Preexhaust, the technique that has you train with isolation exercises before multijoint exercises, is effective for inducing gains in muscle size.
Brazilian researchers had men from the Brazilian Navy Sergeants School follow a weight-lifting program twice a week for 12 weeks. One group performed exercises in the following order: bench presses, lat pulldowns, triceps pushdowns and barbell curls. A second group performed the exercises in the opposite order. A third group did not train at all to serve as a control.
As reported in a 2010 issue of the Journal of Sports Science and Medicine, the group performing the arm exercises (isolation exercise) first in the workout increased their triceps muscle size by about 10%; the group performing the multi-joint exercises first and the arm isolation exercises last had no change in triceps muscle size.
The results of this study suggest that the triceps respond better to doing isolation exercises first and multi-joint exercises later in a routine. The triceps may have grown when subjects did triceps pushdowns before bench presses because the triceps were fatigued when they performed the bench press. This allows the triceps to get more of a workout on the bench press than when they are not fatigued and the chest mainly takes over.
Consider using preexhaust training to stimulate some new triceps growth. Start your triceps workouts with triceps extension exercises, such as triceps pushdowns, overhead extensions and lying triceps extensions. Finish with pressing exercises, such as close-grip bench presses and dips.