Biomechanics
Anatomy and Function of the Foot and Ankle
From the FASTER syllabus: this article is taught in full in The Field-Based Biomechanics course →
In short: The foot and ankle move as a coupled system: dorsiflexion at the ankle naturally pairs with eversion and abduction, while plantarflexion pairs with inversion and adduction — so dorsiflexion and inversion, or plantarflexion and eversion, can't happen together.
If you coach movement, you don't need to memorise a textbook — but you do need a working model of how the foot and ankle are built and how they move. Here's the version that actually matters on the gym floor.
The bones
From the lower leg down into the toes:
- Tibia — the larger lower-leg bone, on the medial (inner) side.
- Fibula — the smaller lower-leg bone, on the lateral (outer) side.
- Talus — sits above the heel bone and forms the lower part of the ankle joint.
- Calcaneus — the heel bone, and the largest bone in the foot.
- Navicular — a boat-shaped bone in the midfoot.
- Cuboid — a cube-shaped bone on the lateral side of the foot.
- Cuneiforms — three wedge-shaped midfoot bones: medial, intermediate and lateral.
- Metatarsals — the five long bones numbered I to V, starting from the inner side.
- Phalanges — the toe bones. Each toe has three (proximal, middle, distal) except the big toe (hallux), which has two.
The joints
- Ankle joint (talocrural) — tibia, fibula and talus. Allows dorsiflexion and plantarflexion.
- Subtalar joint (talocalcaneal) — between talus and calcaneus. Allows inversion and eversion.
- Transverse tarsal joint (Chopart) — two joints together: talonavicular and calcaneocuboid.
- Tarsometatarsal joints (Lisfranc) — between the tarsal bones and the bases of the metatarsals.
- Intermetatarsal joints — between the bases of the metatarsals.
- Metatarsophalangeal joints — between the metatarsals and the proximal phalanges.
- Interphalangeal joints — between the phalanges. Each toe has two, except the big toe, which has one.
The movements
At the ankle (talocrural) joint:
- Dorsiflexion — lifting the foot up towards the shin.
- Plantarflexion — pointing the foot down away from the shin.
At the subtalar joint:
- Inversion — turning the sole inward.
- Eversion — turning the sole outward.
- Abduction — moving the foot away from the body's midline.
- Adduction — moving the foot towards the midline.
Why movements couple together
This is the part most trainers miss. The foot doesn't move in tidy, isolated planes — the joints are oriented so that certain movements happen together.
- Dorsiflexion, eversion and abduction go together. As the foot dorsiflexes at the ankle, it also everts and abducts at the subtalar joint. This gives you a mobile foot that accommodates uneven ground during initial contact and mid-stance.
- Plantarflexion, inversion and adduction go together. As the foot plantarflexes, it inverts and adducts. This gives you a rigid, stable lever for push-off in walking and running.
Why some movements can't combine
Evolution has limited certain combinations to protect the joint:
- Dorsiflexion and inversion can't occur together — dorsiflexion positions the talus so the ankle locks, blocking inversion.
- Plantarflexion and eversion can't occur together — plantarflexion locks the foot in a way that blocks eversion.
The reasons are structural. Joint orientation dictates which movements pair up, and the ligaments and tendons around the foot are arranged to support those specific combinations — giving stability through the gait cycle and preventing the excessive, injurious ranges the joint isn't built for.
Understand this coupling and foot assessment stops being a list of isolated tests. You start reading the foot as one system that softens to absorb and stiffens to propel.
You just read one answer. The course is all of them.
The Field-Based Biomechanics course: every answer marked by a real tutor, with free return access for life. The price is on the page, payment plans at checkout, no sales calls.
What every FASTER student gets
Built around you, not around the course
- A real person marks every answerEvery answer is read and marked by a tutor, with written feedback.
- Marked as you goEach teaching point is marked as you answer it, not at the end of the module.
- Dictate instead of typeA microphone on every written answer: say your answer and it types it for you (Chrome, Edge and Safari).
- Listen to the lessonsVoice-overs on the lessons, and the audio to download.
- Built for the way your brain worksShort lessons, one point at a time, marked as you go, with the choice to listen, read, print or speak your answers.
- Streaks that never punish youYou set how many days a week you want to study. Miss a day and your streak pauses; it is never lost.
- Accessible to WCAG AA, with an AAA optionEvery page measured against the WCAG accessibility standard: no faults at level A or AA, with a skip link, screen-reader labels and pages that hold together zoomed to 400%. A high-contrast option takes it to AAA.
- Keep it plainOne switch turns off the extras, the streaks, the badges, the celebrations and the movement, so the site stays plain and calm. Switch them back on whenever you like.
- Bigger text and wider spacingTwo steps of bigger text, and more room between lines, words and letters, on every page.
- Calmer motionOne switch stops animations and videos that play on their own. It is on already if your phone or computer asks for reduced motion.
- A personal video lessonWhen an answer needs real explaining, your marker records a video that lands in your course.
- A note before you sendBefore you send, the page tells you if your answer copies the lesson word for word, so you can put it in your own words.
- The skeleton and muscle labsTap any bone on the skeleton, and see the muscles light up on the model.
- Print the notesPrint the lessons and go old school.
- Case studies on your phoneBuilt into the site, saved as you go, there on your laptop when you sit down.
- Pin it to your home screenNo App Store and no Google Play. It is just there.
- No resit feesWork sent back is a chance to add more, with no resit fee.
- Return access for lifeQualify once and come back to the content whenever you need it.
