Background: The Yo-Yo test is widely used both in the practical and research contexts; however, its true test-retest reliability remains unclear.

Objective: The present systematic review aims to identify studies that have examined the test-retest reliability of the Yo-Yo test and summarize their results.

Methods: A search of ten databases was performed to find studies that have investigated test-retest reliability of any variant of the Yo-Yo test. The COSMIN checklist was employed to assess the methodological quality of the included studies.

Results: Nineteen studies of excellent or moderate methodological quality were included. When considering all variants of the Yo-Yo test, the included studies reported intra-class correlation coefficients for test-retest reliability ranging from 0.78 to 0.98 where 62% of all intra-class correlation coefficients were higher than 0.90, while 97% of intra-class correlation coefficients were higher than 0.80. The coefficients of variation ranged from 3.7 to 19.0%. Regardless of the variant of the test, the participants' familiarization with the test, and previous sport experience, the intra-class correlation coefficients generally seem high (≥ 0.90) and coefficients of variation low (< 10%).

Conclusions: The results of this review indicate that the Yo-Yo test (in all its variants) generally has good-to-excellent test-retest reliability. The evidence concerning reliability arises from 19 included studies that were of moderate or high methodological quality. Considering that most of the included studies examined the Yo-Yo intermittent recovery level 1 test while including Association Football players, more reliability studies examining Yo-Yo intermittent recovery level 2 test and Yo-Yo intermittent endurance level 1 and level 2 tests, and in the context of sports other than Association Football as well as in non-athletic populations, are required. Finally, future studies should explicitly state the type of intra-class correlation coefficient used for the reliability data analysis to allow for better between-study comparisons.