The BicepsBiceps, believe it or not, are a relatively small muscle group, and while a lot of upper body exercises hit the biceps, you wont tap in to their full potential without targeting them directly. Building big, shaped biceps will take more than your standard dumbbell curls. To see a real increase in size, you need to attack both heads of the biceps from every angle. Having a wide range of curls in your repertoire and rotating through them often, while constantly changing rep speed, number and resistance, are all key.Theres no need to work your biceps more than a few sets. They receive so much indirect tension from other upper body exercises, 3 sets of 2-3 exercises will do the trick. Try these 4 bicep curl variations to take your guns to the next level.Isometric CurlsThe more time under tension, the more your biceps will grow. Alternating isometric holds with reps means there is no rest, despite reaping the benefits of working each bicep independently. Try it:Stand with your feet shoulder-width apart, your arms extended by your sides, a dumbbell in each hand. Keeping your elbows tucked by your sides, flex both elbows to 90 degrees. This is your starting position.To begin: extend through the left elbow, lowering the dumbbell to your thigh while holding the 90 degree angle in your right elbow. Then flex through the left elbow to curl the dumbbell to your shoulder.Extend through the left elbow, lowering the dumbbell back to 90 degrees and stop. You should be back to starting position.Holding the 90 degree angle in your left arm, repeat on your right side: Extend completely through the right elbow, then curl the dumbbell to your shoulder, then extend, lowering the dumbbell to 90 degrees, back at starting position. Continue, alternating curls with isometric holds. Cable Preacher CurlsUsing the cable machine while performing isolation preacher curls provides consistent resistance in both directions. Because the preacher bench holds your elbow stationary, you have more leverage, so you may find you are able to lift more weight than youre used to. Try it:Place a preacher bench a few feet in front of a pulley machine. You can use an incline bench if you dont have one; youll just need to stand.Use a short, straight bar and attach it to a low pulley.Sit at the preacher bench, or position yourself behind the incline bench with the backs of both arms, your triceps, placed firmly on top of the pad.Grab the bar with an under hand grip and fully extend your arms. This is your starting position.To begin: Flex the elbows to slowly curl the bar toward your shoulders. Squeeze your biceps hard at the top of the contraction and hold a moment. Extend through the elbows to return the bar to your starting position and repeat.Prone Incline Bench CurlsLying across the bench gives you nothing to brace your arm against. It isolates the biceps, while eliminating the peck and shoulder muscles from the movement--something thats tough to do when youre standing upright.Try it:Grab a dumbbell on each hand and lie prone with your chest pressed against the back of an incline bench set at an 85 degree angle. You can kneel on the seat or straddle your legs over the seat, whichever feels most stable.Extend your arms and let them hang. They will be perpendicular to the floor.Keeping your elbows stationary, rotate your wrists so your palms are facing forward. This is your starting position.To begin: Flex through the elbows, contracting only the biceps to curl the dumbbells to your shoulders. Squeeze your biceps hard at the top of the contraction and hold a moment. Slowly extend your elbows to lower the dumbbells back to your starting position and repeat.Negative CurlsNegative curls load the bicep during the eccentric phase, or during the downward movement of the weight. You can use negative training for any exercise, but it is always best done with a partner to help you during the concentric portion. Negative training allows you to lift beyond failure, sometimes up to 40% more weight than usual, stimulating even more growth. Try it:Do your normal barbell or dumbbell bicep curls, but grab a partner and about 30% more weight. Start with the weight at your chest. To begin the rep, lower the barbell as slowly as you can, fighting for every second. Once your arms are fully extended, use the help of your partner to curl the weight back to your chest to repeat.   To maximize your results and view optimal form, check out our colleciton of bicep moves on Shredz FitClub.