I think there's plenty of things to write for this topic as long as you've been active in sports in high school .
You can mention you active participation in sports and how you've always been passionate about it . You can say how it has developed in you team spirit and has in the process made you a good leader in sports and even in other activities and you have learnt the importance of goal setting, strategizing and planning . Also the obvious stuff like how you're more fit ,healthy and active because of it .Sports also boosts your self esteem and confidence that help you perform better in life .
Well , I think you can elaborate these things and write an impressive essay