Bicep curl form check: a live coach on your phone
The bicep curl looks like the easiest lift in the gym and is the one most often cheated: the back rocks, the elbows drift forward and the weight is swung up instead of curled. A good curl keeps the upper arm still, curls until the forearm is close to vertical and lowers to straight arms under control.
No equipment needed. Practise at home. Just do the rep properly in front of your phone. Bodyweight squats, push-ups and lunges need nothing at all, and you can check the hinge and press patterns with a very light weight or none: the coach judges your movement, not your kit.
What good looks like
- Stand tall with your elbows against your sides and the weights hanging at straight arms.
- Curl by bending only at the elbow, keeping your upper arms still and your elbows by your ribs.
- Squeeze at the top, with your forearms close to vertical, without leaning back.
- Lower for about two seconds until your arms are almost straight, then repeat without a bounce.
Common mistakes and how to fix them
Swinging the weight up
Rocking your back or hips to lift the weight takes the work off the biceps. Use a lighter weight and keep your torso still.
Elbows drifting forward
When the elbows travel forward the shoulders do part of the lift. Pin your elbows to your sides.
Cutting the bottom short
If your arms never straighten the biceps never get their full range. Lower until your arms are almost straight.
What Formanti checks on your bicep curl
The top of every rep, judged the same way. Plus a check that your torso stays still between the two.
- Elbows: 145–186°. lower to almost straight arms
- Back angle: -5–15°. stand tall at the bottom too
Your curled
The low point of every rep, judged against the guide ranges.
- Elbows: 50–100°. curl until your forearm is close to vertical and your biceps are squeezed
- Elbow position: 0–45°. elbows stay by your sides
- Back angle: -8–16°. stand tall: no swinging the weight up
What you hear and see when you are off
Curl all the way up
The coach says: “Curl all the way up”
On screen: Curl all the way up.
Drill: Pause curls: hold the top for 1 second, squeezing, then lower for 2 seconds. Use a lighter weight if you can't reach the top.
Keep your elbows by your sides
The coach says: “Elbows in”
On screen: Keep your elbows by your sides.
Drill: Curl with your back against a wall and your elbows touching your sides, so they can't travel forward.
Don't lean back to lift it
The coach says: “Don't lean back”
On screen: Don't lean back to lift it.
Drill: Curl with your back and heels against a wall so you can't swing.
Stand tall, don't fold forward
The coach says: “Stand tall”
On screen: Stand tall, don't fold forward.
Drill: Curl with your back against a wall.
Lower all the way down
The coach says: “Full stretch”
On screen: Lower all the way down.
Drill: Curl with a 1 second pause at the bottom, arms long, then lift.
Don't lean back at the bottom
The coach says: “Don't lean back”
On screen: Don't lean back at the bottom.
Drill: Curl with your back against a wall.
Stand tall at the bottom
The coach says: “Stand tall”
On screen: Stand tall at the bottom.
Drill: Curl with your back against a wall.
Stop swinging the weight
The coach says: “No swinging”
On screen: Stop swinging the weight.
Drill: Strict curls with your back against a wall, 2 seconds up and 2 seconds down.
Drills you can do alone
- Wall curls: stand with your back, hips and heels against a wall and curl without letting your back leave it.
- Tempo curls: two seconds up, a one-second squeeze, two seconds down, with a lighter weight than you think you need.
How to set up your phone
Phone at chest height, 2 to 3 metres to your side, whole body in view. Both arms together, or one arm at a time with the working arm nearest the camera. Dumbbells, a bar or a band. Film from the side: back and hip angles cannot be judged head-on. It all runs on your phone and nothing is uploaded.
Ranges set from real phone video of 13 people curling with good form (a public dataset), side-on. Tested on 26 people (13 held back from setting the ranges): it flagged about 5% of good reps and caught 12-36% of badly-formed ones, mostly swinging and rocking. Not reviewed by a coach. For alternating curls it counts the arm nearest the camera.
Frequently asked questions
Can a phone check my bicep curl form?
It can count your reps and measure how far you curl, how far your elbows drift and whether your torso swings. It cannot see the weight, your grip or your wrists, so treat it as a guide.
From which side should I film a curl?
Either works for counting and for the curl itself. From the side the phone can also see your torso rocking and your elbows drifting forward.
More lifts to check
Deadlift · Squat · Push-up · Lunge · Overhead press · Bent-over row · Romanian deadlift · Tricep extension · Lateral raise · Glute bridge · Pull-up · Dip · Sit-up · Jumping jack · Plank · Wall sit