Foot Science

Your foot is not a useless slab. It's a machine.

The 26 bones, 33 joints, 3 arches and more than 100 muscles, tendons and ligaments, mostly wasted inside a modern cleat. Here is what the machine can do and what it takes to get them back online.

The five things a foot does

Take any one away and the others get worse at their job.

Your sole is a sensory organ

The skin under your foot is dense with mechanoreceptors that report pressure, texture, slip and surface angle to your nervous system continuously. That feed is part of how you stay upright. Researchers describe the foot as behaving like "a sensory system for postural regulation", and show that improving plantar feedback measurably improves balance.

Put a thick, stiff, cushioned slab between that skin and the ground and you attenuate the signal. The foot still works. It just works with less information.

Your sole is a sensory organ

The skin under your foot is dense with mechanoreceptors that report pressure, texture, slip and surface angle to your nervous system continuously. That feed is part of how you stay upright. Researchers describe the foot as behaving like "a sensory system for postural regulation", and show that improving plantar feedback measurably improves balance.

Put a thick, stiff, cushioned slab between that skin and the ground and you attenuate the signal. The foot still works. It just works with less information.

What it does

Reads pressure, slip and surface angle, hundreds of times a second.

Why it matters on the field

You plant on instinct instead of reacting after the fact.

What blocks it

Thick midsoles, rigid plates, and a loose fit that lets the foot slide.

Width is structure, not comfort

When you load your foot, the toes are meant to spread. That splay widens your base and lets two specific muscles work: abductor hallucis at the big toe and abductor digiti minimi at the little toe.

Those two are exactly where the difference shows up. Comparing minimally-shod men with conventionally-shod men, researchers found the minimally-shod group had larger abductor hallucis and abductor digiti minimi, and higher, stiffer arches. Abductor hallucis size predicted how stiff the arch stayed during walking.

A tapered toe box holds both muscles in a shortened position for every hour you wear it.

Width is structure, not comfort

When you load your foot, the toes are meant to spread. That splay widens your base and lets two specific muscles work: abductor hallucis at the big toe and abductor digiti minimi at the little toe.

Those two are exactly where the difference shows up. Comparing minimally-shod men with conventionally-shod men, researchers found the minimally-shod group had larger abductor hallucis and abductor digiti minimi, and higher, stiffer arches. Abductor hallucis size predicted how stiff the arch stayed during walking.

A tapered toe box holds both muscles in a shortened position for every hour you wear it.

The big toe

Anchors the inside of your base and drives the final push-off.

The little toe

Anchors the outside edge — the one you load when you cut.

Together

They turn your foot from a point of contact into a platform.

The arch is the spring of the catapult

Your three arches, working with the plantar fascia and the Achilles, form an elastic system. It compresses as you land, stores that energy, and returns it as you push off. Ker and colleagues measured it in Nature in 1987: the arch alone stores and returns roughly 17% of the mechanical energy of running. They described the foot as working like a rubber ball bouncing along.

The spring has an engine: your calf. Fukunaga and colleagues put ultrasound on walking legs in 2001 and found the calf working almost isometrically. Its fibers hold nearly still, anchoring the Achilles, while the tendon does the stretching and recoiling, like a catapult being drawn and released. And modelling of runners puts that recoil at up to three quarters of the positive work of the calf and Achilles together. Your calf is as big as it is because holding that tension against your whole bodyweight, stride after stride, is serious work.

A spring only works if it is allowed to deform and recoil. Support it artificially and you take load off the tissue — which also takes away the stimulus that keeps it strong.

The arch is the spring of the catapult

Your three arches, working with the plantar fascia and the Achilles, form an elastic system. It compresses as you land, stores that energy, and returns it as you push off. Ker and colleagues measured it in Nature in 1987: the arch alone stores and returns roughly 17% of the mechanical energy of running. They described the foot as working like a rubber ball bouncing along.

The spring has an engine: your calf. Fukunaga and colleagues put ultrasound on walking legs in 2001 and found the calf working almost isometrically. Its fibers hold nearly still, anchoring the Achilles, while the tendon does the stretching and recoiling, like a catapult being drawn and released. And modelling of runners puts that recoil at up to three quarters of the positive work of the calf and Achilles together. Your calf is as big as it is because holding that tension against your whole bodyweight, stride after stride, is serious work.

