Answer

By Your Horse

Dressage rider and trainer Claire Lilley says…

Make sure you’re not transmitting tension to your horse. If you’re tight in your fingers and wrists, he could be reacting and resisting against you.
Lengthen your reins long enough for him to stretch his neck forwards, but not so loose they are flopping about. You must hold the bit steady – you can’t do it with tense hands.
Sit tall in the saddle on your seat bones, with your hips upright, legs down against his sides, elbows in, shoulder blades together, a firm stomach and back muscles – so you feel like a tree trunk around your middle. Your horse will need this stability
to lift his back underneath the saddle and tuck his pelvis under.
Remember, being ‘on the bit’ starts from the horse’s back and then his hindlegs before he softens his neck and relaxes his jaw, accepting the rein contact.
Exercises to try are half-halts, walk-halt-walk exercises and, later, trot-walk-trot.
Make sure each set of transitions works before moving on to the next.
Using ground poles will help him use his back properly – by keeping your hands still either side of the pommel of the saddle, your horse should find his own contact if you’re riding him properly from your legs.
Avoid pushing with your backside. Poles will help you to feel how he moves his back muscles and coordinate your hip movement with that. Only then will he relax and accept a contact, chewing quietly ‘on the bit’.