Posted by: Ron
There are many ways to perform the curl, if you want to maximize its benefit for your biceps, do it this way
Perform your dumbbell curls with your thumbs under the handle for maximum biceps development
This curl was one of Vince Gironda's favorites. Make sure you have a mirror nearby to watch your arms and be able to concentrate fully. It will allow you to adjust your form if you tend to fall into old patterns.
Fold your thumbs under the handle and keep them there throughout the whole set. Keep your upper arms firmly pressed to your sides, elbows "stuck" to your sides. Fully extend your arm by actually flexing your triceps at the bottom of the curl. This ensures you get full range of motion and you work the lower part of your biceps to the maximum possible.
At the top of the curl, your elbows must still be stuck to your sides so you'll notice the dumbbell will be quite far away from your shoulder, yet the biceps will be contracted. Hold that position for a second or two, squeezing your biceps and imagining them as you want them to be.
This is the last part, throughout the whole curl, keep the palm of your hand level with the ground.
If you have trouble feeling your biceps thoroughly and your forearms take over, this technique will build that brain-muscle pathway and allow you to feel your biceps more. This specific way allows you to use the most affective movement for your biceps otherwise you're training the wrong muscles. I'm sure you've seen guys in the gym with oddly shaped biceps and forearms.
Do this exercise twice a week with at least 72 hours between your workouts and let me know how it worked for you.