We want to get you in the habit gradually. If you're starting from scratch, starting at two or three days a week is a good starting point. Maybe start at about 20, 30 minutes at a time, not running the whole time but with a walk-run combination. If you're taking 20 minutes, maybe walk for about four to five minutes, run for one. Do that about four to five times until you've worked up to your 20 to 30 minutes. If you're going to start with 20 minutes, do a combination of four minutes walking, one minute running and do that four times. You've got 20 minutes. If you do that two or three times a week, you'll help to allow your body to gradually adapt to it.
Each time you start a new training program, you want to allow your body about four to six weeks to adapt to that new training stress. With a new training program, you might feel a little soreness. This is expected and it will go away. But if it doesn't, take a couple days off, let your body rest, and try to get back onto your running schedule. Each week as you start to feel more and more adapted to your program, decrease the amount of time that you're walking and increase your running. So maybe about three to four weeks in, now you're walking about three minutes, maybe four, and you're running about two minutes at a time. And again, try to stick to 20 to 30 minutes.
In order to get some variety in your training program, take a rest week. Cut down the time that you're out running and walking. Maybe cut down a day. So as you continue building, you'll gradually cut out all that walking and you'll be running consistently and on your way to your new running schedule.