The problem that often occurs when doing biceps curl, whether it with dumbbells or a barbell, is that we tend to compensate with our deltoids towards the end of a set. To overcome this problem there are several solutions, such as using lighter weights.
Jeff Cavaliere has another trick to share: using a wall to avoid compensation and, especially, to solicit maximum activation of the biceps. He executes this movement in three steps.
Jeff Cavaliere's wall biceps curl
1. Set your back to the wall with a dumbbell in each hand.
2. Lift a dumbbell until it touches the wall at the top of the curl.
3. Perform the movement with the other arm while keeping the first dumbbell stuck to the wall at the top of the curl.
This version of curls will allow you to activate more muscle fibers, rather than just "pumping" with classic curls. Not to mention that touching the wall is necessary to rotate your shoulder outwards. This isolation move thus becomes a compound movement, which in addition, is beneficial for the rotator cuff.