What Pace Should Runners Run Lactate-Threshold Workouts?

As a coach, I’ve noticed that the most difficult type of workout for runners to run at the correct pace are lactate-threshold workouts. Many runners, especially those who are inexperienced with these workouts, have a difficult time holding back the pace and finding their fastest sustainable aerobic pace. 

Lactate-threshold pace is about 10 to 15 seconds per mile slower than 5K race pace (or about 10K race pace) for slower runners (slower than about 40 minutes for 10K). If using a heart-rate (HR) monitor, the pace is about 75 to 80 percent max HR. For highly trained and elite runners, lactate threshold pace is about 25 to 30 seconds per mile slower than 5K race pace (or about 15 to 20 seconds per mile slower than 10K race pace), and corresponds to about 85 to 90 percent max HR. The pace should feel “comfortably hard.”

It seems that many runners and coaches miss the nuances of the lactate threshold when prescribing training paces for workouts. Every time I read a magazine or mainstream book about running, I read that lactate threshold pace is 25 to 30 seconds per mile slower than 5K race pace, 15 to 20 seconds per mile slower than 10K race pace, and between 10-mile and half marathon race pace. However, these guidelines are only true for very good runners. 

The better a runner’s endurance, the longer he or she can hold his or her lactate-threshold pace, and the better he or she is at sustaining any fraction of his or her lactate-threshold pace. In other words, if a 15-minute 5K runner can run 30 seconds per mile faster than lactate-threshold pace (which equals 110 percent of lactate-threshold pace) for those 15 minutes, certainly a 25-minute 5K runner is not also going to be able to run 30 seconds per mile faster than lactate-threshold pace (which equals 106 percent of lactate-threshold pace) for 25 minutes, 10 minutes (and 66 percent) longer than the good runner. Someone who runs a 10K in 50 minutes is likely running slower than his or her lactate-threshold pace for a 10K, not 20 seconds per mile faster. And someone who runs a half marathon in 1 hour and 45 minutes is certainly not running anywhere near lactate-threshold pace. 

What matters is how long it takes to run the distance, not the distance itself.

Types of Lactate-Threshold Workouts

I typically use four types of lactate-threshold workouts:

• Continuous runs at lactate-threshold pace, starting at about 3 miles (15 to 20 minutes) and increasing up to 7 to 8 miles (about 45 minutes) for marathoners
• Intervals run at lactate-threshold pace with short rest periods, such as 4 x 1 mile at lactate-threshold pace with 1:00 rest or 8 x 1,000 meters at lactate-threshold pace with 1:00 rest
• Shorter intervals run at slightly faster than lactate-threshold pace with very short rest periods, such as 2 sets of 4 x 1,000 meters at 5 to 10 seconds per mile faster than lactate-threshold pace with 45 seconds rest and 2:00 rest between sets
• Medium-long distance runs with a portion run at lactate-threshold pace, such as 12 to 16 miles with the last 2 to 4 miles at lactate-threshold pace or 2 miles + 3 miles at lactate-threshold pace + 6 miles + 3 miles at lactate-threshold pace (I only use these latter workouts for marathoners).

As you progress, increase the training load by spending more time at lactate-threshold pace rather than by running faster. You can do this by increasing the volume of a single workout or by adding a second lactate-threshold workout each week. Only increase the pace of the workouts once your races have shown that you are indeed faster. See the lactate threshold training chart for a sample training program. 

If you want you to perform at the highest level you can, train your lactate threshold—you’ll soon be on your way to achieving new personal records at longer distances.

Sample Lactate Threshold (LT) Training Program

Include a warm-up and cooldown before and after each workout, and fill in the other days of the week with runs to meet mileage goals.

By Jason R. Karp, Ph.D.
For Active.com