Why barefoot sand walking is a foot strength program in disguise

Why your feet are weak — the shoe-cushioning story

Modern shoes are remarkable engineering. They are also, for most adults, a kind of cast. A typical cushioned trainer adds 20 to 30 millimetres of foam beneath the heel, a stiffened midfoot shank, and an upper that holds the toes in a narrow box. The foot inside that envelope does very little work. The arch is supported externally, so the muscles that should support it from within go quiet. The toes cannot splay, so the small muscles that splay them lose tone. The heel lands on foam, so the spring-like collagen of the plantar fascia is unloaded.

Over years, this produces what Patrick McKeon and colleagues called the "foot core" deficit in their influential 2015 paper in the British Journal of Sports Medicine. They argued that the foot has a local stabilising system — the intrinsic muscles — directly analogous to the deep stabilisers of the lumbar spine, and that this system is routinely ignored in rehabilitation and training. When it weakens, load transfers up the kinetic chain. Plantar fasciitis, posterior tibial tendinopathy, medial tibial stress syndrome and even some knee pain patterns become more likely.

The shoe is not villainous. It is simply doing the work your feet were built to do, and your feet, like any unused tissue, adapt by getting smaller and weaker.

Foot intrinsic muscles 101 — what's atrophied

The intrinsic foot muscles sit entirely within the foot itself. There are roughly 20 of them, arranged in four layers on the plantar side plus a small group on the dorsum. Functionally, the important ones for arch support and toe control include the abductor hallucis, flexor digitorum brevis, quadratus plantae, the lumbricals, and the flexor hallucis brevis. The extrinsic muscles — tibialis posterior, tibialis anterior, the peronei, the long flexors and extensors — originate up in the leg and send tendons down across the ankle.

Glen Lichtwark and Luke Kelly's imaging and EMG work, published across several papers in the Journal of the Royal Society Interface and the Journal of Experimental Biology, has shown that these intrinsics are not passive struts. They actively modulate arch stiffness during the stance phase of walking and running. When the intrinsics are anaesthetised, the medial longitudinal arch collapses more under load and the foot becomes a less efficient lever. The implication is straightforward. A strong foot is a stiffer, springier foot. A weak foot is a floppier, more energy-leaking one.

The catch is that you cannot easily see or feel an atrophied abductor hallucis the way you can see a thin quadriceps. The deficit shows up as poor single-leg balance, a toe that drifts toward the second toe over decades, or an arch that fatigues on long walks. Most people do not notice until something further up the chain starts to hurt.

What sand actually demands of foot muscles

Sand is an unstable, deformable surface. Each footstrike compresses and shears the grains, which means the foot lands on a target that moves under it. To stabilise, the intrinsics must fire harder and longer than they do on pavement. The toes grip. The arch must actively resist collapse because there is no firm ground to bounce off. The peronei and tibialis posterior work overtime to control inversion and eversion as the surface tilts unpredictably.

On dry, deep sand, the foot also sinks. To pull it back out and swing it forward, the tibialis anterior — the muscle running down the front of your shin — has to dorsiflex against a heavier, more resistant load. This is the same muscle that is famously underdeveloped in seated, shoe-clad populations and famously sore the first time someone tries sled drags or backwards walking.

Yuki Hashimoto, Yasushi Sakuraba and other Japanese sports-science groups have studied sand training in athletes for decades, originally in beach volleyball and soccer pre-season conditioning. Their consistent finding is that sand alters the muscular cost of locomotion without changing speed much. You move at a similar pace and feel like you are working considerably harder, because the surface is doing a kind of invisible resistance training on the foot, calf and hip.

The data on sand-walking energy cost

The cleanest numbers come from two studies. Timothy Lejeune and colleagues, writing in the Journal of Experimental Biology in 1998, compared the mechanical and metabolic cost of walking and running on hard ground versus dry sand. Their headline result: walking on sand cost roughly 1.6 to 2.5 times more metabolic energy than walking on a firm surface at the same speed, and running on sand cost about 1.6 times more. They attributed most of the extra cost to mechanical work done against the deforming surface and to reduced elastic energy recovery from the muscle-tendon units.

Adrian Pinnington and Brian Dawson, in a 2001 paper in the Journal of Science and Medicine in Sport, found a similar pattern in trained runners. Oxygen consumption at a matched submaximal running pace was about 1.6 times higher on soft sand than on a grass surface, and heart rate climbed accordingly. They noted that the metabolic premium was paid primarily by the muscles of the lower leg and foot, not by a generalised whole-body cost.

For our purposes — a foot strength program — the practical reading is this. Forty minutes on dry sand is metabolically and mechanically closer to sixty-plus minutes on pavement, and the extra load lands disproportionately on the foot intrinsics, dorsiflexors and calf. You are doing a focused lower-leg training session that happens to look like a walk.

