A systematic review of research on Tactical Periodization: absence of empirical data, burden of proof, and benefit of doubt

Introduction
Tactical Periodization was developed as an alternative paradigm to periodization. The principles established by its proponents seem theoretically reasonable and well adjusted to competitive sports, especially team sports with year-long competitions, and are quickly becoming popular in sports such as soccer, rugby, and tennis. There are valid arguments in favour of Tactical Periodization, but in science the burden of proof falls on the shoulders of the proponents. Therefore, the aim of this paper was to systematically review articles focusing on Tactical Periodization published in peer-reviewed journals.

Material and methods
The research involved original experimental articles assessing Tactical Periodization in any sport, published in English or Portuguese.

Results
Although Tactical Periodization is an interesting theoretical concept and is currently popular, no empirical research on the subject was found. For that reason, it is premature to scientifically support this periodization model.

Conclusions
The benefit of doubt can be temporarily conceded but Tactical Periodization was created more than 20 years ago. Therefore, it must be properly tested if it aims to be an alternative to current periodized models.