Anchor your feet under something and lean back until you feel your abs turn on. Try to keep your spine and neck as neutral as you can. You can go light and do the exercise for 60 seconds, or use heavier weights and shoot for 12-15 reps.
Maintaining the half sit-up position while performing any movement with the arms will challenge the abs, hip flexors, and even the neck muscles.
In today's training world, most experts would agree that high intensity interval training (HIIT) performed after resistance training is the best way to get lean.
We can always count on Christian to give us some great new movements that, in addition to spurring new muscle growth, will elicit bewildered stares from all the ACE certified trainers in the gym.