Hey, i'm going to guess that your horse is of the kind that would rather stay still and eat than do stuff most of the time. And I also guess he prefers to go slow than fast. If so its about motivating him to put effort in it.
So, you start from the ground with one or two ground poles, you have him walk over it while staying in the center of the circle and his task is to pass the pole/s without touching them. If he does, he repeats it until he doesn't touch it. Whenever he passes them without touching them or touching them less than the previous time, you stop him right after and let him stand and rest. Then you can try at trot, he will associate the putting the effort to look where he goes to rest and therefore try harder. Keep going until he tries.
Is this when your lunging or rideing
My trainer wants to hit tap his legs with the poles to teach him that they cant be touched so I may try that.
I have tried to raise 3 and have 3 on the ground but he completely crashes through them, it is almost funny now because he is a great jumper.
If there ground poles try raising some and leveing some on the ground make things interesting and difficult if he's likes to be tested