What can I do to improve my core?
Answer: Plank!
Plank is a fantastic Pilates exercise to massively improve your core - like all of it. Every bit of it. All the way round. Quickly.
But only if done correctly!
If you perform plank badly, or hold it for so long that you fatigue and slide from a great plank to a sagging droop, it can be quite dangerous.
Have a quick look at this video to set you up. Try holding it for just 10 seconds, and you'll realise just how tough it is. If you manage this, practice frequently adding a few seconds each time.