The basic standing curl, whether done with a barbell, EZ bar, cable or even dumbbells, is a great place to start on arm day, and for good reason. With a shoulder-width grip on the bar, you hit both biceps heads (long and short, aka outer and inner) about evenly. Because you can typically load it more heavily than other single-joint arm-flexor movements, it’s a good choice to do first in your workout.
But what if I told you a very simple change can put greater emphasis on the biceps peak, preferentially hitting the long head with a more significant training stimulus?
It’s important to remember that a muscle that’s fully stretched in the start position is capable of a stronger contraction than one that isn’t.
To do so, it’s important to remember that a muscle that’s fully stretched in the start position is capable of a stronger contraction than one that isn’t. (Think, for example, of how positioning your arms overhead during triceps exercises allows the long head to be better stretched and, therefore, to be able to contract more forcefully.) Whereas anatomically the long head of the biceps is located outside the short head, taking a closer grip on the bar allows it to stretch more fully – here, there’s more slack in the short head. This allows the closer-grip version to shift more emphasis onto the long head, helping you put more emphasis on your biceps peak.
Likewise, taking a wider grip on the bar shifts the emphasis to the short head. Here the tension on the long head is reduced in the stretched (start) position, while the tension on the short head increases. (It should be noted, of course, that you can’t isolate either head, but you can alter the training emphasis.)
How close is close and how wide is wide? If you consider a shoulder-width grip to be neutral, then going inside (about hip-width apart) is regarded as close and a few inches outside your shoulders is wide. You don’t need to – and shouldn’t – take extreme hand positions.
You can selectively do more close-grip curls to bring up your peak, but you might also consider a strategy of using both wide- and close-grip curls in your workout to maximize overall arm size. I often do two working sets of each hand position as a way to hit the most possible muscle fibers.