We all know how it goes. The biceps are the least appreciated muscle when it comes to a lot of traditional strength programs. In Starting Strength, Rippetoe remarks that since you're going to be doing bicep curls anyway, he might as well include them in the book and teach you how to do them right, though he wouldn't have normally. You might see some biceps work in assistance for bodyweight routines oriented at calisthenics or gymnastics trainees, but outside of that it’s rarely used. The big guns that you like to see on bodybuilders are shamed by many other corners of the fitness industry.
The problem with this is that the biceps can often be hugely useful muscles. When it comes to the traditional bench press, training the biceps can help improve stability in the lowering phase of the lift, and regular training of the biceps can help keep the elbow joint in good working order. This will be particularly useful to powerlifters. In pulling lifts such as rows and pullups, the biceps will directly contribute to the lift. Lastly, carries such as the kind frequently seen in strongman events often require sustained elbow flexion and thus benefit from added biceps strength.
With this in mind, what’s the best way to train your biceps to have maximal carryover to these activities? Well there’s a simple answer and a complex one.
The complex one is this: no exercise is ever a complete solution, and variation in your program is often necessary to maximize performance in any particular lift. This is why we don’t just squat over and over again all the time to build squat strength - it’s certainly one way to do things, but chances are that it’s not optimal.
So the complex answer is that you should stress the biceps in a variety of different ways. Traditional barbell or dumbbell curls will build strength and muscle. Preacher bench variants may be less useful as they involve less stabilizing challenge to the elbow. Cable curls help stress the biceps through a different force curve. Hammer curls will target the forearm musculature as well as the bicep, and reverse curls will target the forearm musculature even more. Using all of these tools will help you ensure that you get the best out of your arm workout.
However, at the same time not everyone has the time or the equipment to do a lot of sets of bicep curls. Further, it would absolutely be a waste to allow a very diverse bicep routine to interfere with your primary strength training, which would diminish the point of working out your biceps as an accessory movement anyways. So ultimately, simplicity may be your best option here. A simple workout with a lot of bang for your buck will often trump a complicated one with a lot of possibilities to go wrong.
With that in mind, the simple answer is this: hammer curls.
Hammer curls have two major advantages over most other biceps exercises:
One is that they engage a great deal more of forearm musculature (which would often be neglected otherwise) than the traditional bicep curl. Since all elbow flexion is a combination of biceps and forearm musculature, and when we train for strength we’re training for movements and not individual muscles, it only makes sense to use the hammer curl to strengthen that elbow flexion maximally.
The second major advantage is that the hammer curl is often more specific to major motions. While I’m not arguing that a bench press uses a hammer grip, for example, I will point out that the hammer grip is more like the bench press grip than the traditional curl grip is. (The traditional bicep curl grip is more like the reverse grip bench press.) If I had to choose a second most useful biceps exercise, it would be the reverse curl and for this same reason. Holds and carries will typically be done with a grip on the implement more resembling a hammer grip than a traditional curl grip.
When I trained at Westside, hammer curls were the only biceps exercise that Louie allowed trainees at his gym to practice, and in this I tend to agree with him - most of the training I do for biceps is either the hammer curl or the reverse curl.
Being strong doesn’t mean you have to cut out the biceps training that gets you the guns you’re looking for - it just means training your biceps in the most useful way possible in the context of your strength goals.