A spring only works if it is allowed to deform and recoil. Support it artificially and you take load off the tissue — which also takes away the stimulus that keeps it strong.

Landing

The arch flattens under load and stores elastic energy.

Push-off

It recoils and gives that energy back, free of metabolic cost.

Blocked

A rigid or heavily supported sole does the deforming for you.

Force leaves your body through your toes

The toes are not along for the ride. Measured across 160 people, they are in ground contact for about three-quarters of the stance phase, exerting peak pressures comparable to the metatarsal heads.

They are also trainable, and it shows up in performance. Seven weeks of toe-flexor strength training roughly doubled joint strength and added 6cm to a standing jump. Toe flexor strength correlates with vertical jump height. In collegiate American football players, toe-pushing force correlated with pro-agility and 3-cone times — but not with straight-line sprint. Cutting and planting, specifically.

This is where your foot meets everything above it. The toe joint is the last link between the big muscles generating force and the ground they push against — so a foot that cannot transmit force wastes what your hips produce.

Force leaves your body through your toes

The toes are not along for the ride. Measured across 160 people, they are in ground contact for about three-quarters of the stance phase, exerting peak pressures comparable to the metatarsal heads.

They are also trainable, and it shows up in performance. Seven weeks of toe-flexor strength training roughly doubled joint strength and added 6cm to a standing jump. Toe flexor strength correlates with vertical jump height. In collegiate American football players, toe-pushing force correlated with pro-agility and 3-cone times — but not with straight-line sprint. Cutting and planting, specifically.

This is where your foot meets everything above it. The toe joint is the last link between the big muscles generating force and the ground they push against — so a foot that cannot transmit force wastes what your hips produce.

Jumping

Toe flexor strength tracks with vertical jump height.

Changing direction

Toe-pushing force tracks with agility and 3-cone times.

Sprinting in a straight line

No measured relationship. We are not going to claim one.

Feet respond to load like any other muscle

Six months of ordinary daily activity in minimal footwear increased foot strength by an average of 57% — and that is from everyday wear, not from training.

In a separate randomised trial of 57 runners, simply walking in minimalist shoes was as effective as doing dedicated foot-strengthening exercises. Both groups gained muscle size and strength over eight weeks. The control group gained nothing.

That is what passive exposure alone buys you. Deliberate loading keeps going: seven weeks of heavy toe-flexor training roughly doubled joint strength in adults who were already on ordinary feet, and added 6cm to their standing jump.

Feet respond to load like any other muscle

Six months of ordinary daily activity in minimal footwear increased foot strength by an average of 57% — and that is from everyday wear, not from training.

In a separate randomised trial of 57 runners, simply walking in minimalist shoes was as effective as doing dedicated foot-strengthening exercises. Both groups gained muscle size and strength over eight weeks. The control group gained nothing.

That is what passive exposure alone buys you. Deliberate loading keeps going: seven weeks of heavy toe-flexor training roughly doubled joint strength in adults who were already on ordinary feet, and added 6cm to their standing jump.

Week 8

Measurable gains in intrinsic foot muscle size and strength.

Month 6

Foot strength up ~57%, from everyday wear alone.

The catch

Adaptation takes time you cannot skip. Injury is what skipping looks like.

0

Bunions found in a 1949 survey of 5,128 people who had never worn shoes.

A survey of that scale is not modern epidemiology, but zero is a striking number.¹⁴

Diving Deeper:
Bunions & the Big Toe

Hallux valgus is the medical name for the big toe bending inward.

Clinicians measure the hallux valgus angle: the bend where your big toe meets your foot. Past 15 degrees lies the bunion. It is not rare: 23% of adults have it, rising to 36% over 65, and women at more than twice the rate of men.¹⁰ Across half a million 3D scans, women's average angle ran higher than men's in every region measured.¹¹

Feet that never wore shoes tell the other half of the story. Children raised barefoot have higher arches and straighter big toes than shod peers of the same age and background.¹² Barefoot adults have wider feet, widest across the toes.¹³

The angle matters because the big toe is the last link in the drive chain. The power of every stride starts in your glutes and travels down through the quads, the calf and the foot, and all of it leaves your body through whatever is touching the ground at push-off. Mostly, that is the big toe. A toe that points straight can press the ground squarely and pass that force along. A toe bent inward pushes off its side, and energy built by the biggest muscles you have leaks away at the very last link.

