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Friction, too much friction | What's the key to socks that prevent blisters?

Friction, too much friction | What's the key to socks that prevent blisters?

Reducing hot spots, blisters and irritation on our feet is crucial, not just when you are running or hiking but throughout the day, in business shoes, work boots or your casual kicks.

With the main function of a sock being to act as a barrier between your skin and a shoe to protect it from scrapes, pressure and blisters, it's important to choose right. Do you need material that is moisture loving or not? Should your socks be thick or thin? Is wool too warm for hot weather? We're going to delve in to answer these and maybe bust a few pre-conceptions.

Getting blisters or hot sports is highly influenced by the fabric composition of the socks you wear. This is because different sock fibers, have differing friction coefficients, which basically means how much friction or resistance the fiber creates.

To add complicate it a little further, the friction characteristics change based in different conditions and when your socks get wet or sweaty, certain fiber can really excel. So let's have a quick look at what the key fiber's are in socks that prevent blisters.

Friction, too much friction

The key is to reduce friction. less friction means less red skin and blisters.

Cotton:

Cotton is a very sustainable fiber but for socks, particularly sports socks, has high friction and tends to deform and pill as it dries, leading to blisters and the sock often becoming stiff and losing shape. This is why you usually only see cotton used in casual socks.

Acrylic:

Acrylic fibers have shown to have the highest frictional forces under all conditions. Acrylic is a time of fiber made from plastic polymer fibers similar to nylon, polyamide, coolmax etc. Pertroleum based fibers such as these are often the material of choice for a lot of sports socks due to their moisture wicking and hydrophobic (doesn't absorb moisture) properties, but they seem to have greater friction as well as more fabric deformation when wet.

Wool:

Fine wool has less frictional force that acrylic fibers

When comparing acrylic fibers to wool, wool has significantly less frictional force and in a lot of research is a clear favourite. (1,2)

This is summed up nicely in a research paper done at Otago University (Van Amber et al., 2014) that looked into the effect of fiber type of frictional characteristics in socks:

 

"The most important effect of fiber was on the static frictional force and coefficient of static friction of damp fabrics, with fabrics composed of fine wool exhibiting lowest friction, and acrylic fabrics the highest."

 

Weight:

Heavier weight socks lead to about double the frictional force of light weight socks, irrelevant of the fiber type in your sock. The key is not to aim for a super thick sock but a sock with high quality fibers with low friction that form a thin membrane over your skin.

Moisture:

You can group sock fibers into two groups.

1. Hydrophobic Fibers, which do not absorb much moisture, which means excess moisture is drawn through the fabric and can then be wicked away but it doesn't absorb it off the feet and due to the moisture repelling hydrophobic properties, tends to only wick away excess. The main fibers you know that do this is your plastic fibers such as polyamide and CoolMax.

2. Hydrophilic Fibers, which absorb moisture. Examples of this are cotton and wool. There is a difference between these two fibers though as wool has some intricacies that help sheep adapt to various temperatures and conditions.

Merino wool actually has a hydrophobic outer that repels water and a hydrophilic (moisture loving) inner which absorbs water vapor. This moisture absorbing cortex can absorb up to 1/3 of it's weight while still feeling dry on your skin. This all means that this super fiber can absorb a heap of perspiration while also feeling drier than other fibers due to it's hydrophobic, dry, other later.(3,4)

This great wicking ability of wool makes wool socks not just ideal for cold temperatures but also ideal for warm temperatures too!

Merino wool moisture wicking properties

 

Conclusion:

Fine wool fiber and yarn creates less friction and so helps to reduce the incidence of blisters. When the fabric is wet, it performs even better when compared to acrylic type fibers and is also less likely to deform. For reducing blisters and avoiding too much friction, chose socks with merino wool that form slim, membrane like protection over your feet. For EVEN MORE blister protection, choose toe socks, which wrap each separate toe in a protective membrane.

 

Why are our socks a blend, not 100% merino?

We chose to commit to having at least 50% of our composition made with Merino yarn. Other than the sustainability aspect of using a renewable fiber, our main priority was performance and keeping you comfortable and blister free all day, whether you're battling hot muggy conditions, cold and wet weather or dry heat.

