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Perth Podiatrist FAQ – Are You Too Fat for Your Plantar Fascia?
Heel Pain , Sports Podiatry

Perth Podiatrist FAQ – Are You Too Fat for Your Plantar Fascia?

August 03, 2018

Is Your Weight Causing Your Plantar Fascia to Tear?

It’s a question I get a lot being a Perth Podiatrist, so today I’m going to quickly and effectively demonstrate that you’re not too fat for your feet & plantar fascia…or if you are what you can do. Besides, you know – lose weight. Now before I get done for hating fat people let me premise this blog by mentioning that up until the last years of uni I was 120kgs ….of fat, not muscle. I’ve always been the fat kid growing up, so I find it to be an extremely lazy finding of people to say: “you need to lose weight” for “such and such” health benefits. So eat your dessert now because you’ll need your energy to read on.

Don’t worry plantar fasciitis and its associated heel pain can be quickly and effectively treated by our Perth Podiatrist at Foot & Leg Podiatry, and our Perth clinics are easy to find. If you’re suffering from heel pain then isolating the presence of plantar fasciitis and beginning targeted treatment is paramount. Professional advice should be sought and our Perth Podiatrist regularly treats patients concerned about plantar fasciitis so you can rest easy knowing your feet are in safe hands. An appointment at our podiatry clinic is only a phone call or web enquiry away and no referral is required, making it easier than ever to find a solution to your plantar fasciitis and associated heel pain problems.

Disclaimer: This is simply a general discussion regarding how much force it would take to tear your plantar fascia by our Perth podiatrist, using the latest research on plantar fasciitis. Any advice & information is general in nature and not to be taken over the advice of a qualified medical professional who is aware of your specific injury details. I hope this blog inflames your interest in the topic – pun intended, so without further delay let’s find out more about tearing your Plantar Fascia:

Force = Mass x Acceleration: 

First, a physics recap – Newtons are a standard unit used in physics to measure force. But saying someone weighs 200 newtons isn’t easily relatable so to make this information easier to understand I’m simply going to be translating the units to kilograms (kgs) because most people know how much they weigh and the difference between 1kg and 100kgs.

Now on Earth, this is pretty easy to do – we simply divide the force measured by 9.8 (rough acceleration of gravity) to get the mass that would create the measured force.

How Strong is My Plantar Fascia?

In a literature review published in Sports Medicine, Scott et al identified that cadaver studies completed to date have measured the plantar fascia failure load (force to tear) to be between 900 and 1550 newtons of force. To put it in normal numbers that’s between 91.8kgs to 158.2kgs of force that it would take to tear apart your plantar fascia.

I was actually surprised by those numbers because I instantly thought – “Oh My GOD – I weigh over 91.8kgs!!”.

Am I at risk of tearing my Plantar Fascia?

If you weighed over 91.8kgs, had only 1 foot to walk with that somehow had your whole body weight attached such that it was hanging from your plantar fascia and had no muscles to help out then yes based on the studies findings…you’re going to tear your plantar fascia…but that’d probably be the least of your problems.

Your Weight is Just One SMALL Factor Contributing to Plantar Fasciitis & Heel Pain.

Yes you might weigh 91.8kgs or you might even weigh over 158.2kgs but you need to remember that you have 2 legs to walk on (running is the only time you effectively ‘stand on one leg’ when moving) so double that weight or keep it the same if you’re running. Then remember your weight doesn’t hang from your feet, it actually pushes down on an arch structure your foot bones form which in turn stretches your plantar fascia…as well as the plethora of intrinsic foot muscles and extrinsic foot muscles which also support different parts of your foot’s arch, to slow its collapse.

Plantar Fasciitis & Heel Pain is all about your Lower Limb Biomechanics and Foot’s Arch.

Why is my foot’s arch so important? Because its engineering saves your plantar fascia and supporting arch muscles from taking the full weight of your body with each step forward. If we look at a simplistic arch force diagram and pretend you are running so your whole body weight is going through one foot with force labelled (P) and your foot is the average length of 170mm (plantar fascia length NOT toe-tal foot length) labelled (L). Assume your arch height is around 30mm. And you’re left with a pulling force labelled (Pull F).

