Neutral grip, dead pause, thick forearms and biceps.
Thumbs stay up the whole rep, don't let the dumbbells rotate.
The neutral grip lines the biceps up with the brachialis and the forearms, so every curl builds thickness through the whole lower arm, not just the biceps peak. Pausing for a full second at the top removes the bounce and turnaround momentum that lets heavier weights lie about your strength. It is the arm-day pick for lifters chasing dense, wide arms rather than just a bigger curl number.
Palms facing in shifts more work to the brachialis and forearm muscles alongside the biceps, which builds arm thickness and grip rather than just the front-on peak. It is also the stronger, more joint-friendly wrist position for most people.
The pause deletes momentum at the exact point where reps are easiest to cheat. A full second held at the top forces the muscles to own the position, so lighter dumbbells produce harder, cleaner work.
Together, as written. Curling both dumbbells at once keeps the set honest and dense, with no resting arm and no torso rocking side to side between reps.
