How to Find Your Running Speed at Lactate Threshold

Here’s the non-laboratory way to get the data.

low resting heart rate
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There are countless ways to estimate your lactate threshold. Some of them are even accurate and useful, which works out because understanding your lactate threshold could be the key to unlocking running success and breaking through performance plateaus.

Your lactate threshold is the level at which the intensity of exercise causes lactate to accumulate in the blood at a faster rate than it can be removed, making it the border between low- and high-intensity work. You can find your lactate-threshold heart rate to guide your running, or put another way, you can find your running speed at lactate threshold (RSLT).

Various studies have suggested that RSLT is the best indicator of running fitness and the most reliable predictor of endurance performance, so knowing your RSLT can help your training immensely. Once you have determined your RSLT, you can carry out high-quality workouts at specific intensities which are faster than RSLT, which is the best possible way to push your RSLT—and thus your performances—upward.

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How to Estimate Your Lactate Threshold

You could have RSLT measured at an exercise physiology laboratory, of course. You would end up with an extensive printout of your blood lactate readings at various running speeds, and you might even enjoy a chat with an exercise physiologist about what the data points really mean. But, the procedure would be expensive and time consuming, and your test would probably be conducted on a treadmill, with no assurance that your lactate profile would be identical to the one obtained while you were running on something like, say, good old Mother Earth. You would also need to perform the test several times over the course of a season, as your fitness changes, and that means having lots of bucks and—hopefully—living not too far from a hospitable exercise physiology laboratory.

You could utilize one of the commercially available, portable, lactate analyzers, which are pretty accurate and have come down in price to reasonable levels. However, you must prick your finger or ear repeatedly to carry out the threshold test, and you must be a little savvy with your blood-sampling and handling techniques. With all the bloodletting, your mind may not be completely focused on your running (thus giving you a false reading for threshold speed). Don’t forget, too, that when the bloodbath is over you will still have to “fit the curve” (graph your blood lactate levels as a function of running speed). Once your graph looks nice, you also must decide in unerring fashion exactly where lactate threshold is to be found on the upward-curving line. As you can see, there’s plenty of room for error.

More practically, there are also four commonly used field tests for RSLT which don’t involve the loss of even one drop of blood: the VDOT test, the Conconi method, the 3,200-meter time trial, and the 30-minute test. Of these four, research carried out at East Carolina University suggests that the 30-minute test is the best at estimating RSLT, and it is very easy to perform.

To carry it out, warm up thoroughly on a day when you are feeling great, and then gradually accelerate to a tempo which you believe you can sustain for 30 continuous minutes, but not longer. When this tempo is attained, your 30-minute time period begins; during the 30 minutes, you may vary your pace up or down slightly, as necessary, but the idea is to work at your best-possible intensity for the full 30 minutes. The 30-minute field test can be completed on a track or measured course, or with a GPS device.

Once you’re done with the run, estimate your RSLT simply by dividing the distance covered during that time (in meters) by 1,800 seconds (30 minutes). For example, a runner covering 8,000 meters in 30 minutes would have an estimated RSLT of 8,000 meters/1,800 seconds = 4.5 meters per second, for a tempo of 400/4.5 = ~ 89 seconds per 400 meters or just faster than a 6-minute mile.

This 30-minute checkup produces an estimate of RSLT which may seem to be too fast. After all, conventional thinking suggests that RSLT corresponds with average speed during a 15K race, an event which takes all of us longer than 30 minutes to complete. However, bear in mind that the East Carolina researchers measured true RSLT for all of the runners very carefully in the lab (to serve as a reference point for the four field tests). In addition, “The 30-minute test is a workout, not an all-out race preceded by a taper and performed in a competitive setting,” as ECU researcher Joe Houmard points out. It will yield a true RSLT, but the calculated speed will not be as fast as the one achieved during a 30-minute competition.

Once you have your RSLT, your subsequent interval training (to add more lift to your RSLT) is very easy to create. Here are some effective workouts using RSLT pace:

  • 2–4 x 2,000m at two seconds per 400m faster than your estimated RSLT
  • 3–5 x 1,200m or 1,600m at four seconds faster per 400m
  • 6–8 x 800m at eight seconds faster per 400m
  • 10–12 x 400m at 12 seconds faster per 400m

    All of these should have equal-in-time-duration jog or walk recoveries; for example, if you run your 400s in 90 seconds each, jog easily or walk for 90 seconds to recover each time. Alternating these RSLT-enhancing workouts from week to week will add real lift to your lactate threshold, bolster your overall fitness, and carve large chunks of time from your race performances.

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