Classification
| Type | auxiliary |
| Mechanics | compound |
| Direction | pull |
| Equipment | flat bench |
| Additional Equipment | - |
Instructions
Preparation
Lie in flat supine position on flat bench. Let legs hang straight off one end of the bench. Extend arms above head and raise head slightly.Execution
Pull legs and arms simultaneously up until legs are positioned about perpendicular above hips. Maybe let hands and legs touch slightly. Raise torso up while lower back remains on bench. Return to starting position with controlled speed and return.Variations / Comments
Jack Knife is quite a complex exercise that requires some training experience along with a certain hip flexibility. The slower Jack Knifes are done the harder they become.
Starting Position 
Ending Position Muscles
| Target | Rectus Abdominis | Hip Flexors |
| Synergist | - |
| Stabilizers | Obliques |
Front
Rear