Building a beach foot-strength progression

A sensible progression respects two facts. First, the tissues of the foot have not been loaded like this in years or decades. Second, the calves and tibialis anterior will be the first to complain, usually within 24 to 48 hours.

Begin with 20 minutes of barefoot walking on wet, firm sand at the water's edge two to three times per week. Wet sand at low tide compresses far less than dry sand, so it is closer to a firm trail in mechanical cost. This is your acclimatisation phase. Expect mild calf and arch soreness for the first week or two. Stop and put shoes back on the moment you feel a hot spot or sharp pain anywhere — sharp is not the same as muscular fatigue.

In weeks three and four, extend to 30 to 40 minutes and start mixing in five-minute segments on drier, looser sand higher up the beach. The metabolic and muscular cost jumps noticeably on dry sand. Keep the dry-sand portion short until your feet tell you they are ready for more.

By weeks five through eight, you can build to 45- to 60-minute sessions that alternate wet and dry sand in roughly equal proportions. At this point most people notice their single-leg balance has improved, their toes splay more naturally, and their arch fatigues less on long walks in regular shoes.

This is a long, slow build by design. Daniel Lieberman and colleagues at Harvard, in their work on barefoot and minimal-shoe running published in Nature in 2010, repeatedly emphasised that the transition is the dangerous window. Tissue adapts on a timescale of weeks for muscle and months for tendon and bone. People who skip the slow phase get metatarsal stress reactions and Achilles tendinopathy.

The barefoot-running mistake (skipping the walking phase)

The most common error in minimal-footwear practice is to read a book about barefoot running, buy a pair of zero-drop shoes, and start running. The injury rate when this is done abruptly is well documented. Sarah Ridge and colleagues at Brigham Young University, publishing in Medicine and Science in Sports and Exercise in 2013, found a notably higher rate of bone marrow oedema in the metatarsals among runners who transitioned quickly to minimal shoes compared with matched controls in conventional trainers.

The fix is not to abandon minimal footwear. The fix is to spend months walking before you run. Barefoot walking on sand is, in this framing, a near-ideal preparatory dose. The forces are lower than running. The surface is forgiving. The intrinsics and dorsiflexors get loaded without the impact spikes of asphalt. Several months of progressive sand walking gives the foot tissues something they almost never get in a modern adult life: a slow, sustained, weight-bearing strength stimulus.

If you do eventually want to run barefoot or in minimal shoes, the literature suggests treating walking as a 12-to-24-week prerequisite, not a warm-up.

Sand quality and Wasaga: dry-deep vs wet-firm

Wasaga Beach is roughly 14 kilometres of fine freshwater sand on the south shore of Georgian Bay. From a foot-training perspective, the beach offers two distinct surfaces within a few metres of each other, and understanding the difference is half the practice.

Wet, firm sand sits in the intertidal-equivalent zone — the strip that was underwater an hour ago, or where wave wash keeps the surface saturated. It compresses only a few millimetres under each footstrike. Mechanically, it behaves like a slightly forgiving trail. Good for long sessions, good for the first weeks of training, easy on the calves.

Dry, deep sand sits higher up the beach, away from the waterline. Each footstrike sinks two to five centimetres. Pulling the foot back out loads the hip flexors and tibialis anterior hard. The arch must work much more to stabilise on a surface that gives way. This is where the strength gains come from, and also where the soreness comes from. Keep dry-sand exposure short early on.

In practice, an experienced session at Wasaga looks like this: walk out on wet sand for 20 minutes, cut up to dry sand for 10 minutes, drop back down to wet sand for 20 minutes, finish. The transitions train the foot to adapt to changing surface stiffness — a skill, not just a strength.

Foot drills you can layer in

A walk is the foundation. Three drills, done barefoot before or after the walk, accelerate the adaptation considerably.

Single-leg balance on sand, eyes open, 30 to 60 seconds per side, three rounds. The shifting surface forces continuous correction by the intrinsics and peronei. Progress to eyes closed once 60 seconds feels easy.

Towel scrunches, or in this context, sand scrunches. Sit on a towel on the beach, plant the heel, and use the toes to gather sand toward you. Thirty repetitions per foot. This isolates the flexor digitorum brevis and the lumbricals — the muscles that fail first in a "weak foot."

Short-foot exercise, described by Janda and refined by McKeon's group. Stand barefoot, keep the toes long and relaxed, and actively shorten the foot by drawing the ball of the foot toward the heel without curling the toes. Hold for five seconds, release, repeat ten times per side. This is the closest thing to a direct contraction of the abductor hallucis and the medial intrinsics.

Done two or three times a week alongside the walks, these drills are what convert a pleasant beach habit into measurable foot strength.

