A couple recent studies on plant-based diets and athletic performance:

Plant-Based Diets Benefit Aerobic Performance And Do Not Compromise Strength/Power Performance: A Systematic Review And Meta-Analysis, British Journal of Nutrition, March 2024

Plant-based diets had a moderate but positive effect on aerobic performance and no effect on strength/power performance. … The results indicate that plant-based diets have the potential to exclusively assist aerobic performance.

The Impact Plant-Based Diets Have on Athletic Performance and Body Composition: A Systematic Review, Journal of the American Nutrition Association, 24 June 2024

Plant-based diets may improve maximal oxygen consumption, vertical countermovement jumps, and relative strength.

This one below is a review article but I’m including it here for its lengthy reference list.
Plant-Based Diets for Cardiovascular Safety and Performance in Endurance Sports, Nutrients, January 2019

Conclusions
Plant-based diets play a key role in cardiovascular health, which is critical for endurance athletes. Specifically, these diets improve plasma lipid concentrations, blood pressure, body weight, and blood glucose control, and, as part of a healthful lifestyle, have been shown to reverse atherosclerosis. The possibility that such diets may also contribute to improved performance and accelerated recovery in endurance sports is raised by their effects on blood flow, body composition, antioxidant capacity, systemic inflammation, and glycogen storage. These attributes provide a scientific foundation for the increased use of plant-based diets by endurance athletes.

Technically, plant-based is not the same as vegan. Vegan excludes all animal foods; plant-based may include a minimal amount of animal foods.

Torre Washington, Professional Bodybuilder, Vegan since 1998. Source: his site:

Chris Paul, Professional Basketball Player, Plant-based since 2019. Source: USA Today Sports: