If you think of building muscle as basically just sets and reps and weights, you're not wrong.

But to fully activate every last muscle fiber and stimulate a muscle to grow, you have to make it contract at different lengths. That's why it's so important to train with a variety of exercises that work muscles from different joint angles. With this workout, you'll play all the angles to build your arms in just four weeks.

How it works

You'll begin with the one-arm cable biceps pose. While it may look like an exercise for, well, "poseurs," understand that when the arm is raised to 90 degrees and the elbow is flexed, the biceps are put in their shortest position. When held for up to six seconds, this increases your nervous system's activation of the biceps, leading to better contractions throughout the rest of the workout. 

The next exercise, the cable crossover triceps extension, accomplishes the same thing for the triceps. From there, you'll work the biceps and triceps with moves that train them in their most stretched positions. Changing the length that the muscles must work at changes the tension in them and, ultimately, the amount of muscle fiber that gets worked. And while it's harder to understand than "three sets of 10," you arms will get the message: Get bigger!

Directions

Perform the workout once per week. Exercises that are paired (marked "A" and "B") are alternated. So you'll do one set of A, rest as prescribed, one set of B, rest, and repeat until all sets for the pair are completed.