Your problem sounds exactly like a friends. Her horse had stress induced
narcolepsy, and it only occured occasionally. Stress is caused by a
whole bunch of factors not just heavy exercise. When you are in training
I'm assuming you are on familiar trails, either alone or with a familiar
horse, and you go back to the barn when finished (safe haven). Heavy
exercise may not be enough to stress your horse out at home. A race is
something quite different (we are all aware of that).
When you are at a Pand R station try to find something to distract your
horse while the check is being performed. Get one of those little
cricket toys and snap it in his face. Put a carrot in view, but out of
reach. Don't feed it while the check is going on, that chewing can be
hard to hear through! Rub his forhead with vigor. In other words, don't
let his brain go to sleep.
Keep in mind that there are other things that can make a horse lose
conciousnous - heart problems (P and R people are not vets and unless
they know what to listen for will not be able to pick up an occasional
anomaly), circulatory problems, brain tumors, etc. My friend chose not
to medicate her horse (very expensive) and had ten good years on him
before she had to put him down. Your best bet is to have the tests done
and decide what to do from there.
Good luck,
Tori