The reason people fall when a horse suddenly runs off (Also called Bolting) is due to lack of balance or being caught off Guard. Horses are big, fast, strong animals that can easily take a person down without meaning to.
A fall. Sudden dismount?
I have experienced this myself so I have a say, well when the horse darts forward, maybe cause you kicked or whipped him to hard or he got spooked, there is more reasons but the one when the horse gets spooked one is the most relevant, anyway you fall off because the horse can do it so intently that you can take it by surprise and fall off because of the sudden change of speed.
A sudden drop in the temperature
From a horse fall
The horse runs on a farm that it is raised at. The horse runs for about 20-30 minutes. Then the horse is ready to go!
a sudden fall of rain or snow
Normaly, horse riders/racers will fall off the horse. Someties it can cause bad injuries. Ride carefuly!
floods
Cascade
You should never make sudden movements near, yell at, shout at, startle, throw things at, or hurt horses. Basically, don't be stupid near horses. On Howrse it's don't return a hot horse to it's stall.
yes
Shies is the sudden movement by a startled horse. A startled horse may charge off at a fast run.