HOW TO DO IT: 90-DEGREE EXTENSION
Ninety-degree back extensions done for reps are a challenging exercise for all your squatting and deadlifting muscles. Holding them for time, however, is a great measure of core strength endurance. If you can’t make it at least 60 seconds, practice back extension holds first thing in your workouts until you can. You’ll reduce your risk for back pain and see stronger, sharper abs.
Keep your core and glutes engaged when doing any back extension. Your torso should be straight at the top position, not overextended.
1. Climb onto a glute-ham bench and secure your feet. Make sure the pad is about midway down your thighs so that you have room to move at the hips.
2. Squeeze your glutes and extend your hips to raise your body until it’s parallel to the floor. Hold as long as you can. Don’t arch your back or look up.