This is just me bored and rambling. But about Pulse??
A horse's resting pulse can be anywhere from 30-40 but at the rides they choose 64 most of the time as the maximum for moving on through what they call a gate. This gate is about 12 miles into the ride and when you come to it there are people there checking your horse and if you are above 64 you must wait until the pulse is below this 64.
I ride up to the gate and stop about 100 yards from this gate, get off, loosen the girth and lead the horse to the gate and he will be down below 64 so I call for a check. If he passes the checker writes a time on a score card. This is your in time, exactly 30 minutes after that time you can check out. There is a guy sitting at the check out gate, he takes your card and marks your check out time and won't let you move out until the time is up. You are free to stay as long as you like but most move out when then 30 minute hold is up.
During this time a vet looks at your horse checking like Painted horse said for lameness, unsoundness, serious wounds, etc, all for the health of the horse but he is not trying to pull you. He is looking out for the horse. He is your friend.
When you are free to leave you have the other 12 miles to cover for home, back to the trailer.
If you are doing a 50 you usually run the same 25 mile loop over again, same routine , only doing it twice..
A word on pulse. A working horse cruises as about 135 effortlessly. He can maintain this all day, he is not producing lactic acid, he is running on oxygen. If he starts working at above 150, say it is slighlty uphill, he is fatigued, the footing is heavy going, he is going lame, he is sick, etc.
He is working above his comfort zone and above 150 lactic acid starts building in his system and you have to slow down to prevent him from running into trouble.. I don't expect you to monitor him, to even know if he is running into trouble, just be aware that at the vet checks they are checking his recovery. If any of these things are building up he will not drop below the 64. Again to go out and have fun on a 25 you don't need this but to be competitive in the 50 a heart rate monitor really helps..
My guy could cruise at 135 all day and on some hills he ran 160 but going over the top it would drop to 110 almost immediately.
This is just garbage on pulse and not something you need to get caught up on the limited mileage.
Soon time to go home and go for a run on my boy