This is a
unique exercise for hitting the forearms - it looks
almost like a regular preacher curl but done gripping
on the plates of a dumbell instead of the handle.
It'll involve
the biceps and brachials somewhat (when you do the curling
part of the movement), but the primary focus is the
forearms.
So first,
get a medium-weight dumbell. It's best to use the db's
that have flat plates - it'll still work with hex head
dumbells, but it's a bit tougher to grip and you'll
need to use lighter weight. I'm using a 65 lb dumbell
here. The heaver the weight you use, the thicker the
grip and the harder it'll be so choose carefully.
Set the dumbell
on end on the top of the pad then set your hands under
the plates of the top end.

Now get into
the bottom position...your fingers should be under the
plates and your thumbs should be on top, squeezing the
plates with your grip.

Now curl
the dumbell up. Grip the dumbell HARD to hit the forearms.
The weight you're using won't be too challenging for
the biceps but it will put a lot of tension on your
forearms, to keep the dumbell pinched.

Now you're
near the top. The dumbell will be tilting away from
you.

Finish the
movement by pulling the dumbell to a vertical position
- this is another forearm movement (like a wrist curl
type thing).

So when you're
doing this exercise, you're hitting the forearms isometrically
during the curl and with an actual wrist curl movement
at the top.
Repeat for
as many reps as you can until you feel your grip starting
to slip on the curl up.
Now you'll
rep out with the wrist curl portion at the top. Keeping
your forearms vertical, let the dumbell tilt forward.

Then pull
it back up to vertical.

Keep going
with this until your forearms are toasted.
This is a
great combination exercise for really trashing your
forearms and grip strength.