First off - I have two four year olds, started them both myself and have done all of their training. My warm up consists of walking on a loose rein for 5 minutes, then an easy trot for 10 minutes on a long rein, then I walk for two minutes, after which I pick up contact and get down to business. As far as cooling down after their work out, I cool down on top of them at a walk on a long rein for at least five minutes, with another 5-10 mins of hand walking, depending on how hot the horse is (they are in reasonably good condition, ridden 5 days per week), but I never stop until the horse's breathing has come back to his resting rate. Not sure if that's above or below the average warm up for a schooling session as it's been YEARS since I rode at a barn.
The other reason I'm asking is because I have these neighbours, and they have this routine about once every two weeks that makes me cringe. They have four horses, all fat and VERY out of shape. One gets a ten minute ride down in the back pasture once a month in which he spends more time eating than actually moving and I don't think he's even been kicked into a trot for 6 months, and the other ones, well, they've literally been ridden once each in the last twelve months. They do however get what I call their '5 Minute Work Out'.
What they do is chase all four horses into their little outdoor arena at once. Immediately they get out the lunge whip and start cracking it in every direction. The horses gallop around in the dust and mayhem for 3 or 4 minutes tops and of course they are all huffing and puffing and looking like they are going to drop over dead. Then the owner walks away, comes back in half an hour and throws them back in their paddock. Absolutely no warm up, no cool down, I think it's pretty much akin to abuse myself. We don't have an amicable relationship.
So how prevalent are heart attacks in horses? Would you expect one in this scenario - none of these horses are overly young - they range from 12-18 y.o. What else would you expect to come of such a scenario? Pulled tendons? Who knows, they could already be lame, but the owners would never know it because the horses NEVER move except to be chased around by a mad person with a whip in a dusty arena going in all directions at once for more than three minutes!! I'm rather worried for them.
Who knows, probably nothing. Heart attacks in horses happen but not that often and usually theres an underlying condition that causes it. I've know a couple horses to have heart attacks just standing in the pasture. One was only 8 years old. Theres nothing you can do about it so don't worry about it. Unless you are friends with them and can talk to them about what you do and maybe they'll take the hint.
Horses aren't our whole life, but makes our life whole
I'm pretty sure I don't see any horses 'warming up' or 'cooling down' when they spook, bolt, and charge around paddocks and fields. At many medium to large sized farm there are probably a few horses bandying about like nitwits at any given point for one reason or another.
Whatever the motivation, even if someone notices the equine dramatics immediately, hiking to the pasture to fetch the darlings and then having them drag you back to the barn (whilst schooling their in-hand piaffe/passage, if not levade/capriole) is about a 5 minute affair. Unless the horse is EXTREMELY hot (dripping, lathered, veins exploding, nostrils strained to the extreme) very few barns would spend the time hand walking the horse to 'cool down.' Generally, the aspiring Airs Above the Ground performer is stripped of boots and fly mask and tossed in the stall.
Sound like what your neighbor is doing is not much worse than what horses do every day in turnout in many/most/damned-near-all boarding and training barns.