When curling dumbbells, I can curl 50s if I’m using my body’s momentum and going one arm at a time in an up and down motion, switching between arms. I’m not swinging my arms all over the place but my arm is not stiff nor is my posture.

Today I decided to go lighter on the weight due to me being curious about whether my form is correct in which I curled 25s at the same time while keeping my back as stiff as I can along with my arms.

My question is, what is the “correct way” to do curls?

I’ve watched some videos on YouTube and also asked a few bodybuilding streamers on Twitch in which I’m still a bit puzzled. With my previous form, I was going up in weight but I believe that may be because my other muscles were helping to curl the weight whereas now, my biceps are isolated when my back is stiff— what would you guys recommend I follow through with going forward? Should I stick to my new form for a while to see if I see more progress in that manner first?