The good news: splay is trainable. Give the toes room, load them, and optionally hold the space with toe spacers. The evidence supports spacers combined with exercise, not as a standalone fix, which is why ours ship pointing you at the training plan.

Ours are printed from your own foot scan: 3D-Custom Fit Toe Spacers.

Diving Deeper:
Bunions & the Big Toe

Hallux valgus is the medical name for the big toe bending inward.

Clinicians measure the hallux valgus angle: the bend where your big toe meets your foot. Past 15 degrees lies the bunion. It is not rare: 23% of adults have it, rising to 36% over 65, and women at more than twice the rate of men.¹⁰ Across half a million 3D scans, women's average angle ran higher than men's in every region measured.¹¹

Feet that never wore shoes tell the other half of the story. Children raised barefoot have higher arches and straighter big toes than shod peers of the same age and background.¹² Barefoot adults have wider feet, widest across the toes.¹³

The angle matters because the big toe is the last link in the drive chain. The power of every stride starts in your glutes and travels down through the quads, the calf and the foot, and all of it leaves your body through whatever is touching the ground at push-off. Mostly, that is the big toe. A toe that points straight can press the ground squarely and pass that force along. A toe bent inward pushes off its side, and energy built by the biggest muscles you have leaks away at the very last link.

The good news: splay is trainable. Give the toes room, load them, and optionally hold the space with toe spacers. The evidence supports spacers combined with exercise, not as a standalone fix, which is why ours ship pointing you at the training plan.

Ours are printed from your own foot scan: 3D-Custom Fit Toe Spacers.

0

Bunions found in a 1949 survey of 5,128 people who had never worn shoes.

A survey of that scale is not modern epidemiology, but zero is a striking number.¹⁴

No two feet are the same

Get your feet scanned

What 1.2 million scans show

Volumental, the scanner behind our foot scans, published an analysis of 1.2 million 3D foot scans. Among people whose feet are the same length, the middle 90% span 16 mm of width, and one stock width fits at most 40% of them. Most shoes are sold in exactly one width.⁷

And it shows up on real feet

Reviews of fitting studies find 63 to 72% of people in shoes that do not match their foot's length or width.⁸ Among people whose shoes mismatch their feet, 60% also have at least a half-size difference between their own left and right foot.⁹ Fit is not a detail of footwear. It is the product.

40%

The most people one stock shoe width can fit, within a single size⁷

72%

Of people wear shoes that do not match their foot's length or width⁸

60%

Of mismatched-shoe wearers also have different-sized left and right feet⁹

⁷ Analysis of 1,200,847 3D foot scans: a 16 mm width spread within a single size class; one width fits at most 40.1%. Jurca A, Žabkar J, Džeroski S. Sci Rep. 2019;9:19155. PMID: 31844106.

⁸ Systematic review of footwear fitting studies. Buldt AK, Menz HB. J Foot Ankle Res. 2018;11:43. PMID: 30065787.

⁹ Three New York City populations, n=235. Chen X, et al. J Foot Ankle Surg. 2011. PMID: 21616688.

Full reference list at the bottom of this page.

Going minimal has a ramp

The honest part of the pitch: your feet are probably not ready yet, and rushing this is how people get hurt.

The cautionary tale

In a 2013 study, 36 experienced runners moved to minimalist shoes over ten weeks — gradually, by design. MRI scans afterwards found increased bone marrow edema in 10 of the 19 who switched, against 1 of 17 who stayed in traditional shoes. On the scale used, the top score is a stress fracture.

That is not an argument against minimal footwear. It is an argument against arriving unprepared.

The cushioning trap

There is a second trap worth naming. Cushioning does not make you land softer. When researchers put runners in highly cushioned shoes, their legs stiffened on landing and impact loading went up — 10–12% higher at speed — not down. Years of that landing pattern are exactly what a transition has to unlearn. You do not get the warning until the damage is already done.

This is the entire reason the Foot Assessment exists. It puts a number on where your feet actually are, and gives you the ramp that matches it.

The cautionary tale

In a 2013 study, 36 experienced runners moved to minimalist shoes over ten weeks — gradually, by design. MRI scans afterwards found increased bone marrow edema in 10 of the 19 who switched, against 1 of 17 who stayed in traditional shoes. On the scale used, the top score is a stress fracture.

