Do Non-Circular Chainrings Enhance Cycling Performance? A Systematic Review of Randomized Crossover Trials

Background: Athletes commonly use innovative strategies that aim to enhance their cycling performance. Among them, the effectiveness of non-circular chainrings has been a frequent topic of discussion. This systematic review aims to analyze the physiological and performance effects of using non-circular chainrings in cyclists. Methods: A literature search was conducted on populations ranging from recreational to elite-level athletes, following the PRISMA guidelines. The electronic databases searched were PubMed, Web of Science, Academic Search Complete, Scopus, and SportDiscus, using the search terms ("oval chainring*" OR "non-circular chainring*" OR "elliptical chainring*" OR "asymmetric chainring*" OR "Q-Ring*" OR "eccentric chainring*" OR "chainring*") AND (cycl*), on 11 May 2025. The risk of bias was assessed using the Cochrane Risk of Bias tool with an extension for crossover studies, indicating some concerns regarding the included studies. Results: The initial search identified 291 research articles, which, after applying the screening criteria, resulted in the inclusion of 18 manuscripts. The results suggest that non-circular chainrings do not appear to improve cycling performance metrics or physiological variables during prolonged efforts; however, it is possible that they enhance the sprinting capacity. Conclusions: While the research remains inconclusive, future studies should further explore the effects of non-circular chainrings on sprinting performance.