The are many exercises that will make your muscles burn. The question you have to ask yourself is, "will these exercises transfer over into real-world benefits.
The six movements listed below will target all components of the muscle groups that make up the "Core". These will transfer into helping improve your athletic performance because they simulate certain requirements of most sports (stabilizing under load, rotation, and resistance).
This circuit does not have to be completed as fast as you can. Just move through the exercises briskly and comfortably. Try to limit rest between movements to 10-15 sec at most. Once all are completed then allow 1 min to recover and stretch if needed.
Can you make it through all without having to rest during each exercise, and during each set? Don't worry, these are small muscles and fatigue pretty quickly. Do your best and enjoy.
15x Barbell/AbWheel Rollouts
30x Med Ball Russian Twists (10/14lb)
30x Hanging Knee Raises
15x Back Extensions
30x Slow Mtn Climbers (total)
30x Sec. Plank