Certainly the most ridiculous trend in core training, and abuse of its equipment, has been the notion that you should perform all your exercises on the Bosu ball. The theory behind this is that your core will work harder as your body struggles to balance itself on top of the ball. While this kind of training does make any movement more difficult to perform, it prevents you from using anything approximating a heavy weight, so your muscles go unchallenged.
You will not build any muscle or strength this way, and your core will never be conditioned to handle the stresses of tough workouts or sports. Unless you're training to improve your performance during an earthquake, exercising on an unstable surface offers no real advantages.
Ultimately, doing so will leave you weaker and more at risk for injury. To truly tax your core, keep your feet on a stable surface, and train with time proven simple exercises such as those given here.
A steady regimen of multi-joint, freeweight exercises like the squat and deadlift should build your core along with the rest of your body, but these supplemental core exercises are what you need to truly pass the plank test.
Learn them all and cycle them in and out of your workouts from now on.
They are:
1. PLATE RAISES
2. ONE-LEGGED DUMBBELL ROWS
3. SUITCASE SQUATS
4. OVERHEAD SQUATS AND LUNGES
5. ONE-LEGGED SQUATS
I will provide more detail on the above exercises in my next segment.