''All he did was spook and come round and I obviously came off over the front.''
As McKay was being dragged by her arm, the horse sped to a gallop around the racecourse at a speed that seemed like 150kmh, she said.
The trainer was conscious throughout the ordeal before eventually freeing herself.
''I wouldn't say it knocked me out, but it obviously knocked me senseless.
''Somehow I still had hold of the reins.''
McKay eventually freed herself and came to a stop on the back straight of the track near the stable of harness racing trainers Brent Shirley and Murray Brown, where she went to look for help.
''When I let go and I got up, I could hardly stand, and there was a hell of a lot of blood, so I took my helmet off. I tried to get back to Brent's to get some help and luckily he was there.''
After hearing McKay's call for help, Shirley got McKay into his car and got her to Kew Hospital, after assistance from Brown and his stable workers.
As she pieced together the events of Monday morning, McKay could not pinpoint at which point she received the blows that led to her injuries, and put them down to being freakish strikes that somehow got underneath her safety gear.
''I had a lot of safety gear on and I had ear covers over the ear parts of my helmet.
''That is why I was surprised I got this injury, because I can't see how the horse even got me there.
''The doctors thought that maybe it was my helmet that did the damage. It is fine, so it has got to be the horse hoof that has done it.''
Since being in Invercargill Hospital and then Dunedin Hospital, the former Mosgiel native had received an outpouring of support, and been joined by family, she said.
''That has kept me occupied all day: answering people's texts and Snapchats, whatever else goes - phone calls - it has been really good. Everyone has been really, very caring.
''I just appreciate all the help I got yesterday and all the (get) well wishes I got yesterday. It has been from all around New Zealand and it has just been incredible.''
The trainer has a good number of staff looking after her horses until she is out of hospital and she had received a huge offering of extra help, she said.