<human>: Could you distill the essence of the text into 1-3 sentences?

Hey guys.

I just finished my first year at uni and, while I am still in shape, I didn't do as much cardio as I would have liked during the school year. I swam in high school, so I used to be pretty good about that. I lifted throughout the year, just didn't run because, well, I didn't really need to.

I started playing ultimate over the summer and I realized I was severely out of shape in that regard. For reference, I used to be able to run a sub 5:45 mile. I don't know if that is good or what, but for a swimmer (and someone who didn't really run much else), I did okay.

Anyways, I'm playing ultimate, getting killed by some fast people, and I want to improve. I do, mostly, want to work on sprinting but I figure I need a good endurance base first. 

The only problem is after playing ultimate my ankles are shot and my shins are pretty sore (the day after). I tried running today and I couldn't at all without there being pain. Is this when you push through it?

Any advice? I can try running a few days after playing but I want to get started running again soon and this bothers me.

Helps appreciated, thanks guys.
<bot>: Play ultimate, get sore. Haven't ran in 6mo. Used to swim. How can I get my endurance back (I have a few ideas on this), any tips on the soreness, etc.