Pull F = 15 x 900 x 170 / 64 x 30 = 1195N = 121.2kgs of force (but wait…that’s more tension then my bodyweight?!) HOW AM I STILL RUNNING?!

Your Foot Muscles Matter!

Don’t worry, I’m as surprised as you are about the above revelation and am seriously reconsidering running a marathon – thankfully I’m married to a structural engineer so pairing my expert knowledge of anatomy (remember it’s my blog) and her expert knowledge of structural analysis together we have come up with a solution to ‘soften the impact’. See when you’re dealing with an arch apparently the deepest structures take the weight first and then their failure or stretch (for muscles/ligaments) allows the next level to take over and so forth.

Are My Foot Muscles Taking More Force than My Plantar Fascia?

Using the above dimensions and since your deeper arch muscles have a shorter length to work across – being higher (estimate 10mm higher) up in the arch the force they’re under is actually far greater. To accurately work out the above was too complex and put me to sleep writing this so for the purposes of this blog, I’m making up rough figures so you don’t need more sugar to fuel your brain cells because right now I’m thinking that a diet sounds great for your plantar fascia:

Assume L = 130mm (40mm off the 170mm total arch L)

Assume H = 20mm (10mm higher up the arch)

Pull F = 15 x 900 x 130 / 64 x 20 = 1371N = 140kgs of force. Yes your poor intrinsic foot muscles. That’s 20kgs more weight they need to deal with!

So I Should Actually be Worried about my Foot Muscles?

Bingo. But there are 4 layers of your foot and there are more muscles per layer to handle this force so divide that number by the number of muscles in the layer. In the first layer (most superficial) = 3, in the second layer (deeper layer) = 7, in the third layer (deeper layer again) = 4 and in the fourth layer (deepest, but technically in between the bones so doesn’t really count) = 5. So dividing 140kgs by 5 = 28kgs of force per foot muscle 

The Way You Use Your Foot Muscles is Also Important. 

We’re not talking about bicep curling 28kgs here. No, your muscles are actually being pulled apart when you walk or run, which is a LOT easier on your muscles. This means they don’t need to be that ‘strong’ or act for that long because each step when you’re running lasts for at most 1 second (unless you’re walking very slowly). But the damage can still be done!

Remember that Muscles Can Move & Stretch!

The beauty of loading up foot muscles is that as each layer ‘gives up’, the muscles involved can stretch and allow the next muscle layers to take the strain and give them some rest. It’s when this rest period isn’t long enough that intense & lasting heel pain or plantar fasciitis sets in. This is a LOT harder than it seems to be to do – I believe it takes at least 6 months of consistent foot pain as a starting point for a potential plantar fasciitis injury if you’ve continued to walk on a painful foot without rehab.

Rehab’s an Option for Foot Pain Caused by Plantar Fasciitis?

Everyone tells me they have plantar fasciitis, yet when I test their plantar fascia – you guessed it – NO PAIN. No, I’m not a miracle worker or even Perth’s Best Podiatrist – even though I’ll try to be one day… I actually simply test the different layers of the foot to identify which layer your problem is in. I then come up with a treatment plan for your feet and legs from there. It’s that simple – that doesn’t mean it’s easy though.

So Am I Too Fat For My Plantar Fascia?

No. If you weigh over 91.8kgs or even over 158.2kgs and like to go for 30 minute runs every day without a rest day or two and have been experiencing foot pain for at least 6 months without seeking professional health care – or a Perth Podiatrist then maybe you’ve been tearing your plantar fascia. But even with all this, I’ve never seen a full or even full-thickness partial tear in a plantar fascia. Don’t try to be my first!

What Should I Do If I Am Concerned About Plantar Fasciitis?

If you do have a painful heel problem and are concerned that plantar fasciitis could be the culprit then consulting a Perth Podiatrist who can expertly evaluate, examine and if the necessary image and treat your plantar fasciitis heel pain quickly and effectively will lead to your best outcome. An appointment at our Perth podiatry clinics is only a phone call or web enquiry away. No referral is required, making it easier than ever to find a solution to your plantar fasciitis and associated heel pain problem.


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Rino Saint

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