KAMALU CURLS | The #1 Best Science-Based Biceps Exercise You'll Ever Do (Plus 90° Rule Explained)

The Komalu Curl is done by starting with your hand gripping the end of a cable, or a single-sided rope, or wedge, or any instrument that allows you to position your hand in a hammer grip like you see, and then facing away from the cable with your arm extended behind your back at the shoulder. As I'll show you here in a minute, this puts your biceps in a maximally extended position. Then, as you start to curl your arm up, you'll slowly rotate your body until you're facing the cable for the second half of the curl, and then finish by squeezing the end of your forearm as close to your shoulder as you can get it with your elbow elevated. And again, as I'll show you here in a minute, that puts you in the position of maximal contraction of the bicep muscles. Now, why is this the single best exercise for your biceps? Well, first, let's get into the anatomy. The biceps has two origination points, but neither are where you would expect them to be. When you think of the biceps, you think of flexing the elbow, so it would make sense if the biceps originated on the humerus and inserted down on the radius, and therefore, when contracted, would bend the elbow. However, both of the origination points are actually up on the shoulder. The short head originates from a part of the scapula called the coracoid process, and the long head originates from another part of the scapula called the supraglenoid tubercle. And then they both travel down to insert on your radius. So, since they pass over both joints when they contract, not only do they flex the elbow, but they also flex the shoulder. There's another reason why it's really important to understand the origination and insertion points of muscles. In weightlifting, you want to be able to work a muscle at its full range of motion. So you want to be able to hit it at maximum extension, as well as maximum contraction, and everywhere in between. That's important both for optimizing muscle growth and for preventing injury. However, it's normally very difficult to go all the way from maximal extension to maximal contraction while maintaining consistent resistance. In fact, it's impossible to do unless you have a way to alter the angle of resistance. This can be a little complex to understand, but bear with me here, I promise it will make sense. In order to get maximum extension of any muscle, and extension is just another way of saying stretch, so maximum stretch in the muscle, you have to get the origination point as far away from the insertion point as possible. So if you think about it, you have a muscle that's connecting two points. Well, if you can pull those points further away from each other, that's going to extend the muscle. So in the case of the biceps, since both of the origination points are on the front of the shoulder, and the insertion point is on the radius, so right on your forearm, then in order to get those as far away from each other as possible, one, your elbow has to be extended, and two, you actually need to have your arm extended behind your back at the shoulder. So how does the Kamalu Curl start? With the elbow extended and the arm extended behind the back. Now, in order to get maximum contraction of a muscle, you do the opposite. You want to get the insertion point as close to the origination point as possible. So, in the instance of the biceps, you want to get an insertion point on the forearm as close to the origination points on the shoulder as possible. And so, in order to do that, you have to bring the elbow up, and then you also need to elevate the elbow to get that point as close as possible to the shoulder. And guess what? That's how the Kamalu Curl ends, in maximum contraction of the bicep. However, if all you had to do to work the full range of motion of a muscle efficiently was go from max extension to max contraction, then, well, that's easy then. Grab a dumbbell, start here, and end here, right? What's with the rotation and everything? Is that just for style points? Well, this is where the 90-degree principle comes in, and it's very important to understand, not only for this exercise, but for every exercise that you do in weightlifting. Maximum resistance in any weightlifting move comes when you are working at 90 degrees to the source of resistance. To put that into practical terms, let's say you have a free weight like a dumbbell. Well, with free weights, the resistance is always gravity, which always goes straight down. Gravity is pulling everything down to the earth. So, if I were to curl using a dumbbell, then maximum resistance would happen right here, when I have a 90-degree angle to the resistance. When the curl starts down here, there's very little resistance, because the motion from here to here is not 90 degrees to the resistance. It's almost parallel to it. But, as I go up, then slowly that approaches closer and closer to 90 degrees, right here is when the maximum amount of resistance is on that muscle. Then, as I continue up, resistance slowly declines again, until, when it's straight up and down again, there's virtually no resistance going from here to here, because I'm not moving at 90 degrees to resistance. It's close to zero degrees. Try this out, and you'll see what I mean. If you were to grab a weight and try to hold it right here, you could hold that thing all day. Or, hold it right here, with only a little flex, again, you'll hold that all day. But, you put that at 90 degrees, and completely different story. So, let's see how I incorporated this principle with the Komalu Curl. When the motion starts, we're