The opening of the show explains the show best. It is taking non-military civilians that volunteer to undergo a brief sampling of what U.S. Special Operations Forces go through for their training.
It is not meant to be the real training nor is it to the same exacting standards. People can stop and quit when they want. The instructors can also medically disqualify a person if a medical issue arises that will threaten their life later or if it will keep them from completing later stages of the training.
The tasks folks are exposed to are very realistic. Someone pointed out that having women also on the show is unrealistic and I can say from personal experience that some women can handle it for sure but that does not mean they would be able to handle the real thing when you have to have on not 35 pounds of gear but 200 pounds and up of equipment.
I know of one woman that tried in real life and she didn't get past the 1st phase of selection; but, that like I said was in real life. This is a show with a different purpose and the women on it are doing as good a job as the men.
What I am loving about the show is that it does show how important the mental side is as well as your physical health. Much like an Olympic athlete 90% of it mental.
It is worth the watch if you are interested in Special Operation Forces training or what they may have gone through for training.