Your body has approximately 640 muscles, depending on who's counting. But just as your grade-school teacher gave special attention to the class "pets," you have an oversized affection for your biceps. They're relatively small as muscles go, and if your arm workouts don't rely much on biceps curls, they probably aren't growing much bigger.

But muscle-heads like me have never stopped doing curls. I may not put many in the workouts at my site, StreamFit.com (we emphasize short, efficient routines for fat loss), but I've been known to throw some in at the end of my own training sessions. I truly believe that your biceps can't reach their full potential if you don't work them directly from time to time. Whether you agree or not, I'll bet you do some biceps work anyway, just to be on the safe side.

When you do, there's no reason to settle for garden-variety curls, not when your body has dozens of muscles willing to jump in and share the love. That's why I've provided five ways to upgrade one of the best arm exercises on the planet. They'll work your favorite bundles of contractile tissue while burning fat, training your core, improving your athletic power, and making you look like someone who probably was the teacher's favorite, even if you would never admit that to your classmates. (And if you're most interested in having that abs that show, check out The Spartacus Workout Evolution, the most popular fat-blasting workout in Men's Health history.)

1. Push-up Position Hammer Curl
If you've done rows from a push-up position, this exercise will seem familiar. But by doing a curl instead of a row, you move the load farther from your center of gravity and base of support. Your core muscles, in turn, need to work harder to stabilize your spine, making this one of the best ab exercises you've probably never done.

How to do it: Grab a pair of dumbbells and assume a push-up position with your palms facing each other. Without moving your upper arm, curl the weight in your right hand toward your right shoulder. Lower it, and repeat with your left arm. Continue alternating right and left curls for 30 to 60 seconds. Add weight in subsequent workouts, but don't try to speed up the movement.

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2. Kneeling Single-Arm Curl
Your biceps have two functions: to bend your elbows and supinate your forearms. Doing both with heavy weights and low reps leads to fast results. When you do these curls from a kneeling position, with the weight on one side, your obliques work overtime to keep you upright, giving you another way to target your core and biceps simultaneously.

How to do it: Select a dumbbell you can curl for no more than 5 reps or 15 seconds. Hold it in your nondominant hand, palm in, and kneel. Keeping your elbow against your ribs, curl the weight, twisting your palm so it faces your shoulder at the top of the move. Do 3 reps a side as many times as you can in 5 minutes. Once you can go back and forth 10 times (30 total reps on each side), increase the weight.

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3. Split-jack Curl
With lighter weights, this exercise can make a good cardio drill that works your biceps. With heavier weights, it's a killer power-training exercise. The deeper you sink into a lunge and the faster you jump out of it, the more you target your fast-twitch muscle fibers. They're the biggest and strongest, and they have the greatest potential for growth. (To reach your greatest growth potential, read The Testosterone Transformation, which shows you how to boost testosterone naturally to build muscle, blast fat, and improve your sex life.)

How to do it: Hold a pair of dumbbells at your sides, palms in, feet hip-width apart. Jump into a split stance -- left leg forward -- while curling the weights to your shoulders. Return to the starting position and repeat, landing with your right leg forward. Continue for 20 seconds or 10 reps. To make it harder, drop into a lunge as you land. For a fast, 4-minute cardio workout, rest 10 seconds after each set and do 8 sets.

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4. Resistance Band Jumping-jack Hammer Curl
This not only a fun way to work your biceps, it'll send your heart rate soaring. That's because jumping out against a band (see the video or the description) targets the hip muscles that provide stability during lunges and squats but that are rarely worked directly. Strengthening these muscles can improve the appearance of your lower body while also protecting your knees. Oh, and your biceps will get some work as well. No energy to workout? Discover Why You're Tired All the Time.)

How to do it: Stand with your feet together and centered on a looped resistance band, holding the top of the band with your palms facing each other. Curl the band toward your shoulders and jump out with both feet. Reverse the move to return to the starting position. Repeat for 20 seconds or 10 total reps. Do 8 sets, resting for 10 seconds between them. You can mix it up by alternating sets of curls and overhead presses (4 sets of each).

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5. Squat Concentration Curl
Sitting at a desk most of the day closes your hips, which can strain muscles in your thighs and lower back. This move forces your thighs out and opens up your hips. Pressing your upper arms against your thighs keeps the movement at your elbows, preventing other muscles from assisting. So you get a great arm workout, while you undo some of the daily damage that your desk job causes. (Find out Why Sitting Could Be the Most Dangerous Thing You Do All Day.)

How to do it: Hold a pair of light dumbbells (10 to 15 pounds) and stand with your feet about shoulder-width apart and your toes pointed out slightly. Push your hips back and squat until your thighs are parallel to the floor. Keeping your weight on your heels, your elbows pressed against your inner thighs, and your palms facing each other, curl and lower the weights for 30 to 60 seconds. Do it one arm at a time to add an element of instability and increase the challenge to your core.

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