This
one is a variation on the classic
"leg raise" exercise...the
key difference here lies on WHERE
you're doing the exercise.
It's
not a hanging version - it's actually
a fair bit harder than that!
With
this version, you're going to be supporting
yourself on the safety rails of the
power rack - it almost looks a bit
like the Iron Cross position a gymnast
gets into on the rings.
So first,
set the safety rails on the rack to
about the level of the bottom of your
rib cage - you can adjust height any
time.
I like
to set the height so that I can set
my hands on the rails while in a standing
position, then bend my knees to get
my feet off the ground. I find this
to be easier than trying to jump up
in order to have straight legs at
the bottom.
The
arms should be about 45 degrees at
the shoulder.
Set
your hands on the rails and hold on!
Bend your knees and get your feet
off the ground. You will instantly
feel big-time tension in the abs and
torso because of how you're supporting
your body in this position.

Now
we add in the leg raise...

You
can also do it as a knee raise...

I like
to start with the straight(ish) leg
raise then as I get tired, switch
to the knee raise in order to keep
going.
This
one is BRUTAL because not only are
raising the legs (which involves the
abs in a movement capacity), you're
also involving the abs very strongly
in a supporting capacity.
Give
this one a try in your next ab-training
session (do it first, before any other
ab exercises - trust me on this -
you probably won't need to do any
more abs after a few sets of this).