Alright guys, today we're gonna take a look at a video with half a million views (but why?). Mr. O teaches us how to get "full fullness in these biceps"!
21s are widely used in bodybuilding circles. Which is fine. Only problem is the way they are executed doesn't make any sense if you know anatomy and biomechanics. 21s are nothing other than a mechanical drop set. With mechanical drop sets you're not changing the load, but you're changing positions to fit the resistance profile of the exercise.
As Phil Heath demonstrates in the video, the first 7 reps are partial reps in the bottom. That's the part of the range of motion (ROM) where you are strongest.
He then does 7 partial reps "at the top". This is where you are weakest.
Phil finishes the set with 7 full ROM repetitions. This is where you work the muscle over it's full ROM of that exercise. The resistance profile looks like a bellcurve, with the mid-range being the hardest (when your forearms are parallel to the ground).
I don't know about you, but nothing about this set makes any sense. This is a poorly designed mechanical drop set. And everybody who does 21s performs them like this without thinking.
Think this stuff through.
Don't just copy something because Mr. O or the big guy at the gym does it.
1) Perform 7 partial reps at the top. This is where you're weakest and if your elbows travel forward slightly your biceps is also partially shortened via the shoulder joint, which makes sense in this case.
2) Perform 7 FULL reps. You're now training the mid-range where you're stronger than in the shortened position. Plus you can use some momentum to overcome the resistance when you're forearms reach parallel (not encouraging cheat reps btw).
3) Perform 7 partial reps at the bottom. This is where you're strongest. Since you're already fatigued, putting this ROM here makes the most sense. For the same reason putting it first, makes absolutely no sense.
Generally, 21s suck. There's nothing special about them and most exercises are not fit to train a muscle over all 3 ranges. This is one of those things in bodybuilding that'll probably never die.
Do a triset of exercises that put you in the perfect position to produce force in their respective ROMs.
Exercise 1 (shortened): Hercules Curl (curl towards the back of your head),
Exercise 2 (mid-range): Regular Barbell Curls,
Exercise 3 (lengthened): Incline Dumbbell Curls.
I guarantee FULL FULLNESS IN THESE BICEPS with this routine. And don't forget: 21s suck.