@Thesexier and then how do you think you will feel about running after TKD practice?? We used to run a mile before class as a group and get right down to it. Try it you will get used to it real quick.
If you are not in runnng shape you should really start with mostly walking, interspersed with short distances where you run. Your wind will likely get stronger faster than your legs. Many people get started running and after getting to the point of being to run for the first mile they feel great and start piling up mileage too fast. This often leads to knee and other problems, probably because the muscles are not ready for it.
My running experience: 30+ years steady plus endurance riding on horseback.
You could run on your off days. I started running just this past December after a 20 year hiatus. I followed a very gentle programme from Kickrunners.com. Basically you interval train 3 times a week until you can run for 30 minutes straight.
I have a compression problem with my anterior tibialis that has impeded my progress, but other than that the programme has been wonderful.
My friend goes to taekwondo in the evening, works out at night, and runs after he works out. Then he long-distance cycles (lance armstrong style) and plays baseball on weekends. And he does all this in between school and work (he already has a bachelors degree after 3 years of schooling). And he’s not tired. lol