Curling is dear to a bro's heart. The feeling of blood gushing into your upper arm with veins popping all over while listening to your favorite workout song is addictive. Some bros have something to show for it as they pack massive weaponry dangling next to their torsos. Some bros have nothing to show for it as their upper arms resemble a weirdly colored spaghetti. On paper performing a curl looks like the simplest thing in the world: you hold something in your hand and flex your arm. Easy! Then why is it pretty rare to see an impressive set of biceps at the gym? Everybody and their mother is curling everyday like it's Saturday pre-clubbing, yet the only thing impressive about most bros is their enormous library of incredibly lame pick-up lines. What's going on here?
All of the following terms will be used extensively in the upcoming sections of this write-up. Come back here if you get confused. Everybody who's training with a barbell on a regular basis should know this:
The elbow is a hinge joint. It is designed to be flexed by the biceps and smaller forearm muscles and to be extended by the triceps. If movement is restricted at the wrist (which is a pivot joint and can move in numerous planes), torque will be transferred to the elbow which often causes tendon inflammation since the elbow joint is only supposed to hinge.
The biceps has 2 heads, a long head and a short head. Both heads originate at the shoulder blade and attach at the radius, one of the two forearm bones, the other one being the ulna.
The biceps has 3 functions:
Supination of the wrist (= palms facing forward), elbow flexion (= hinge) and shoulder flexion (= raising the arm).
At first, this looks like the best exercise to do if you want to train your biceps. It trains 2 functions of the biceps: supination and elbow flexion. This must be better than doing curls where your palms face forward (= no supination) right? The biggest downfall of the Alternating DB Curl is that you're only generating maximal tension through the mid-range of each repetition. This allows for a lot of overload, but also introduces the possibility to turn this into a suboptimal exercise in order to get the weight to the mid-range point of overload.
Let's take a look at the following video. I'll go over the concentric portion of one repetition by looking at 6 distinct positions/frames and make notes why this is poor technique if maximum tension on the target muscle group is the goal.
The starting position places the dumbbell next to the body in a neutral (hammer) grip. Your body is not in the way of the dumbbell and you can fully extend the elbow*. Essentially this causes you to initiate the concentric portion of the rep as if it's a hammer curl, mostly targeting your brachialis and brachioradialis. This is not a huge problem as supination immediately follows, but it's worth noting.
*I will later cover how you can work around this even when you're using straight bars.
With heavier dumbbells the start of each rep is often accompanied by a slight forward lean to get some momentum going. I'm not pointing this out because I want to be as annoying and picky as possible about one's curl technique, but because it has consequences for how the rest of the rep looks. Keep the elbow position shown here in mind.
Once the dumbbell is in front of the torso, the lifter initates supination of the wrist. Notice the angle between upper arm and forearm. The elbow is coming forward a bit more, telling us that shoulder flexion is taking place along elbow flexion. This is important for the next 2 frames.
The wrist is now fully supinated. The elbow has traveled even more forward and is now in line with the midline of the body. We can see that the upper arm/forearm angle is relatively the same when compared to the previous frame. This means very little elbow flexion is responsible for the weight being moved to this position. This and the upcoming frame are key to all of this.
The elbow is a hinge joint, hence curling equals hinging. The hardest part of a standing dumbbell or barbell curl is when your forearm is parallel to the ground since the lever arm is longest at that position and the most amount of force is required to overcome gravity. Simply think about the distance between your elbow and the dumbbell. The shorter that distance, the easier that portion of the repetition. Once you add shoulder flexion (raising the upper arm), another variable is added to the equation and additional muscle groups are targeted. Adding shoulder flexion causes your front deltoid to take some of the load and reduces the stress on your biceps. Notice how the upper arm/forearm angle only decreases slightly between frame 03, frame 04 and this frame.
The repetition finally gets finished by fully flexing the elbow. The elbow is way in front of the torso and the weight almost "sits" on top of the elbow joint, making the last portion of the rep very easy. This does very little for biceps development and is simply done for peace of mind to "finish" the rep.
I did not create these frames to overanalyze a simple movement like curling a dumbbell. The graphics including the angles pictured above are simply there to illustrate that a lot of lifters do more of a front raise than a curl. Obviously the angles are not 100% accurate, but they visually support my argument. If you complain about the lines not being drawn with impeccable anatomical precision, you need a girlfriend.
Don't get me wrong. The Dumbbell Curl is a solid exercise, but you just learned about a lot of possible ways how this exercise can take a turn for worse, especially once you get up to heavier weight and how that changes the stimulus on your biceps. In order to change the resistance curve in our favour, the path the dumbbell travels has to be slightly altered.
The Modified DB Curl starts with your elbow extended and your shoulder slightly flexed. This allows you to use a supinated grip right from the start of each repetition and puts tension on your biceps in the bottom position. As you initiate elbow flexion, move your elbows back like you're performing a rowing motion. This will put your shoulder in extension, making it impossible to help lift the weight with your front deltoid. Finish the rep by bringing the dumbbell all the way up to your armpit while extending your shoulders. At no point throughout the exercise should you feel like there is little or no tension on the biceps, like say in the bottom or top third of a regular dumbbell curl.
Another fine way to curl unilaterally is to use cables. They naturally pull your shoulder into extension and by that solve a plethora of potential problems right from the get-go. You can make the bottom portion of the movement harder by stepping further away from the cable stack. Hence standing closer to the cable stack makes the top portion of the movement harder. I wouldn't put too much thought into the ideal distance from the cable stack. Just make sure your elbows stay behind your body in one place.
With straight bars you want to flex your triceps while the bar is touching your quads. This eliminates the possible disadvantage of your body being in the way of the bar. From there drag up the bar along your body until you reach the nipple line. The bar does not necessarily have to touch your body, but keep it as close as possible to ensure shoulder extension. Be honest with yourself and perform perfect reps. Try these for very high reps (25-30) and watch your lower biceps go up in flames.
Use higher reps for all suggested exercises. Go for at least 12 reps and see which rep range allows you to progress best. Depending on your training level you can train your biceps every 24-72 hours, the more advanced you are the shorter the required rest between sessions. Go for 3-5 sets every session, pushing close to failure on your last set.
For every guy who cheat curled his way to big biceps, there are 10 guys who cheat curled their way to inflamed shoulder tendons and no biceps. Do it right, regardless of your genetics. When it comes to curls you want to be a surgeon. Save the lumberjack for your heavy leg and back work.
John Meadows said it best: "Pump them full of blood, stretch them, feed them and watch them grow."
I'd add to that perfect technique and a long-term progressive overload approach. It is not possible to add weight and reps to your curls every week, let alone every workout. Focus on execution and biofeedback and move up in load once you've mastered a certain weight. Be patient and grow some pythons. Maybe your pick-up lines will improve along with your increasing arm circumference. Bro.