dynamic friction, which reduces (but doesn`t stop, hence an intact bulla) internal shear in deeper tissues. Here are a couple of quotes from the `Friction Induced Skin Injuries – white paper`, which I posted earlier;

    I can`t honestly say that I have found anything to support the notion that heat is the main causality, although it is obviously a significant factor. There is certainly an increase in temperature, but not sufficient enough to `burn` or cause thermal injury, to underlying tissue. A true burn to the epidermis triggers the release of cytokines and other inflammatory mediators at the site of injury, which then causes exudation of proteins and fluid into interstitial tissue. Whereas friction blisters appear to be caused by repeated frictional forces that result in a cleft at the level of the spiny layer due to mechanical fatigue, this cleft fills with a serum-like fluid due to hydrostatic pressure. So, whilst both manifest as fluid filled bulla, histologically, they are quite different.

    Joseph Knapik has published a few articles on the pathophysiology of friction blisters (This is a good one; FRICTION BLISTERS: PATHOPHYSIOLOGY, RISK FACTORS, AND PREVENTION) In another he wrote; “Blisters occur frequently especially in vigorously active populations. Studies using repetitive rubbing techniques show that blisters result from frictional forces that mechanically separate epidermal cells at the level of the stratum spinosum.” Knapik JJ, Reynolds KL, Duplantis KL, Jones BH. Friction blisters. Pathophysiology, prevention and treatment. Sports Med. 1995 Sep;20(3):136-47.

    I think the `Friction Induced Skin Injuries – white paper` has helped me to understand why Rebecca is reluctant to use the term friction. It states;

    I`m not so sure that removing the term friction with regard to blisters is necessary, as they are not the same as pressure ulcers....but then again, I haven`t been researching blister prevention.

    Do my ramblings make any sense?
  27. Asher

    Asher Well-Known Member

    Here are excerpts from two literature reviews on the role of temperature in blister formation.

    Firstly, from the same 1995 paper by Knapik et al that blinda refers to:

    "Skin temperature appears to be a minor factor in blister formation. Blisters form somewhat more rapidly when the skin temperature is higher but blisters also occur when the skin temperature is low. In experimental rubbing studies, local heat is produced and skin temperatures have been reported between 41 degrees Celsius and 50 degrees Celsius. However, friction blisters do not resemble second degree thermal burns either clinically or histologically."​

    I’m not sure of the relevance of the last sentence as second degree burns effect the entire epidermis and some of the dermis, so this to me, doesn’t rule out the possibility that a ‘friction’ blister is a thermal burn. The rest of the excerpt, while implicating heat as a relevant factor, falls short of suggesting a blister is a burn.

    Richie’s 2010 literature review How to Manage Friction Blisters. Podiatry Today. 23 (6): 42-48 refers to the role of temperature:

    “Skin temperature can affect susceptibility to blister formation. Researchers have shown that a temperature increase of 4 degrees Celsius will speed up the rate of blister formation by 50%. Another study showed that walking on a treadmill for six minutes increased pedal skin temperature by over six degrees Celsius.

    This heat buildup may be due to metabolic activity, hyperemic response and frictional force developing against the skin inside of the shoe. Vigorous exercise therefore will increase blister formation by increasing sweat output on the feet and raising skin temperature.”​

    Again, this suggests increased temperature is a relevant and present factor and that the rubbing force against the skin may be responsible for an increased local temperature, but falls short of suggesting the skin suffers a thermal burn.

    As luck would have it, Farina Hashmi and colleagues from the University of Salford have just published a paper that has measured skin temperature before, during and after experimental blister formation at the back of the heel: http://www.ncbi.nlm.nih.gov/pubmed/22891732

    Local skin temperature was recorded every 3 minutes for 30 minutes and hourly for 5 hours. The blister-inducing load was applied until a blister was formed, which ranged from 4 to 32 minutes. At blister formation, local skin temperature increased by between 1.7 and 9.9 degrees Celsius.

    “In our experiments, there are three possible factors that could have influenced skin temperature change whilst the skin was subjected to load application: 1) change in environmental temperature, 2) subcutaneous tissue thickness influencing the protective mechanisms against tissue damage and 3) skin vasodilation due to inflammation in response to the external loads applied. We were interested in understanding only the third and hoped to minimize the influence of the other two. These as well as the limitations of the study are discussed in the following sections.”

