Jane Christian replies....Basically the answer is yes. However, initially the rider cannot easily isolate the core muscles and a lot of heaving and puffing is involved which makes it hard to maintain. Your other point is very important....it is the concentration that most riders lack and need to develop. The amount of muscle tone and concentration actually used by 'talented' or professional riders is far, far more than the learning rider can even imagine. That said, there are many other areas where bringing up muscle tone actually help 'support' the tone in the core muscles. These would be the muscle chains running down either side of your body and it helps to think of them coming inwards throughout the length of your torso so they meet towards the middle. This is especially important if you have a slight asymmetry, or curve to the right or left. Keeping the muscle tone up in your thighs, almost as if you are balancing a tea tray on your 'lap' and thinking of keeping the ball of the ball and socket joint of your hip going inwards towards the socket. It all goes towards making your torso, pelvis and thighs stiller, more stable and therefore easier for the horse to balance and bring up his back. See if you can get a copy of Mary Wanless' latest book - from Basics to Excellence - it will really help you.