Become a Personal Trainer
What Muscles Work In A Lunge, And How To Work It Out For Any Exercise
From the FASTER syllabus: this article is taught in full in The honest route from scratch to qualified →
In short: A lunge works the quadriceps at the front knee, with the gluteus maximus and hamstrings at the front hip, the same prime movers a squat uses. The adductors and the trailing leg's hip flexors assist, and the gluteus medius works harder here than in a squat, because a lunge only has one foot on the ground at a time to keep the pelvis level. The four steps that produce that answer are: decide where the force is acting, find the muscles working directly against it, find the muscles assisting, then find the muscles supporting the joint — the same four steps that answered the same question about a squat.
What muscles work in a lunge
The quadriceps at the front knee. The gluteus maximus and hamstrings at the front hip. The adductors assisting, the trailing leg's hip flexors and quadriceps controlling how the back knee lowers, and the gluteus medius working harder than it would in a squat, because a lunge only ever has one foot on the ground to keep the pelvis level.
That is the answer. The useful part, again, is that it came from a method rather than a memorised list, and the same method works on whatever a client is doing next.
The same four steps as the squat, because they work on anything
A recent post here ran this method on a squat. One of the things you learn on our CIMSPA-recognised personal training course is that the method does not change from exercise to exercise, only the answer does:
- Decide where the force is acting on the body
- Identify which muscles work directly against that force (muscles that lengthen are easiest to see)
- Identify which secondary muscles assist that movement
- Identify which muscles would support that joint / movement
Run it on a lunge.
One, where is the force acting? Straight down through the body, the same as a squat, but now split across a staggered stance rather than shared evenly between two feet under the hips.
Two, what works directly against it? The front leg takes most of it. Going down, the front knee bends and the front hip folds, so the quadriceps lengthen at the knee and the gluteus maximus and hamstrings lengthen at the hip, under load. Same prime movers a squat uses, doing the job through one leg instead of two.
Three, what assists? The adductors on the front leg, pulling it back toward the midline on the way up, and on the trailing leg, the hip flexors and quadriceps controlling how far and how fast that back knee drops.
Four, what supports? The erector spinae, holding the spine over a base that is now longer and narrower than a squat's. And the gluteus medius, doing more work here than anywhere in a squat, because a squat has two feet sharing the job of keeping the pelvis level and a lunge only ever has one.
Why that fourth answer is worth having
A trainer who only knows "lunges work the legs" has nothing to say when a client feels it more on the outside of one hip than the other. A trainer who has run the four steps knows that is very likely the gluteus medius, doing the extra stabilising job a lunge asks of it and a squat mostly does not, and can say so plainly instead of guessing.
Point it at anything
A step-up. A single-leg deadlift. Any exercise with one foot doing more of the work than the other asks the same fourth question, and the answer is usually the same muscle group doing a bigger job than it does standing on two feet.
What to do next
The whole route from no qualification to working trainer is set out at become a personal trainer. It sets out what Level 2 and Level 3 contain, what it costs, and how long it takes. The price is on the page, there are no sales calls, and free lifetime return access is included, so the anatomy unit is still there the week a client asks about a hip you have not thought about since the exam.
The anatomy unit itself sits in Level 3 Personal Trainer, and in the Certified PT Bundle at £1,500 alongside Level 2 and Movement Trainer.
FASTER Daily News sends you each day's blog links, the latest on new courses and live opportunities, and updates to PT Manager, free for students. Sign up at /newsletter.
You just read one answer. The course is all of them.
The honest route from scratch to qualified: 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.
Also worth a look: Level 3 Personal Trainer — the anatomy unit this comes from.
See what the course covers →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
Why does a lunge need a different muscle than a squat if the four steps are the same?
It mostly doesn't — the front leg is doing the same job a squat asks of both legs together. The difference the steps turn up is the gluteus medius, working harder to hold the pelvis level because only one foot is on the ground.
Does this method work on exercises that aren't lower body?
Yes. The same four steps answer the question for a row, a press-up or a carry — decide where the force acts, then find the muscles working against it, assisting it, and supporting the joint.
Does finishing the course get me PT Manager?
Yes. PT Manager opens the moment you sign up with FASTER, and adding real clients unlocks once you pass a course.
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 →