    “We assumed that heat and temperature change generated by pure surface friction was short lived, i.e. dissipated within a few seconds. This was visually apparent on live thermal imaging footage during pilot testing. Since the skin temperature increased after repeated applications of load it is reasonable to assume that a physiological inflammatory response was initiated and responsible for the recorded skin temperature increases. This demonstrates that our method quantified the pre- and post-blister physiological inflammatory changes that occur in response to external loads. Also, that these temperature changes were not due to superficial frictional heat nor changes in environmental temperature (for up to 30 min post blister).”​

    I've been in touch with Farina, she'll be getting back to me next week, in regard to her opinion of the possibility that heat build-up from friction may in some instances cause a thermal burn and that this may fully or partly be responsible for blister formation.

  28. Good stuff, Rebecca. Keep up the good work on this subject. I find it very interesting. Sounds like more research needs to done on the subject, though.:drinks
  29. Asher

    Asher Well-Known Member

    Hi blinda

    The White Paper by Antokel et (2012) is a very informative paper that has helped me understand the relevant definitions of friction, so thanks! The type of friction relevant to skin trauma is dry friction. However, this paper provides two different definitions for dry friction:

    These aren’t the same and it confuses me (not difficult). The first is an action, the second is a force. The first requires movement, the second doesn’t.

    I think it would help if there was a single term and definition for the friction pertaining to the forces around skin trauma. This appears to be dry friction and I favour more the second definition. I think it should be:

    Dry friction is the force that resists relative motion between two bodies in contact.

    Now for the definitions of static friction and dynamic friction. I agree with the importance for a distinction to be made between the two and I like the definitions given:

    My understanding is that blisters are caused by high static friction. Because this causes high shear within the stratum spinosum. But low static friction will not cause blisters. So quantifying the level of the force is important. You can't just say static friction causes 'x' because a degree of static friction will always be present.

    My understanding is that abrasions are caused by high dynamic friction. But low dynamic friction will not cause abrasions. For example, a low COF (slippery interface) will allow sliding motion without the stratum corneum and granulosum being rubbed off Again, quantifying the force is important.

    A few thoughts on the quotes from the white paper you highlighted:

    100% agreed, where static friction is high.

    Agreed, the relative movement would lessen shear. But abrasions can be avoided if the degree of dynamic friction is low (eg: low COF).

    I’m not convinced you need dynamic friction to produce blisters. My understanding is that you don’t need movement relative to the skin to cause blisters. Shear causes blisters and this peaks before movement. I think high dynamic friction is the force that de-roofs the blister (ie: abrasion).

    Although I feel like I know a lot about blister prevention, I do struggle with the physics side of things, particularly when it gets to the real nitty gritty, like definitions. So please if anyone can point out any holes in what I have written or can improve upon it, that would be very much appreciated.


    PS: Your ramblings make a lot of sense and are very helpful blinda.
    Last edited: Jan 26, 2013
  30. blinda

    blinda MVP

    Farina is one of my all time heros, be great if you can persuade her to join the party here.
  31. Here is the complete abstract of the paper Rebecca mentioned. Good to see Chris Nester is involved with this research since I consider this type of research very important clinically. If anyone has a complete pdf of this paper, I would love to read it. kevinakirby@comcast.net

    Looks like Hashmi et al performed the experiment I spoke about a few days ago, without having to have their subjects dance the whole night in ill-fitting shoes...:rolleyes:

    Like I mentioned earlier, blisters seem to be a type of thermal injury being associated with a signficant increase in local tissue temperature. The next research question should then become: Does cooling the skin locally during repetitive load application slow down or prevent the formation of blisters versus ambient temperature conditions versus hot temperature conditions?

    My guess is that you need not only mechanical irritation to the skin but also need to have an increase in tissue temperature in order to get formation of friction blisters.
  32. blinda

    blinda MVP

    Ditto. belinda@winchesterpodiatry.co.uk

    Maybe you`re onto something here, Kevin. I also think Rebecca`s attention to detail can only serve to promote further research in this field. This is all good stuff :drinks
  33. Rebecca and Colleagues:

    Let me see if I can provide some clarity to this subject of friction.

    First of all, here is a very nice article in wikipedia on Friction.

    Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.

    Dry friction resists relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into static friction ("stiction") between non-moving surfaces, and kinetic friction between moving surfaces.

    Kinetic friction
    is also known as dynamic friction.

    I don't know that this is the case. Static friction will produce no increase in heat since there is no movement of the two bodies against each other. Dynamic friction will produce great increases in heat since the two surfaces are rubbing against each other.

    Both static and dyamic (kinetic) friction of a shoe on the skin can produce tissue damage and friction blisters. However, it is much more likely that the increase in temperature of the skin will be greatest when there are the following conditions:

    1) increased shoe on skin pressures;
    2) there is sliding of the skin on the shoe under that pressure (when there is dynamic friction);
    3) there are warmer ambient environments that allow the skin to reach a critical threshold of temperature where tissue damage and blistering occurs.

