Hanging leg raises

Grab a bar and just hang, let the momentum disappear and do nothing until your body is still and the legs are straight.

Flex all your muscles especially your Lats, Abs, and muscles surrounding your elbows.
Slowly raise your feet up to the bar, remember to keep your legs straight.

Lower your Legs and Repeat.
The duration should be slow so as to use no momentum, try 5 - 8 seconds up, 5 - 8 down.