The standard biceps curl is hardest at the mid-range, where the lever arm is the longest. But for variety we can change that, making the top or peak contraction the toughest part of the movement.
Lean forward at a 45-degree angle.
Don't drop the elbows down. Keep the upper arm in line with the body.
Perform curls in this position, squeezing hard at the top.
A rep is not a rep. Especially when you stretch it out 30 times longer than how it's normally done. Sounds crazy, but so are the gains you'll get from it. Check it out.