1. Side bridge. Laying on your side, raise the hips up with your weight on your feet and elbow. Hold until failure. This improves the endurance of the lateral musculature.
2. This requires a box with an incline of ~55 degrees. Get in a sit-up position with the back against the incline and with the feet secured to the ground. Have someone pull the box back a few inches. Support yourself as long as possible until any part of your back touches the box. This improves endurance of the flexors.
3. The upper body is cantilevered over the end of a bench or table with the feet secured. The arms are held across the chest with the hands on the opposite shoulders. Failure occurs when the body drops below horizontal.
4. Bird-dog exercise. Starting on your hands and knees, raise one leg and the opposite arm out to horizontal and hold for ~10 seconds at a time.
5. Curl-up. NOT a sit-up. Lie on your back with one leg at 90 degrees and the other flat on the floor. With NO cervical or lumbar flexion, lift your head an inch or two off the floor and hold.
>3. The upper body is cantilevered over the end of a bench or table with the feet secured. The arms are held across the chest with the hands on the opposite shoulders. Failure occurs when the body drops below horizontal.
This short 3 min video from the New York Times features four core exercises that protect the spine. It's narrated by the same Stuart McGill mentioned in antognini's post
All other thing being equal, a stronger muscle will have more endurance than a weaker muscle. The reason is quite intuitive: the same load is a smaller percentage of total strength for the stronger muscle, and thus less fatiguing, than it is for the weaker muscle.