That is not an argument against minimal footwear. It is an argument against arriving unprepared.

The cushioning trap

There is a second trap worth naming. Cushioning does not make you land softer. When researchers put runners in highly cushioned shoes, their legs stiffened on landing and impact loading went up — 10–12% higher at speed — not down. Years of that landing pattern are exactly what a transition has to unlearn. You do not get the warning until the damage is already done.

This is the entire reason the Foot Assessment exists. It puts a number on where your feet actually are, and gives you the ramp that matches it.

Week 1

Short exposures, full recovery

Wear time measured in hours, not sessions. Everything feels fine at this stage — which is exactly why people overshoot.

Weeks 2–6

Load goes up, slowly

The window your 6-week training program covers. Some arch and calf fatigue is expected and is the point. Sharp or localised bone pain is not — that distinction matters more than any schedule.

Months 2–3

Training in them properly

Muscle size and strength are measurably changing by around week 8 in the trial data. Full sessions become realistic.

Month 6

Adapted

The +57% mark in the trial data, reached on everyday wear alone. Deliberate training keeps building from here.

Week 1

Short exposures, full recovery

Wear time measured in hours, not sessions. Everything feels fine at this stage — which is exactly why people overshoot.

Weeks 2–6

Load goes up, slowly

The window your 6-week training program covers. Some arch and calf fatigue is expected and is the point. Sharp or localised bone pain is not — that distinction matters more than any schedule.

Months 2–3

Training in them properly

Muscle size and strength are measurably changing by around week 8 in the trial data. Full sessions become realistic.

Month 6

Adapted

The +57% mark in the trial data, reached on everyday wear alone. Deliberate training keeps building from here.

6

Foot strength levels, from Foundations to Elite feet

The Foot Assessment scores your feet across foot condition, toe strength and mobility, squat and balance, puts you on a level, and hands you the 6-week training program written for it. Free, plus $100 off any pair of custom cleats or shoes.

Free Foot Assessment + $100 Off

6

Foot strength levels, from Foundations to Elite feet

The Foot Assessment scores your feet across foot condition, toe strength and mobility, squat and balance, puts you on a level, and hands you the 6-week training program written for it. Free, plus $100 off any pair of custom cleats or shoes.

Free Foot Assessment + $100 Off

Fair questions

I've been told I need arch support. What now?

Talk to a clinician who knows your history — we are not going to give you medical advice from a product page, and anyone selling you shoes who does should worry you.

What we can say is what the research describes: habitual footwear that restricts foot motion is associated with weaker intrinsic foot muscles and less stiff arches. That is an association across populations, not a diagnosis or a treatment plan for your feet.

How long before I actually feel a difference?

Trial data puts measurable changes in foot muscle size and strength at around eight weeks, and a roughly 57% strength gain by six months — from people simply wearing minimal footwear day to day, with no training programme at all.

Treat that as the floor, not the ceiling. Deliberate loading keeps producing gains well past it: seven weeks of heavy toe-flexor training roughly doubled joint strength in adults who were already walking around on ordinary feet. And a single isometric strength test says nothing about balance, control, or how much load your feet tolerate across a season — all of which keep developing for years.

Fit is immediate. Strength is a season. Capability keeps going.

How solid is this research, honestly?

Mixed, and we would rather tell you than have you find out. Sample sizes run from 15 to 57 participants. A 2025 systematic review of seven studies and 213 participants found consistent improvements in foot muscle volume, arch function, toe flexor strength and neuromuscular control — while explicitly flagging heterogeneous protocols, small samples, missing follow-up, and some studies showing morphological gains without matching functional gains.

Directionally consistent. Not settled. Every study we lean on is cited below with its PMID so you can read it yourself.

References

Curtis R, Willems C, Paoletti P, D'Août K. Daily activity in minimal footwear increases foot strength. Sci Rep. 2021;11(1):18648. PMID: 34545114.

Ridge ST, Olsen MT, Bruening DA, Jurgensmeier K, Griffin D, Davis IS, Johnson AW. Walking in minimalist shoes is effective for strengthening foot muscles. Med Sci Sports Exerc. 2019;51(1):104–113. PMID: 30113521.

