Dumbbell spider curls for a peak that won't quit.
Let the arms hang dead at the bottom. That full stretch is where the growth lives.
Chest down on the incline with a dumbbell hanging dead from each arm, the biceps get loaded from a full stretch and have to work independently through the whole curl, no bar to let a stronger arm carry the weaker one. The bench takes your torso out of the equation entirely, so every rep is honest contraction. It earns its place as strict arm work that exposes and fixes left-to-right imbalances a barbell hides.
Both at once is the standard and keeps the set efficient. If one arm consistently lags, switch to alternating reps for a while so you can put full focus on the weaker side.
You can. Starting neutral and supinating as you curl adds the twisting function of the biceps, which the barbell version cannot offer. Keep palms forward throughout if you want maximum simplicity.
Because your arms hang straight down, the biceps are stretched and loaded right from the dead hang. That deep stretched position is exactly what makes this variation productive, so never cut it short.
