Thanks for the chapter :D
There is already some interesting characterization being done here. Chihaya's relapse after the cancelled Nationals is different from her becoming a shut-in during middle school. The first time, she was just be shocked by the collapse of her identity. This time, she's completely unable to do anything because she convinced herself that things will always go wrong; she's afraid to set goals and "give things her all" after she spent her entire high school career training for a race that never happened.
The thing is, she's not exactly wrong. Even though she missed out on everything through being a shut-in, her specializing was what led to her having nothing to show for anything, both in middle school and high school.
On the other hand, Mio clearly faces different issues. I wrote in the last chapter discussion that she clearly has a motivation for running; we won't know her current issues fully until we know why she enjoyed running so much. I suspect she enjoys running because she has to put effort into it; she likely envies Chihaya, who used to run just for the sake of it. Because of the pandemic, Mio probably had to settle for a normal, boring life, where she was never able to "give things her all..."
But that's all speculation, of course.
Anyways, that was another fantastic chapter. I can't wait to see more.