The biceps muscles were given their name based on how many parts they comprise. These muscles are actually called biceps brachii, which translates to two-headed muscle of the arm. Those two muscle heads, or parts, are the inner and outer head. You can choose which part to focus on during your workouts with a few neat exercise manipulation tricks. Bear in mind that you will work heads at all times, but place more stress only on one head using these techniques.
The barbell curl is the meat and potatoes of any arm training regimen. Bodybuilders treat this exercise as the staple for building the mass of their inner and outer biceps. And you can do the same. Simply hold a barbell with both hands in an underhanded grip and stand up straight with the barbell hanging in front of your thighs. From this starting position, bend your arms as much as possible and squeeze your biceps as hard as you can. Don't hold your breath. Inhale on the way up and then exhale on the way down. Do three sets of 10 to 15 reps of this and any other biceps exercise in your routine. Don't exceed more than three inner or outer biceps exercises per workout.
Go Wide or Go Home
Okay, so you know that barbell curls are king for biceps mass-building. But, there's more to this. If you want to get those inner biceps to bear more of the workload, then opt for a wider hand grip. Go as wide as you comfortably can. This means if your hands are all the way at the ends of the barbell and you still feel comfortable while doing the curl, then by all means utilize this wide grip. The take away message here is the wider your grip, the better. But, if you feel uncomfortable, then lessen the distance of your hands.
Back Those Elbows
You've probably seen at one point or another a big bodybuilder at the gym swinging a barbell over his chest to complete each and every barbell curl repetition. This common practice among lifters is plagued with injury-risks. But it also means less inner biceps involvement. The more your arms are raised in front of your body, the less your inner biceps can contract. This is due to a biomechanical principle called active insufficiency. Just understand that you must keep your elbows as far back as possible at all times while you pump out those barbell curl repetitions. Your inner biceps will thank you later and so will your lower back for that matter.
Incline Dumbbell Curls
To take this last technique to the next level, you should position your elbows behind the line of your torso. You can't do this with a barbell, so you'll need a pair of dumbbells. You'll also need an incline-angled bench around 45 degrees so you can lie back and get your elbows back behind your torso. This exercise is called the incline dumbbell curl and its effect on the inner biceps is an increased stretch throughout the range of motion. More stretch equals more muscle activation. And more inner biceps muscle activation will lead to better results over time.