Lon Kilgore reviews academic literature on periodization from 2000 to 2015 and finds little support for the NSCA’s contention that classical periodization is superior.
Academic evaluation of periodized training has historically been quite limited, and very few experimental papers on the topic were produced before 2000. Attention was firmly affixed to endurance training for heart health as weight training and high-intensity training were not accepted means of improving cardiac health. As a result, very few (less than a dozen) actual experimental papers were produced on periodization of exercise in the latter part of the 20th century. Virtually all Western thought on the topic was rooted in theory, not data.
It’s often difficult to have a coherent discussion regarding periodization because people generally do not get weaker or less fit when they train regularly on a periodized program. That fact provides many people all the ammunition they need to hold up periodization as the gold standard for training.
Conversely, people generally don’t get weaker or less fit when they use a non-periodized program or a program based on a periodization plan different from Leonid Matveyev’s classical variation.
Without comparative data, the argument cannot be settled. Even though periodized programs have lots of anecdotal and some experimental evidence supporting their effectiveness, significant comparative data must be present for someone to definitively say a system of programming—classical periodization, for example—is best. Prior to 2000, there was virtually no such data.