I just did the same thing two night ago. I started cycling a little over 3 months ago and have been trying to build up my endurance. I have never had good endurance. So I decided I would try running just a bit to see how it went. I only aimed to do a mile and did it at about 9:30. The last time I ran a mile was 11 years ago when I was 18. I was glad I could finish it. The next day the muscles on the sides of my hips were fairly sore as were the muscles on my shins. I also don't own any running shoes so it was completely uncomfortable to run. I do plan on throwing in more running for myself once I have good shoes and probably interchange some walking with my running at first to see how it goes.