very close to that 90 degrees. When you're using a cable machine, then it's a little different from free weights, because, all of a sudden, you can change the angle of resistance. It's not always going to be straight down. It's whatever the angle of the actual cable is. So, when the motion starts, we're at pretty close to 90 degrees. We're getting up to it, we hit it, and then we start to go past it. But, by the time we are passing 90 degrees, you're rotating your body. Now, what would happen if we didn't rotate our body? Well, we'd reach that 90 degrees, and then we would continue up, and we would be losing resistance that entire time, until, by the point you get to the top of the curl, there's very little resistance from that cable. Because you're moving now parallel to it, and, therefore, having very little resistance to that motion. So, if you were to stay in one place and use that cable, you would have the same limitations as you do with gravity. You're only going to get maximum resistance at one point in that motion. So, by rotating your body, you're able to alterate that. By the time I start to pass 90 degrees, I rotate my body, and, all of a sudden, look what happened with that angle again. Now, it's once again back to 90 degrees from the cable. And that means, on the second half, I still am getting a lot of resistance. It's not going to be perfectly 90 degrees throughout the whole time, but, by rotating your body, by altering the angle of resistance in relation to the angle that you are pushing or pulling, you're able to maximize the amount of resistance that is happening on your muscle throughout the entire motion. Now, if you're still not convinced, here's another reason why the Komaru Curl is so effective. The biceps actually have another role that we haven't discussed. They do more than just flexing the elbow and flexing the shoulder. You can see that by taking a closer look at the insertion point of the biceps. We discussed how it goes down and inserts on the radius, but, if we pay a little closer attention to that, we'll see that it actually inserts on a specific knob called the radial tuberosity, and that radial tuberosity is located on the medial side of the forearm, the medial side of the radius. So, it's not pulling from directly above it. If it were, then all it would do is flex the arm. But, since it's pulling from the medial side of the arm, it's going to rotate that arm inwards as it contracts. This is what's called supination. Again, try this out yourself. Put your arm at a 90 degree angle, and then grab your bicep with your other arm, and supinate your arm. Just go back and forth, rotating your arm and your palm up, and you'll be able to feel every time you supinate your arm, your bicep contracts. So, you can actually work your biceps very well without even flexing the arm. You could keep it at the same angle, and just put resistance onto that supination movement, and I actually do that in some of my workouts. So, how did I apply this principle in the Kamalo Curl? Well, now that we know a little more detail about the insertion point of the biceps, we know that in order to get maximum extension, not only do we need to do the opposite of flexion by extending the elbow, but we also need to do the opposite of supination, and that's pronation. So, pronating the arm down gets that insertion point even further away from the origination point, making sure that we are getting maximum extension of the biceps at the beginning of that motion. And so, that is why you start this motion in a hammer grip. For those who don't know, a hammer grip is a type of bicep curl where you start with the palm pointing to the side, rather than up, in a classical curl. So, make sure you're not starting this motion with an open palm. Make sure that you really do have it in a hammer grip, with your thumb pointing up. And then, while you're flexing and rotating, the other thing that rotating really forces your muscle to do is it makes you supinate your arm as you come through. And then you finish that supination in the final part of that motion. So, not only are we getting the maximum extension and contraction in flexion of the bicep and of the shoulder, but we're also getting that full supination motion throughout this exercise. If you do these right, you'll have very little juice left in you at the end of a set. But, if you do, then there's a finisher I use where I'll simply face back and then rep out as many of the first half of the motion as I can, and then rotate and assist using the other hand in order to rep out as many of the final half of the exercise as I can. Now, the reason I do this is because you actually have more power in that first half of this motion, and so you will be limited in your full reps by how many of the second half you can do. You'll be able to do a lot more of the first half. So, in adding this finisher, we've really gotten as many reps as possible that we can out of that first half of the movement while still balancing it out with some final reps of the second half. This is a concept that I call double failure, where you take two different parts of a workout where one is slightly easier than the other, and so you go on the harder one until you reach failure, and then move to the slightly easier aspect until you reach failure again. Try out the Kamalu curls next time you work your biceps, and I promise your biceps will never be the same. It can be a little difficult to get this motion down at the start, but stick with it, and pretty soon it will start to feel natural, and you will definitely notice the difference. 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