Ya know, you didn't specify which section of your back is weak, lats, traps, lower, mid, so that might help if ya, did. Won't matter, really, though, cuz it was pretty much covered completely already.
I did this yesterday. 70lb concentrated dumbell curl. I use my other arm to assist to ensure correct form and it also enables me to go past failure. On speed day I would do the same exercise.
I usually do 8 sets but being biceps are a smaller muscle group I normally do around 5 sets.
Goal:
To move the weight as FAST as possible from point A to point B with perfect form.
grab as many plates as you can possibly handle and do with decent form hold them in your hands and do weighted back extensions....wicked wicked lower back strength and hamstrings from this. Not to mention your erectors get jacked...
I do 5 sets wide grip pull ups, 4 sets Lat pull down, 4 sets bent over barebell rows, 4 sets one arm dumbell rows, and seated cable rows. Am I missing something here anyone have a good back workout because my back is a little weak would like to have a little more intense back workout. Thanks.