Periodization of training has no scientific validation. There is no research that shows that periodizing your training is of any benefit. According to Carl Foster, Ph. D,. and past president of the American College of Sports Medicin (ACSM), "Periodization is how to mix various types of training to get optimal competitive result at the desired time. There are virtually no controlled data addressing the value of periodization." Additionally, Foster suggests that some of the originators of the periodization training system developed the program to match the cycle of steroid and other performance enhancing drugs to both conceal their use and to give their athletes the stress-strain cycle they needed to maximize their illegal use.
Thanks for your note. There is some truth to the fact that there is very little in the way of research to support periodization. But the few studies that have been done generally support it. This is kind of like saying there is no research proving that breathing helps performance. That would also be true but doesn’t mean you shouldn’t breathe while exercising.
Periodization has its roots in the early 1900s before steroids and other performance-enhancing drugs were known of.