Many professionals and personal trainers will tell you that the key to developing mass in the triceps muscle is an exercise suggested by the great
Larry Scott, the mass-developing kneeling long-cable triceps extensions using a special triceps machine with tiwn or v-shaped pedestal benches to
lean on. Several exercises are good builders of the long head, but none is as effective as Larry's kneeling cable exercise. First, let's look at
why you need to develop the long head to get big triceps and big arms. Two-thirds of arm size is triceps, so their development is a priority
for anyone hoping to build a pair of huge guns.
The long head of the triceps is by far the biggest of the three heads, and has the potential for the most size. Naturally, you should give the long head lots of work in order to fill your arms out.
When a bodybuilder has huge triceps, you'll notice that they hang down like the underside of an overfed shark in certain poses - e.g. the front double biceps. From the side the arm hanging down looks very thick and wide. Big triceps are to the upper arms what big hamstrings are to the thighs.
Oddly, few triceps, machines or even triceps exercises directly target the long head except for the kneeling cable triceps extension. Even the popular triceps pushdown scarcely works the long head at all because it is not attached to the humerus bone, as are the external and inner heads of the triceps. Instead the long head is attached to the super glenoid tubercle of the scapulae (back of the shoulder).
The type of exercise you do and the position of the elbows makes a great difference in targeting the long head. The triceps must be prestretched in order to get a full contraction. The muscle has to go through a complete range of motion, full stretch to full extension. To get this prestretch, your elbows must be above your head. The kneeling cable extension with pedestal benches stretches the long head more than any other exercise. With your body anchored and your elbows firmly placed on the pedestal benches, you can get a very full range of motion, a lot of stretch at the beginning of a rep (as long as you let the cable pull your arms back as far as possible), and a very intense contraction. It really isolates the triceps perfectly.
So what's the alternative to Larry's pet exercise? One is the seated overhead triceps extension with an EZ-curl bar. The problem with the barbell is that a lot of stress is placed on the elbows, especially if you try to use very heavy weight. The elbows are in such a vulnerable position that you must be very careful to avoid injury. At the first sign of any strain or pain, stop the set immediately - even if you've done only l2 reps. I would definitely make this a medium- to high-rep exercise - say, 10 minimum and 15 max.
You can also do seated overhead triceps extensions using the bottom pulley of a cable crossover machine. You'll need a training partner to hand you the bar and return it to the starting position at the end of the set, but this exercise is worth the extra effort because the cable version is easier on the elbows than the barbell version. Your partner can push on your elbows to stabilize them and help you get more triceps isolation.
Another decent long-head exercise is the seated French press with a single heavy dumbbell. Having a partner to do this exercise is helpful but not always necessary. Remember to keep those elbows pointing up and get as much stretch as you can at the bottom of the movement.
A final alternative would be the one-arm dumbbell or cable extension. Do 'em seated with the elbow of your the working arm close to your head and pointing at the ceiling. Use a full range of motion. If you 're well warmed up and your elbows feel good, you can go pretty heavy on this exercise (6 reps), especially if you do it first in your routine. Otherwise, and particularly if using it as a finishing exercise, I would do moderate to high reps (10 to 20) and go for a real burn and pump in the triceps.