I started running a couple of weeks ago and it's super fun. The past couple of years i've run a couple of times a month and done weight lifting for muscle mass. This has been fine.
Since i started running 10K's 2 times a week (and stopped drinking when i'm out partying) i've started to become more competitive with myself in regards to the time and recently did my first sub 45 min 10k.
As this might indicate i'm not a pro athlete which also leads me to my question. After the first 5k i feel like i can't feel my heartbeat because it's beating so fast and my lungs sort of start breathing on their own without me controlling it. It's also at this point my legs start to feel kind of sore like if they weren't getting enough oxygen. I never had this feeling when i just ran 3K in a jogging tempo and i kind of scares me since this is a fairly new level of running to me. Is this normal?
After the run i have to catch my breath for 2 minutes and then i'm back to normal.