There is no magic system of exercises, sets, and reps.
The authors present two corollaries to rule #9:
- Everything works.
- Nothing works forever.
The warning here is that you should not believe all of the hype about a program. It very well may work (at least for somebody), and it very well may work for you. However, it will not work for you forever, and it may not work for you at all.
There are certainly plenty of hokey systems out there; I can think of numerous commercials telling you that with 20 minutes a day 3 days a week using their machine, you’ll have great abs and bulging biceps. The warning in this rule is that most of the time, the people with those muscles built those muscles doing something else. Take it with a grain of salt.