This seems a little suspect to me. Surely the dogs can be trained to stop when there’s no load, or when the mushing stops, or when they hear a specific shout or whistle from the fallen passenger, right?
I remember watching that episode. He purposely fell off and like he said, the dogs kept going. As to whether they can be trained to detect that you’ve fallen off and stop, or stop when the mushing stops, not so sure…
My dad (and expert Alaskan musher/dog sled driver) said more or less the same thing- if the dogs “were going full out it’d take them a while to figure out you weren’t back there, they loved to run so much that some teams might not stop until they wanted mush” (Mush is the food fed to them). He depended heavily on a super smart, loyal and assertive lead dog. Named Kazan, of course.
He used to scoff about dogs being trained to go on the command “mush”, as as far as he was concerned, that’s what a musher would say when he was teling the team it was dinnertime as soon as they got home, so they’d speed up. He said “Let’s go boys.” “gee” “Haw” were commands for turns. He also used the term “dog sled driver” more than musher. He actually had the MoS of “Dog sled driver” in the 10th Mtn Div in WWII, so he’d likely know.
Says.
I don’t know anything about whether or not they stop, but we have sled dog races here every winter - it’s a pretty big deal. And they call them “mushers” in that event. I’ve never heard any complaints…
Yes, true- now. But that’s some 7 decades later after the “musher” meme became popular. Dad ran Dog sleds *before *WWII.
DrDeth, your dad had the coolest MOS ever! 
What DrDeth said. I mushed dogs in 10th Search & Rescue in Alaska in '46 & 47. True, not only did you never have to yell “mush” to get the dogs started, when harnessing them up, you had to be sure the sled was tied to something, or they’d be long gone. When ready to start, you untied the rope and hung on for dear life. Often the sled became airborne for a few seconds as nine malemutes shot out at full speed. I never knew how the term “mush” came into being, as never heard any Eskimos or others use it. Probably a Hollywood invention.
If you fell off, it would be a long time before the dogs decided to come back and see what was wrong, if ever, I think, but don’t know as never knew it to happen.
There is a good reason they have a brake on the sleds, a lever with some iron hooks. You step on that and it digs into the snow, and eventually the dogs may stop.
There is absolutely nothing they love to do more than run!
So, if you are going to try dog sledding, keep a firm grip on those handles. 
I don’t know about the dogs, but I used to skitch with my girlfriend. She would be on her rollerblades and me on my bike. If she let go and didn’t say anything, I wouldn’t even notice she was gone.
Yes, but there still is a load.
In actual use, the sled is loaded with many pounds of supplies. So that the human is only a small portion of the load. A common rule of thumb is 100 pounds (45kg) of freight per dog. Thus a 9-dog team might pull 900 pounds of freight, the sled itself (about 50 pounds (22kg)) and the driver (say 150 pounds (67kg)), for a total weight of 1100 pounds (500kg).
The driver is only about 13% of the total weight; if he fell off, the dogs might not even notice it.