Don’t bother googling. There are way too many articles out there titled something like: “5 BEST BICEPS EXERCISES” “10…” “15…” Can we get 20? Yes! No joke, that’s really a thing, in Men’s Health: “20 BEST BICEPS EXERCISES.” The difference between this article and all of those is this won’t be a random cluster of every kind of curl. Instead, we’ve got the research. Researchers have measured the activation of the biceps during the exercises on those lists, and, forget all that clickbait that failed to deliver, we’re going to tell you which one truly is the best.

CURL GEOMETRY

First, some physics and a little geometry. When doing any full-length, free-weight curl, gravity fights to pull the weight straight down to the floor, but, complicating things, your hands (and the weight) travel in an arc. Its only when your forearms are parallel to the floor on each rep that gravity exerts its maximum pull and thus your biceps toil their hardest.

Biceps Activation During Typical Free-weight Curl

Let’s take this a step further with a clock illustration. We’ll use color zones to simplify (biceps activation would actually be progressive throughout). The center is your elbow joint. The minute hand is your forearm, and it starts pointed straight down to 6:00. Your forearm goes through about a 130-degree range of motion during any full curl rep, so it finishes pointed a little past 10:00.

When doing curls with your upper arms perpendicular to the floor (such as a standard barbell curl or seated dumbbell curl), the bottom halves of reps (to 8:05) are a breeze. The tops of reps are getting easier as you reach contraction (10:10), so you’re unlikely to fail there. It’s the red zone (8:20 to 9:40), especially the parallel crimson (9:00) when you’re about 70% of the way through and gravity is pulling the hardest, where reps go to die.

STUDY TIME

The American Council of Exercise published a study in which eight young men and eight young women performed eight biceps exercises while the muscle activity of their biceps, anterior deltoids, and brachioradialis were monitored via electrodes attached to an EMG machine. Results were measured against each person’s maximum voluntary contraction (MVC) of his or her biceps. And the grades are…

concentration curl

THE CLEAR WINNER  

As its name almost demands, the concentration curl allows you to focus on one biceps from start to finish on each rep. Bracing the back of your elbow against your inner thigh prevents cheating, but this exercise’s greatest advantage is that you can easily squeeze contractions, perhaps expanding the red zone all the way to the end. An earlier EMG study also ranked the concentration curl No. 1 (and was especially positive about the negative concentration curl, focused on slowly lowering the weight). Many people think of concentration curls as a light, pumping move, easy to leave out as you pummel your bi’s with heavy EZ-bar and dumbbell curls, but this is one you shouldn’t skip.

One caveat: This test measured muscle activation. There are other considerations, especially progressive resistance, which is easier to achieve with a heavier, two-arm exercise. For example, advancing from a 25 lb. dumbbell to a 30 lb. dumbbell for 10 reps of concentration curls is a big 20% leap. But going from a 100 lb. barbell curl to 105 lbs. for 10 reps, is only a 5% advance, or, to better compare it to the concentration curl, 10% per arm. This is a good reason to do at least two, distinctly different types of curls in your biceps routine.

THE RUNNERUP  

It’s no surprise that the only machine exercise in the test, the cable curl, edged into second. With a weight stack moving vertically, gravity is always pulling, from start to finish, overriding our clock diagram. Because of its different stress application, consider including at least one mechanical exercise in every biceps routine.

THE LOSER  

We could’ve also predicted the free-weight preacher curl would lose. Again, it’s all about gravity. By starting each rep 45 degrees forward (the angle of the typical bench), these curls get hard fast. Imagine turning the clock above 45 degrees back, so 9:00 becomes 6:00. The forearm-parallel-to-the-floor red zone comes at the start, and then it just keeps getting easier.  At contractions, your forearm is pretty much perpendicular to the floor (175 degrees) with virtually no gravitational pull.

preacher curl

You can combat this by shortening reps (avoiding contractions) or by attaching chains to the bar to add tension throughout reps (as links come off the floor resistance increases). You can also (spider) curl on the nearly vertical side of the bench. And you can use a handle attached to a cable or a preacher curl machine, both of which feature vertically stacked iron fighting gravity all the while.

But those modifications are different exercises. What about the traditional, free-weight preacher? Should you just drop that loser for good? Nothing flunked this test. The five lowest scoring curls are just a few percentage points apart. All are valuable exercises. The preacher curl, with its anomalous starting and ending points, hits your bi’s uniquely, focusing more on stretches, less on contractions. People used to think this elongated the biceps. It doesn’t, but you’ll probably feel it more in the bottom of your bi’s.

Look again at the photo (by Gene Mozee) at the top of this article. That’s the original Mr. Olympia, Larry Scott, on the left, Freddy Ortiz on the right, O.G. arm-men, circa 1966. They did a hell of a lot of preacher curls. Larry did so many they’re still often called Scott curls. Include the best biceps exercises in your arm routine, but don’t totally scrap the worst one.

Related: Science Says: The Best (and Worst) Triceps Exercises