The Effects of Inter-Limb Asymmetry on Change of Direction Performance: A Systematic Review

Objectives: This review aimed to clarify the associations between COD performance and asymmetries on horizontal jumping, vertical jumping, and strength. Methods: Three databases, including PubMed, Web of Science, and MEDLINE(EBSCOhost) were used to perform a systematic literature search. The search was up to 13 March 2022 and was limited to the literature in the English language and on the human species. Studies included reported exact measurement tools and correlation coefficients and studies in which participants aged >14 years were included. Moreover, studies that were not peer-reviewed and those that did not report an asymmetry index were excluded, as were studies for which the full text was not available. The modified Downs and Black Quality Index tool was used to evaluate the quality of the studies. Results: The systematic literature identified 1151 studies, but only 12 studies were included in this review. A total of 354 participants, ranging from 15 to 23 years of age, were recruited for these studies. The methodological quality score ranged from 6 to 8, with an average of 7.25. The associations between COD performance and vertical jump height, horizontal jump distance, and lower-limb strength asymmetries were examined in 11, 5, and 2 studies, respectively. Six studies reported that vertical jump height asymmetries scores can significantly reduce COD performance, while significant associations between COD performance and horizontal jump distance asymmetries and strength asymmetries were only observed in one study each. Specifically, four studies explored the relationships between CMJ height asymmetries scores and COD performance, and all reported significant associations between them. The main limitations of this review were that it did not consider the sports in which the participants were involved. Conclusions: This study suggests that drop jump height and eccentric knee strength asymmetries can reduce COD performance. Moreover, low horizontal jump asymmetries may not influence COD performance. Further research needs to determine whether the minimal threshold of horizontal jump asymmetries would not affect COD performance.