There's no doubt that training to increase your running velocity at lactate threshold should be included in every runners program but there are often misconceptions about lactic acid and its role in running.
Four misconceptions about lactic acid:
The burning sensation felt in the leg muscles during intense running is caused by lactic acid buildup
The soreness experienced the day after a tough workout is produced from lactic acid
Lactic acid is a waste by-product produced from intense running
Lactic acid only shows up when you run out of oxygen or "go into oxygen debt"
Truth be told, your body consistently produces lactic acid within your muscles and blood even while not running. Something as simple as eating a meal heavy in carbohydrates can raise lactic acid levels significantly. In fact, lactic acid is used as a necessary source of fuel that the liver can use to produce glucose, an athlete's most important source of carbohydrate fuel. Since lactate doesn’t depend on the creation of insulin (unlike pure glucose which does need insulin to convert to fuel your body can use) it represents a quick energy source for your muscles and other organs such as your heart.
Back to running. How can lactic acid become a runner’s best friend? The faster you run, the more lactic acid your body produces. Now that we’ve learned your body can utilize lactic acid as a source of fuel, training your body to pull (or clear) lactate out of the blood and use it for energy is essential.
The best way to increase your body’s ability to clear lactate is assure you’re doing a steady dose of varying high-quality workouts at or just above your lactate threshold. One of the easiest ways to determine your velocity (pace) at lactate threshold without doing a lab test is to use Jack Daniels VDOT chart which uses race times to calculate your velocity at lactate threshold.
Once you’ve determined your lactate threshold pace, run a wide variety of distances at or around that pace. For example, 4 x 1 Mile with 1-minute rest, 4 Miles straight (often called a tempo), 2 x 2 Mile with 2-minute rest, etc. Including these workouts in your training along with workouts stressing your other systems will make you a better runner.