When I read your essay, I thought it connected to a video that I had watched recently about how little time we have to do what we want in our life. I think this video will complicate what you began to discuss in your essay. Although there were some nice moments of description, I felt like your run outside was lacking an overarching purpose. For the next draft, I would try to address why running is important to you, what you think about when you are running, and why, with the short amount of time we have in our lives, you choose to run.
The video really emphasizes what little time there is in life, and I think you could connect the idea of purpose and not wasting time to your essay. Was the change from running in the gym to running outside liberating? Is it something you would do again? How does running make you feel? I think really analyzing the purpose behind your running will make it clearer to the reader why you chose to write about running, and how the experience affected you on a personal level.