We found  a blend of fibers gets the best of both worlds. Fine merino yarn for moisture and temperature regulation, reduced deformation and less friction but also polyamide (nylon) for strength and resilience and spandex for further elasticity and reduced slippage. Research has also shown that a blend with 50% merino was best over a long hike as well as showing that when compared to socks with no wool, they had more dry spots, and stored about 3 times more moisture.

 

 

Orthotics VS Foot Strengthening: Do you need to rely on arch support long term?

orthotics or foot strengthening

Do you need to rely on orthotics long term after injury or even if you have flat feet? There’s a good chance that you don’t, but only if you are up to the task of foot strengthening

Orthotics are widely used as the go-to treatment for foot, ankle and knee pain, but should they be relied on long term? Let’s look at the alternatives and how they stack up! As a Physio, I find orthotics hugely useful in helping with lower limb over-load injuries such as:

  • Achilles tendinopathy
  • Plantar fasciopathy (plantar fasciitis)
  • Runner’s knee

BUT the majority of the time as with anything external such as a brace, strapping and more, they should not be a long term fix. They do help guide movement and they do help ease pain which is brilliant short term, but they don’t create lasting change to your tissue.

So, what is the alternative?

The big one is to focus on improving your foots function, strength and resilience so that extra support isn’t needed in the long term. Think of it like improving your bodies ability to control motion rather than relying on something external to do it, in the long term.

Progressively load your foot and it can adapt and improve to be able to handle more and more – as long as that loading is smartly progressed, and good recovery time given. Foot strengthening isn't a quick fix, but it certainly is a bit part of the long term fix for foot pain, injuries and reliance on supports.

But does the research back this up?

Can you work towards ditching your orthotics, or even reliance on bulky stabilizing shoes?

A study was done that compared the effect of foot strengthening exercises with orthotics and how that changes the weight bearing arch height. They measure this with the navicular drop test which measure how much your medial arch drops lower when standing compared to sitting.

They found that that there was a significant improvement in the group that did the foot strengthening exercises for 6 weeks compared to no difference in those that just used insoles. As a huge bonus the group in the study that did the foot exercises also improved their balance scores by over 10%. Keep in mind that even though they found a significant difference, it wasn’t a large study size so take it with a grain of salt.

To back that up, HERE is a larger study that showed orthotics have no benefit over exercise rehab in the treatment of anterior knee pain (runners knee).

Yet another study, this time a systematic review, found a similar result in that the outcome for those with knee pain in this case when comparing orthotics to strengthening (of the hip as this partly controls the leg rotating and hence foot pronation) that there was no difference between the two.

So all in all, there is a lot of research on the effect of orthotic use but not a lot on the effect of exercises to improve arch control and resilience. The studies that are available though show either a similar effect between the two treatments or more improvements with exercises.

That gives us a good idea of what we can do to get the same if not better effect as orthotics and it’s a great long-term option!

#exerciseismedicine

What if I have flat feet?

Firstly, there isn’t a lot of strong evidence that having a lower arch (flat feet) is a big issue as it doesn’t have a strong correlation with injury across the research. Most research has shown that there is a relationship between both high and low arch height and lower limb injuries but the relationship is fairly weak

In terms of pain associated with flat feet, then there is some really cool research on this. One is a good sized meta analysis (Hoang et.al. 2021) done this year and to sum it up, it showed:

Exercise alone OR combined with orthotics has better effects on pain that orthotics alone. They showed clearly that active intervention (strengthening) had better result that passive treatment options. They also showed that neither treatment changes foot alignment or foot posture but this isn’t often needed as it’s not about having the perfect foot posture but having the capacity of your soft tissues to control motion and absorb and release energy/shock.

 

Conclusion

Orthotics don’t improve your intrinsic tissue capacity to handle load and actually are a risk factor for injury in runners. They are definitely useful but best when used as a stepping stone while you work on improving your foot and legs mobility, strength and overall resilience – which takes time and patience. The same goes for if you have flat feet, you can improve your capacity to handle and control load and therefore you will have less reliance on passive supports and you can gradually free your feet!

 

Free your feet and Subscribe to our blog for regular info, advice and rehab exercises relating for our brilliant feet.

 

Disclaimer: This is not medical advice and If you have orthotics – don’t go throw them out and go cold turkey. If you do want to ease away from relying on them you need to work on building strength, control and mobility first and then progressing away from them, ideally under the guidance of a Physio.