Miler to marathoner, and all runners in-between

Training like a miler makes you a better runner in general, at least according to this article. First off, how do milers train? Well, they do shorter repeats (200-400m) at their 1500-3000m pace (~15-40sec per mile faster than your 5k pace). The entire workout might only total 1-3 miles in length, but the pace is quicker than what many of us are used to (there are some example workouts on page 3 of the article). So, why is this beneficial? Well, these shorter repeats  result in a faster accumulation of lactic acid. Training at this level helps you to tolerate higher levels of lactic acid by improving buffering capacity. Additionally, faster repeats puts more stress on your heart, causing it to pump harder. Over time, your heart becomes stronger, resulting in an increased stroke volume with each beat (which results in a greater cardiac output). Aside from these physiological benefits, running fast improves leg strength and neuromuscular recruitment, which makes you a more efficient runner. Just make sure that you're warmed up before starting the workout, and be sure to stretch out afterwards!

Note: the only distance that this type of training produces no benefits for is the 5K Marathon... mainly because it is a FICTITIOUS DISTANCE (what the heck LiveStrong?!?)