Hi, Mr. Castro my name is Nadia and recently I wanted to start to run, but I Always start I feel tired, my legs starting to hurt and I can´t finish the 3.1 miles so how can you help me with this little problem? Hi Nadia , when I started to run and do sports I had the same bad problem and I take some time to solve it because I had been doing it wrong but now with me helping you , you will see the difference faster than you imagine. So if you have time to run 3 or 4 times in a week, do it. If you can´t go to the gym because if you create a habit to run you´ll accustom your body for physical activities and will be easier for you. Second, you must forget the distance and time , you should take an watch and say to yourself " today I will run 20 min " and just forget the distance , first we conditioned our body to endurance and after we worry about speed. Nadia I don´t know your physical structure but if you are fat, you mustn´t run because running is an sport with big impact and will hurt your legs and articulations and them look for an sport like swimming or a gym. Bye Nadia I hope had helped you ,thanks for writing.