Ok let's take a look at what he did incorrectly in the video. Remember, that prop is a meat grinder just looking for something to chew up and it does not care what that something is.

First thing is the plane is not tied down:

Even if you are alone, never ever start up without the airplane secured. Imagine leaving the throttle wide open or even partlyopen and the engine starting and not having a really good grip on the plane.

Second thing:

Take a look at where the radio is. Yep, right in front of the prop. Again the engine is now running and he is taking it to full throttle, holding onto it with one hand while the other is working the radio.

Third thing:

After starting he remains in the props arc with his right arm and most of his body while testing the engine at full throttle.

Let's say the engine starts but is running in reverse so he blips the throttle while holding onto the plane with his right hand and now the engine throws the prop due to the sudden direction change. I know you are going to say that it's changing direction in a way to not toss the prop nut but I have personally experienced an OS160 where I blipped the throttle, the engine kicked to turn the proper direction and then kicked backwards only to toss the prop off which proceeded to stick itself in the leg of the table right next to the plane. I learned at this time to shut down the engine if it's running backwards and restart it. Thankfully I was no where near in the props arc when it tossed it and the next closest person was quite a few feet away.

Lots of people have made really good suggestions about the safe way to start and test the engine before flight. What I have found that helps me is to ask yourself this.

How can I start and test run the engine while reducing the time that I need to be in front of the prop or reaching over the arc of the prop.

Those 2 items alone will help you be a safer pilot in regards to engine/prop proximity. Even with a plane tied down, sometimes you must reach over/around the prop to hold the plane, especially if you are using a starter. What you want to do is minimize that exposure time.

I've seen a member with years of experience make the mistake of bumping the throttle stick to half throttle, having the plane tied down but with some slack in the rope and the engine fire off and go to high rpm and jump towards him. This member instinctively reached to stop the plane but unfortunately reached right through the prop.

38 stitches on the top of his hand and 57 stitches on his forearm later he was still chewing himself out for not checking everything before startup. Thank god there were tons of people there that were able to help him and get him to the hospital quickly.