    Now, it is also theoretically possible that static friction of the shoe on the skin alone (no sliding of the shoe on the skin) could cause increased internal skin shearing forces which, in turn, could cause tissue damage and lead to friction blisters. However, with static friction alone, there would not be near the magnitudes of localized increase in skin temperature that is known to be associated with the development of friction blisters and I would think that keeping skin temperatures cooler would greatly reduce the likelihood of friction blister development.

    Try an experiment, Rebecca (and others following along):

    Take the palms of your hands and press them as hard together as you can and then move them side to side against each other but only move them 2-3 mm back and forth so that the skin of each hand has lots of static friction (the skin of one hand does not move on the skin of the other hand) but has no dynamic friction. How much increase in skin temperature occurs? Minimal.

    Now, take the palms of your hands and press them as hard together as you can and then move them side to side against each other but, this time slide them 15 mm back and forth so that the skin of one hand actuallly slides on the skin of the other hand so that a condition of dynamic friction occurs (the skin of one hand does move on the skin of the other hand). How much increase in skin temperature occurs? A very large increase in local skin temperature results due to the large amount of heat energy produced.

    Now, which of these two conditions do you think will cause more blisters to form on the palms of your hands?

    A. Having only static friction on the skin, or,
    B. Having dynamic friction on the skin?

    My bet?...... The condition with dynamic friction will produce much larger increases in localized skin temperatures and more likelihood of friction blisters developing.

    I'm not convinced that static friction of the shoe on the skin, by itself, can produce friction blisters in most situations. Large magnitudes of shear stresses within the layers of the skin will occur with both static and dynamic friction conditions on the skin surface. The difference is that localized increases in skin temperature will occur much more rapidly during conditions of dynamic friction whereas, during conditions of static friction alone, the localized increases in skin temperature will occur much more slowly and may never reach the thermal threshold to cause friction blisters to form.

    Now, the question is whether mechanical rubbing of the skin, by itself, without an increase in localized skin temperature will cause friction blisters. My guess is that a large increase in internal temperature within the statum spinosum layer somehow weakens the molecular bonds in this layer of the skin which then allows the internal shearing forces present within this layer to more easily separate the molecular bonds and, as a result, cause a mechanical separation of these layers and, in turn, cause a friction blister.

    In other words, you first have to "cook" the skin a little to loosen it up enough to allow the skin layers to slide on each other more readily and more easily mechanically separate and cause a friction blister.

    Good discussion.:drinks
  34. blinda

    blinda MVP

    Hi Rebecca,

    Yep, certainly a plausible term. It simplifies, yet encompasses the complex pathophysiology of mechanical trauma to the epidermis, in relation to blisters.

    Yep, also with you on that one. Kinda. It`s the cut off point between high (peak shear loading) and low static and dynamic (sliding) friction we (actually, probably just `I`) have difficulty in defining and ascertaining.

    Indeed. Which is what i initially said, but then completely confused myself, by trying to think too hard (Women know your limits).

    Neither am I. Like I said earlier, I really don`t know whether it is the static or dynamic friction, or indeed a bit of both, that produces in-tact shearing blisters. The evidence, thus far, just aint out there.

  35. blinda

    blinda MVP

    NB.; not sure how I managed to duplicate Rebecca's quote in my last post. Should have checked before editing time lapsed.:eek:

  36. So tape acts as an isolation against heat produced inshoe?

    Not sure I buy that ???
  37. Mike:

    Tape could very well act to insulate the skin surface from some heat transfer in friction blister situations.

    Put some tape on your finger and then touch a hot object. Then remove the tape and touch the same hot object again. In which situation does your finger get hotter faster?

    The main effect of tape in reducing the occurrence of friction blisters is, likely, as follows:

    1) reduce the coefficient of friction between the shoe and the skin thus reducing internal skin shearing forces and reducing localized heat production from dynamic friction at skin surface,

    2) reduce the conduction of heat to the skin surface by partially insulating the surface of the skin from heat transfer.

    Any more ideas of the effects of tape?
  38. blinda

    blinda MVP

    Here is Dr Farina Hashmi et al `s paper (It`s available on the Wiley Online Library, so figured it`s ok to share) ;

    Attached Files:

  39. Not only sassy....but resourceful also!!;):drinks
  40. Sure it means you can hold it there for longer if hot, but hold it there for long enough and you will experience burn.

    I still believe the internal shearing forces reduced, which also explains why calloused skin does not blister.

    and heat is given by produce of the shear forces ...... ?

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