SETUP: Lie flat on the floor underneath a Smith machine. Position the bar two or three notches high to give yourself room to grab hold of the bar (see video). Take an overhand-grip of the bar. This is important, because an underhand-grip wouldn’t allow you to push into the bar to control the rep anywhere near as much.
REP: Push your hands into the bar, tighten your abs and pull your legs up in an arc-like motion until your butt comes off the floor and your knees are close to your chest. Control the negative (lowering) phase of the rep, don’t just drop down
TIP: I like to breathe in before starting the rep, then breathe out as my legs are coming up. Then I breathe in again at the very top, before breathing out all the way down. The control which the Smith bar brings should see you get some excellent slow negative reps here.