20min for a 5k cant be very good for an athlete. My cousin and I ran 10k races or bigger most every sunday for years. Fucker was always sub 40 min. Sometimes we watched UFC Then Formula-1 and hung on awoke. Those times, I always felt like shit, wanting to go to bed, but not once failed to complete the distance. We both always smoked a lot. Would smoke cigarettes and weed on our way to the races and even after parking, on our way to the race, we would walk while smoking a last ciggie. After running, always felt wonderful. And hungry. Starving.
We were both lifelong semi-athletes, mostly always training. Ive always been naturally ripped and still drink and smoke regularly.