Holowka NB, Wallace IJ, Lieberman DE. Foot strength and stiffness are related to footwear use in a comparison of minimally- vs. conventionally-shod populations. Sci Rep. 2018;8(1):3679. PMID: 29487321.

Ker RF, Bennett MB, Bibby SR, Kester RC, Alexander RM. The spring in the arch of the human foot. Nature. 1987;325:147–149. PMID: 3808070.

Fukunaga T, Kubo K, Kawakami Y, Fukashiro S, Kanehisa H, Maganaris CN. In vivo behaviour of human muscle tendon during walking. Proc Biol Sci. 2001;268(1464):229–233. PMID: 11217891.

Lai A, Schache AG, Lin YC, Pandy MG. Tendon elastic strain energy in the human ankle plantar-flexors and its role with increased running speed. J Exp Biol. 2014;217(17):3159–3168. PMID: 24948642.

McKeon PO, Hertel J, Bramble D, Davis I. The foot core system: a new paradigm for understanding intrinsic foot muscle function. Br J Sports Med. 2015;49(5):290. PMID: 24659509.

Jurca A, Žabkar J, Džeroski S. Analysis of 1.2 million foot scans from North America, Europe and Asia. Sci Rep. 2019;9:19155. PMID: 31844106.

Buldt AK, Menz HB. Incorrectly fitted footwear, foot pain and foot disorders. J Foot Ankle Res. 2018;11:43. PMID: 30065787.

Chen X, et al. Foot and shoe size mismatch in three different New York City populations. J Foot Ankle Surg. 2011. PMID: 21616688.

Nix S, Smith M, Vicenzino B. Prevalence of hallux valgus in the general population: a systematic review and meta-analysis. J Foot Ankle Res. 2010;3:21. PMID: 20868524.

Hughes J, Clark P, Klenerman L. The importance of the toes in walking. J Bone Joint Surg Br. 1990;72(2):245–251. PMID: 2312564.

Goldmann JP, Sanno M, Willwacher S, Heinrich K, Brüggemann GP. The potential of toe flexor muscles to enhance performance. J Sports Sci. 2013;31(4):424–433. PMID: 23106289.

Yamauchi J, Koyama K. Importance of toe flexor strength in vertical jump performance. J Biomech. 2020;104:109719. PMID: 32173032.

Yuasa Y, Kurihara T, Isaka T. Relationship between toe muscular strength and the ability to change direction in athletes. J Hum Kinet. 2018;64:47–55. PMID: 30429898.

Ridge ST, Johnson AW, Mitchell UH, Hunter I, Robinson E, Rich BSE, Brown SD. Foot bone marrow edema after a 10-wk transition to minimalist running shoes. Med Sci Sports Exerc. 2013;45(7):1363–1368. PMID: 23439417.

Zech A, Argubi-Wollesen A, Rahlf AL. Minimalist, standard and no footwear on static and dynamic postural stability following jump landing. Eur J Sport Sci. 2015;15(4):279–285. PMID: 25010996.

Viseux F, Lemaire A, Barbier F, Charpentier P, Leteneur S, Villeneuve P. How can the stimulation of plantar cutaneous receptors improve postural control? Neurophysiol Clin. 2019;49(3):263–268. PMID: 30639034.

Kulmala JP, Kosonen J, Nurminen J, Avela J. Running in highly cushioned shoes increases leg stiffness and amplifies impact loading. Sci Rep. 2018;8(1):17496. PMID: 30504822.

Rodríguez-Longobardo C, Gómez-Ruano MÁ, Canosa-Carro L. Effects of barefoot and minimalist footwear strength-oriented training on foot structure and function in athletic populations: a systematic review. J Clin Med. 2025;14(21). PMID: 41227025.

Jiao Y, Džeroski S, Jurca A. Analysis of hallux valgus angles automatically extracted from 3D foot scans. Ergonomics. 2023;66(8):1164–1175. PMID: 36269073.

Hollander K, et al. Growing-up (habitually) barefoot influences the development of foot and arch morphology in children and adolescents. Sci Rep. 2017;7:8079. PMID: 28808276.

D'Août K, et al. The effects of habitual footwear use: foot shape and function in native barefoot walkers. Footwear Sci. 2009;1(2):81–94.

Shulman SB. Survey in China and India of feet that have never worn shoes. J Natl Assoc Chiropodists. 1949;49:26–30.