Plank: proper form and the mistakes the camera catches
The plank builds core strength by holding your body in one straight line. Here is how to hold a proper plank, and how the camera tells a straight line from a sagging one.
How to do a plank
- Start in a push-up position, hands under your shoulders.
- Brace your core and squeeze your glutes so your body forms one line from head to heels.
- Keep your neck neutral and your hips level: not dropped, not raised.
- Breathe normally and hold, then lower down with control.
Engine thresholds · plank
How the camera judges your plank
For a hold there are no reps: the engine measures how straight your body line stays from shoulders to ankles, and times only the seconds you hold good form.
Target hold
30 s
Body line: warning at
5° off
Body line: error at
9° off
Errors checked
3
What the camera catches
Common plank mistakes
Hips dropping
The hips sag toward the floor and load the lower back.
Trigger back angle < 145°
Fix: squeeze your glutes and pull your belly button in.
Body out of line
Shoulders, hips and ankles drift out of one straight line.
Trigger body line more than 9° off straight
Fix: reset to a straight line from head to heels.
Shaking core
The torso shifts or wobbles during the hold.
Trigger back angle swings > 8°
Fix: shorten the hold and keep every second clean.
These are the thresholds the app uses for the plank (its own rule set plus the general checks in the pose engine), exported from the app's code for this page.
Plank questions
How long should I hold a plank?
Start with 20–30 seconds of good form and add time as it stays straight. Several short clean holds beat one long sagging one.
Should I plank on my hands or elbows?
Both work. Elbows are easier on the wrists; hands are closer to a push-up.
Why does my lower back hurt in a plank?
Usually the hips are dropping. Squeeze your glutes and shorten the hold until you can keep the line.