- PT Manager from day onePT Manager is yours to learn on from the day you sign up. Using it with real clients comes once you hold your Level 3 and are listed on the FASTER Trainer Register.
- The FASTER Trainer RegisterA free listing on the Register once you qualify.
- Your certificates in one placeEvery course and its certificate on one page.
- Ask JohnThe Ask John button on every page, and his WhatsApp.
And PT Manager, free
51 tools to run your business, with no monthly fee and no cut of your money
PT Manager is yours to learn on from the day you sign up. Using it with real clients comes once you hold your Level 3 and are listed on the FASTER Trainer Register.
See all 51 tools
Set-up
- Import clients Bring a whole client list across in one go.
- My quotes Daily lines your clients see — yours, not stock.
- Programme templates The programme shapes you reuse — a session or twelve weeks. Pick one for a client, get your own copy.
- Exercise library Every exercise with FASTER coaching detail.
- Money Products, payments and who owes what.
- Send from your own email Connect your own email service so invites arrive from you, on your domain.
- My brand & client view What your clients see when they walk in — views, header, accent, logo.
- Your enrolment pack What every new client gets the moment you enrol them — your forms, ours, or a mix.
- Products and services What you sell — blocks, packages, memberships and one-offs, with their prices.
- Insurance Your policy on record — provider and expiry. Client features unlock while it is valid.
- My menu Switch any tool on or off — for your menu, your home and your whole account.
- Your website A free website on your own web address, filled from PT Manager. Or just the client sign-in door on your domain.
- Your public page Your verified Trainer Register listing, linking out to your own site and socials.
Business day to day
- Clients Your client list — invite, open a client, manage their space.
- Clubs Group your clients — a board they share, a programme or a monthly price if you want one.
- Challenges A dated push everyone logs against — for everyone you train, or for one club.
- Calendar Sessions, classes, capacity and bookings.
- Reminders The dates your business can't let lapse — insurance and first aid, nagged ahead of time.
- Nudges Who needs a nudge today — opportunities, one tap each.
- Who needs chasing Every conversation about money, in the order to work through them.
- What needs doing Your own list, in your own words — the jobs you keep meaning to get to.
- Till Sell at the desk — cash, card or on their phone — and download the sales sheet.
- What you are making What is coming in every month, what was paid in the last 30 days, and what sells.
Templates and systems
- Forms & interviews PAR-Q, consent, consultations and your own forms.
- Coaching room The coaching tools shelf — wheels, journeys and resources in one place.
- Radar wheels Build a life or performance wheel a client fills in — see change over time.
- Nutrition by FASTER Nutrition sheets and habits without meal-plan pretence.
- Pathways Automated coaching journeys you assign to clients.
- Programmes Start a programme — a session, a month, 12 weeks or a season — and find the ones you have built.
- Games & drills planner Build game-based sessions and drills.
- Sport screens Pick a sport — the shots to film, the analyser, and a ready-made radar of the qualities that matter.
- Movement screen → radar Read joint angles off the analyser — they auto-score and fill a radar wheel.
- Assessment builder Build and run client assessments and re-tests.
- Tag analytics Every tag across your clips, grouped and exportable.
Client
- AI prompts Your reusable prompt library for coaching copy.
- Before & after Side-by-side progress comparisons.
Trainer tools
- Exercise generator Fresh exercise ideas from constraints you set.
- FASTER dice & wheel Spin-and-roll session variety for groups and games.
- Movement demonstrator A 3D model of the FASTER movement patterns — body or skeleton view, prime movers lit up, live joint angles.
- Client video analysis Your media library — client folders and your own. Pick a clip to analyse.
- Movement by FASTER (HMAC) Human movement analysis charts — see how a client moves.
- Live analysis Mount your phone and coach live — skeleton, reps, angles and depth in real time.
- Tell a group One thing, to the right people — and you see exactly who it reaches first.
Media centre
- Video builder Reels, stories and client report videos, in your own branding.
- Image builder Branded posts and cards for your socials, at the right size.
- Shot list builder Every shot with its size, angle, lens, location, people, kit and sound; sorted into shooting order, ticked off on the day, printed or sent as a sheet.
- Storyboard builder Plan a video shot by shot: what the camera sees, what is said, the move and the cut.
- Script writer Write what you will say, with the word count and how long it takes to say.
- Teleprompter Read your script off the screen at your speed, and film yourself behind it.
- Video and image organiser Everything you have made and every source you can pull from.
- Ad builder Make your own ads, coached as you go, in your branding. As many as you like, no fee, no cap.
Frequently asked
How many bones are in the foot and ankle?
Up from the leg you have the tibia and fibula, then the talus and calcaneus, the navicular, cuboid and three cuneiforms, five metatarsals, and the phalanges of the toes.
What movements happen at the ankle (talocrural) joint?
Dorsiflexion, lifting the foot up towards the shin, and plantarflexion, pointing it down away from the shin.
What movements happen at the subtalar joint?
Inversion, eversion, and contributions to abduction and adduction of the foot.
Why do some foot movements couple together?
Joint orientation plus ligament and tendon tension mean dorsiflexion couples with eversion and abduction, and plantarflexion with inversion and adduction — a mobile foot at heel strike, a rigid one at push-off.
Which movements can't happen at the same time?
Dorsiflexion and inversion can't combine, and neither can plantarflexion and eversion — the talus locks the ankle in each case to protect it.
Reading this for your own training? Every trainer on the FASTER register has been assessed by us — search by town or speciality, free.
Find a FASTER trainer →
