Interval training is a way of doing cardio that will give you the ability to make gains in time and distance much more easily than any other method. The principle of interval training is that you push yourself really hard and then you slow down.
This repetitive form of training leads to your body needing to adapt to changes and this is really great for you. The body begins to build new capillaries, and is better able to take in and deliver oxygen to the working muscles. Muscles develop a higher tolerance to the build-up of lactate, and the heart muscle is strengthened. These changes result in improved performance particularly within the cardiovascular system.
When people begin running they automatically do interval training where they will alternate walking and running to get a better workout in. As people get better at running they will start just running and not stopping until the 30 or 60 minute run is over. The upside of this is that you will get a much better workout and feel fantastically exhausted at the end, the downside of interval training is that you are going to be pushing your comfort zone so the workout itself is going to be painful
So how can you implement interval training into your regular workouts? I have a few examples. When you begin running as I said before you are going to have trouble running for any length of time so you decide that you are going for 20 minutes and you will do cycles of jogging for 30 seconds and then walking for 30 seconds. As you get better at running you will be able to jog for one minute and then walk for 30 seconds. You will notice that your rest stays the same but the running time increases until you get to the point that you do not need a rest for your 30 minute run.
As an advanced runner you are not going to slow down for a walk but instead your will run for 5 minutes and then break into a spring for 30 seconds or a minute and then slow back down to your regular pace. As another way to do interval training you can go to another location that is more hilly and use the uphills to change up your pace. The hills are going to force you push harder to keep the same pace and of course the downhills are going to use different muscles but as far as exertion goes you will find the running easier.
Try interval training soon either indoors on a treadmill or outdoors as long as the weather cooperates.