way i see it, the truth is (as usual) somewhere in the middle.
Muscle shape and size may mostly be genetically determined, but it is the way you train your muscles which determines how much and which parts of your genetic blueprint will show developement.
I do noticed more 'peak' development when i incorporated concentration curls and scott curls.
You cant develope a peak that is not there, but you can forget to develope a peak that may be there....
I say hit your muscles from all angles, starting with the basic bread and butter compound movements first, for 8-6 reps and the so called shaping movements for 12-10 reps after that.
Doing heavy barbell curls before concentration curls will in time yield much more biceps strenth than doing concentration curls alone and you will be able to do heavier concentration curls (now you're making some real progress)
Like one of the other posts said: "Science may have found that 10-8 reps is the best range for hypertrophy, and 6-4 reps for strength, but i find it hard to get stronger on 10 reps, so i do 8-6 reps"
10 reps ARE ok if:
- you are on juice, which will help you to do that many reps with substantially increased weight, and help you recover faster from the taxing tissue damage.
- you have done a powertraining cycle with low reps, you have become stronger and now wanna get rewarded with muscle size
- you've done the basic power movements in your workout first with 8-4 reps