Lunge Form Check
Is your lunge actually good? Prop your phone up and find out — GoodReps watches your knee angle (hip → knee → ankle) live and scores every rep as you train your quads and glutes, with hamstrings and calves assisting. Free, in your browser, processed entirely on your device.
▶ Check My Form FreeHOW TO DO A PROPER LUNGE
Setup Turn side-on to the camera, feet hip-width, hands at your sides or on your hips.
- Step one foot forward and lower until both knees are ~90°.
- Keep your front knee over your ankle and your torso upright.
- Push back to standing and alternate legs.
This is the same instruction sheet you’ll find on the ⓘ panel inside the app — with an animated demo next to it.
THREE STEPS TO A SCORED LUNGE
Prop your phone and get in frame
Set your phone at roughly torso height and set up side-on to the camera. The built-in camera test confirms your lighting, distance, and angle with live green checks before you start.
The AI locks a 17-point skeleton on you
GoodReps measures your knee angle (hip → knee → ankle) in real time, entirely on your device. No wearables, no sensors. Bodyweight to start; hold dumbbells when it gets easy — log them, track PRs.
Move — and watch the form bar
The bar fills as you travel from ~160° toward ~100° at the bottom. Stop short and it tells you; a rep only counts through the full range of motion.
WHAT THE CAMERA WATCHES
- Your knee angle, live — from roughly 160° standing down toward 100° in the split. Shallow dips don't bank; a real lunge does.
- Your personal range of motion — after 3 clean reps the counter calibrates its thresholds to how you move.
- Your depth on every step — come up short and the form cue nudges you: "Deeper lunge."
COMMON LUNGE MISTAKES
Steps too short
A cramped stance forces your knee past your toes and steals depth. Step long enough that both knees can reach roughly 90°.
Torso pitching forward
Leaning over your front leg turns a leg exercise into a balance rescue. Ribs stacked over hips, eyes forward.
Back knee never drops
The rep isn't the step — it's the descent. Lower the back knee toward the floor under control before driving up.
Pushing off the toes
The drive comes from the front heel. Press the floor away through it and your glutes take over from your knees.
PRIVATE BY DESIGN
Pose detection runs in your browser via TensorFlow.js. Camera frames are analyzed in real time and immediately discarded — nothing is recorded, nothing leaves your phone, and we never see them. Sign-in is optional; skip it and everything stays local.
QUESTIONS, ANSWERED
Do I need any equipment to count lunges?
No — bodyweight lunges work out of the box. Add dumbbells at your sides when you're ready and log the weight for PR tracking.
Does it work in a home gym or low light?
Run the built-in camera test first — it checks your lighting, distance, and angle with live green checks before you start. If a rep still slips through, manual counting is always one tap away.
Is my camera feed uploaded anywhere?
No. Pose detection runs entirely on your phone, in your browser. Frames are analyzed in real time and immediately discarded — nothing is recorded, nothing is uploaded.
RELATED GUIDES
Free forever — camera counting for all 60 exercises, no account needed. Pro (voice coaching, programs, depth-camera form checks) is $7/mo, $49/yr, or $99 once. No ads, ever.