Start doing some interval work.
Instead of running four laps around your block, run one lap, which would be about 400 meters.But, run this lap at a faster pace than your regular 4-lap run.You are only going a quarter of your normal distance so you should be able to put more effort into the single lap.Now rest between 60-90 seconds and repeat the single lap.
Try doing these intervals 3 non-consecutive days per week, say Monday, Wednesday, and Friday.Keep on eye on your volume.Try to GRADUALLY increase the number of intervals you run.Shoot for a goal of 12 laps @ 400 meters each at a pace that is between a fast run and an all-out sprint.Use a 60 second rest interval between each lap.A good time if you are clocking yourself is between 60-75 seconds per 400 meters.
Interval training is all about quality, so keep things intense but watch your recovery.I was able to drop 22 pounds and get into great shape for amateur boxing in three months by following a similar program to the one outlined above.It works.