Practical takeaways

• Cushioned shoes unload the intrinsic foot muscles; the result is a weaker, floppier foot that fatigues earlier and transmits poor force up the chain.
• Walking on sand costs roughly 1.6 to 2.5 times the metabolic energy of walking on firm ground, with most of the extra load landing on foot, calf and dorsiflexor muscles.
• Start with 20-minute sessions on wet firm sand; build to 45-to-60-minute mixed-surface sessions over six to eight weeks.
• Mix in single-leg balance, sand scrunches, and short-foot exercise two to three times per week to accelerate intrinsic-muscle adaptation.
• Treat barefoot sand walking as a multi-month prerequisite to minimal-shoe running, not a warm-up.

Extended takeaways

The foot is one of the only major load-bearing structures in the body that most adults never train directly. We train quadriceps, glutes, hamstrings and core deliberately, but the 20-odd small muscles that determine how force enters and leaves the ground are left to whatever the day happens to deliver. For someone wearing cushioned shoes on flat floors, the day delivers very little. The slow erosion of foot capacity then shows up as plantar fascia pain, posterior tibial tendinopathy, or a vague decline in balance that gets blamed on age. McKeon's foot-core framework reframes this as a trainable deficit rather than an inevitability, and the data on sand walking gives us a low-tech, high-dose way to address it.

The Wasaga beach is, from a biomechanics standpoint, a free foot gym that happens to be 14 kilometres long. The combination of wet firm sand for volume and dry deep sand for intensity creates a natural progression that no single piece of equipment can match. The metabolic data from Lejeune and from Pinnington tells us the dose is real and substantial. The intrinsic-muscle work from Kelly and Lichtwark tells us the specific tissues are being targeted. The transition-injury data from Lieberman's group and Ridge's group tells us the slow ramp matters. None of these threads is speculative; the literature is small but consistent.

The practical implication for residents of southern Georgian Bay is unusually clean. The walk you already enjoy is, with two changes — bare feet and a thoughtful progression — a structured foot-strength program. Add three short drills, give it eight weeks, and the foot you finish the summer with is measurably different from the one you started with. Tendon, bone and muscle remodel on their own timeline. The job is to provide the stimulus consistently and to stop when the tissue says stop.

Sources cited:

1. McKeon PO, Hertel J, Bramble D, Davis I. The foot core system: a new paradigm for understanding intrinsic foot muscle function. British Journal of Sports Medicine, 2015. 2. Kelly LA, Cresswell AG, Racinais S, Whiteley R, Lichtwark G. Intrinsic foot muscles have the capacity to control deformation of the longitudinal arch. Journal of the Royal Society Interface, 2014. 3. Kelly LA, Lichtwark G, Cresswell AG. Active regulation of longitudinal arch compression and recoil during walking and running. Journal of the Royal Society Interface, 2015. 4. Lejeune TM, Willems PA, Heglund NC. Mechanics and energetics of human locomotion on sand. Journal of Experimental Biology, 1998. 5. Pinnington HC, Dawson B. The energy cost of running on grass compared to soft dry beach sand. Journal of Science and Medicine in Sport, 2001. 6. Hashimoto Y, Sakuraba K, and colleagues — sand-surface training in athlete conditioning literature, multiple papers across Japanese sports-science journals. 7. Lieberman DE, Venkadesan M, Werbel WA, et al. Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature, 2010. 8. Ridge ST, Johnson AW, Mitchell UH, et al. Foot bone marrow edema after a 10-week transition to minimalist running shoes. Medicine and Science in Sports and Exercise, 2013.

Frequently asked questions

How long until I notice a difference in foot strength?

Most people report better single-leg balance and reduced arch fatigue within four to six weeks of two to three sand walks per week. Visible changes in foot shape — a wider forefoot, more splayed toes — take several months because soft tissue remodels slowly.

Is sand walking safe if I already have plantar fasciitis?

Cautiously, yes, but start on wet firm sand only, keep sessions under 20 minutes, and stop if the morning-first-step pain worsens. The McKeon foot-core framework and clinical work by Rathleff and colleagues suggest that strengthening the intrinsics is part of plantar fasciitis rehab, but the loading dose has to be controlled.

What about glass, shells, or hot sand?

Real risks. Scan the strip you're walking before you start, especially after a busy summer weekend. Mid-afternoon dry sand can exceed 50 degrees Celsius in direct sun — walk early morning or in the wet-sand strip, or wear minimalist sandals through the hottest section.

Can I just wear minimal shoes everywhere instead?

You can, eventually, but the transition is the injury window. Lieberman's group and Ridge's metatarsal-oedema data both argue for a months-long ramp. Barefoot sand walking is one of the gentler ways to build the foundation.

Does running on sand give the same benefit as walking?

It gives a higher dose, with a higher injury risk. Pinnington and Dawson's metabolic data show running on sand costs about 1.6 times more energy than running on grass, but the impact forces and the demand on the Achilles climb sharply. Walk for a season first.

References