Lactate Threshold a Key to Faster Times

Plus how to improve yours

British Olympian Sebastian Coe once famously said, “I’ve always felt that long, slow distance produces long, slow runners.” Indeed, many runners are intimidated by harder, high-intensity workouts, opting to put in mile after mile at an easy pace instead. But these are also the runners who struggle to get faster.

If you’ve been stuck in a routine rut—or are just hoping to take your PR from good to great—it’s time to focus on your lactate threshold (LT) pace, one of the best, oft-neglected predictors of running performance.

What is a lactate threshold, anyway?
Think of it this way: When you run, your body produces lactate—a by-product of the glucose that your body breaks down for energy. As you increase your speed and distance, the body eventually hits a tipping point wherein it can’t effectively utilize the lactate for energy. And that’s the awful moment when lactic acid begins to build up in your bloodstream, your muscle contractions become weaker and, ultimately, you slow down. Behold, your lactate threshold (also known as your anaerobic threshold). The higher your LT, the better distance runner you’ll be.  

How do I find mine?
To determine your personal LT pace, you could fork over the cash to go to a lab or buy a lactate analyzer—but a good old-fashioned time trial with a heart rate monitor will also give you similar results. Begin by warming up. Then, on a track or using a GPS, run the fastest pace you can sustain for 30 minutes. (Try to keep the pace fairly even, so you’re running at your best effort for that half hour.) Your average heart rate during those final, leg-burning 10 minutes of the trial is your LT heart rate—the guideline to use for future LT workouts.

OK, found it. Can I improve it?
Luckily, unlike your VO2 max, which is relatively preset, you can improve your lactate threshold with training. By running slightly under that determined pace, your body learns to deal with the increase in lactic acid more effectively—which, practically, means that a faster pace actually feels easier.

That sounds great. How do I do it?
Begin by adding one lactate threshold workout a week to your routine. If this means that you lose some mileage, don’t freak out: In new research published in The Journal of Strength and Conditioning, runners who ran fewer miles (31 in the study) at higher intensities improved their VO2 max velocity and lactate threshold more than runners who put in additional mileage (43 miles) at a lower intensity.

Interval training and tempo runs are two staple LT workouts. For an interval workout, try beginning with 4x1600m intervals run at just below LT pace with equal recovery between each—and over the course of several months, increase the speed and number of your intervals. For a tempo run, begin with a short warm-up. Then, hold your LT pace for 20 minutes straight. As you get stronger, increase the length of these workouts.

Use your LT heart rate as a guide to your pace. If you’re still nailing that down, it may also help to think of your pace as the fastest speed you can muster for 30 to 60 minutes (though the more fit you are, the longer you should be able to hold it). It’s not a sprint, but it's not a jog, either.

Sure, it will hurt at first. But many runners actually enjoy these high-intensity training days—not only will they ratchet up your speed, but they inject a little challenge and variety into a running routine. So what are you waiting for?