Lactate Threshold 101: How to Find Yours

On the Treadmill
Finding your Lactate Threshold can be as simple as running on a treadmill if you’re okay with just an estimate.

We introduced you to Lactate Threshold, so you should be all fired up to find your very own LT and add it to your endurance arsenal!

Currently, there are 3 ways to determine your Lactate Threshold. The first requires sweat and math, the second requires sweat and blood, and the third requires three hundred bucks. UGH! Hang with me! You’ll be glad you did.

Find your Lactate threshold after the jump!

Option #1: Field Test

The needle-free option for determining your LT is to complete a 30-minute field test.

  • YOU WILL NEED:
    • A traffic-and-stoplight-free circuit to run for 30 minutes. You will want to know your distance in meters, so a treadmill or track is ideal.
    • EITHER: a GPS device and a heart rate monitor, OR a stopwatch and a REALLY good run-by-feel instinct.
  • PROS: It costs nothing! You can do it by yourself or with a friend whenever you want.
  • CONS: It’s only an estimation of your LT and, if you don’t train with a heart rate monitor, the results depend very much on your own perception of how you feel.
    • For example, if Runner #1 has a high pain/suffering tolerance and can push themselves harder during the test than Runner #2, who keeps their pace down to maintain comfort, they are going to get different results even if their LT is technically the same.

How to do it: Pick a day when you feel fresh and find a course without distractions. You don’t want to be forced to stop at any point during this test. Warm up slowly, increasing your pace until you reach the fastest tempo you think you can sustain for 30 minutes (this is not a jog, folks! This is a time trial, a mock race!) then start your watch. Run as far as you can in 30 minutes. The trick is to run as FAR, not as FAST, as you can. You can’t jump off the starting line and run ALL OUT because … well … who the heck can sustain a full-out sprint for 30 minutes? Pick a pace that you can sustain fairly consistently from start to finish. It’ll skew your results if you start at a 7:30 pace, burn out halfway through, and finish the test walking.

If you train using a heart rate monitor, your average HR for the last 10 minutes of the time trial is your estimated LT heart rate. If you don’t train with a monitor or GPS, simply divide the distance you covered (in meters) by 1,800 seconds (30 minutes).

For example, if you cover 6,000 meters in 30 minutes, you would have an estimated LT pace of 6,000 meters/1,800 seconds, or 3.3 meters per second. Divide one lap around the track by that pace to get 400m/3.33s, which equals about 120 seconds per lap. Multiply by 4 (4 laps = 1 mile) and that’s about 480 seconds for a mile, which translates into an 8-minute mile for your Lactate Threshold training pace (480 ÷ 60s = 8 minutes). TA-DA!

You can read a similar description of 2 different field tests here, for additional ideas and clarity.

Option #2: Lab Test

  • You will need:  1) Access to a sports medicine/performance clinic, 2) Some extra cash laying around, 3) To feel comfortable being watched (and stuck with a needle!) while you run on a treadmill.
  • PROS: More accurate
  • CONS: Getting stuck with a needle, costly

To get a more exact Lactate Threshold, you have to see a professional. One of the downsides of a professional LT test is that it can cost $125 or more. This test requires you to wear a heart rate monitor, to run on a treadmill in a lab for 20-30 minutes, and to have your finger pricked a whole bunch for blood samples.

Last fall I was recruited to help a company test a new running product. The product developers wanted to use groups of runners to test the new gadget and get valuable data. In exchange, runners got a free LT test and a nice printout of LT training zones to use for workouts. I’m not fingerprick-phobic, so I signed right up!

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A lactic acid spike during LT testing (www.trainbsx.com)

I got to the lab, filled out some paperwork and stretched. The lab techs hooked me up to a heart rate monitor. The techs explained that they were going to have me warm up and then start to increase the pace of the treadmill every few minutes after that. They would also take a finger-prick blood sample every time the pace changed so they could see what the lactic acid in my body was doing along the way.

Run, finger prick, increase speed…run, finger prick, increase speed … over and over again. The techs entered my blood samples into a computer that showed them exactly how much lactic acid I was producing. As expected, my reading stayed very low/steady in the early stages because my body was processing fats and carbohydrates efficiently.

The magic moment came about 30 minutes into the test when my body decided it was leaving the “endurance” zone and moving into the “can’t…sustain…much…longer!” zone. This was picked up in the final finger prick reading, when the techs saw a sharp spike in my lactic acid reading. The test was over as soon as that spike came, and it was determined that the pace I was running just before it happened was my Lactate Threshold. It was a cool experience, of course, and interesting information, but kind of a pain. Plus I’d need to go back and pay to get re-tested every time my fitness changed or improved.

Option #3: The Gadget

  • You will need:  $299
The BSX Insight (www.trainbsx.com)
The BSX Insight 

That new little gadget I mentioned above is a first-of-its-kind device built to measure Lactate Threshold through your skin. The BSX Insight is a non-invasive device that pairs with your sports watch and “looks inside” your muscles to determine how hard they’re working during exercise. It can be used for running, cycling, or swimming. No needles, no labs, no field-test guesswork.

BSX claims it can measure the lactic acid in your body without all that. You pop the Insight into a calf sleeve and voila! Real-time information about whether or not you should speed up, slow down or rest, depending on what kind of workout you’re trying to do.

It also analyzes your heart rate and your cadence at the same time. Not only does this make professional-level Lactate Threshold test results completely accessible and way less expensive over the long haul, it also opens up a world of training possibilities for athletes of all abilities. The techniques and data that elites have used for years are finally trickling down to us mere mortals, and I am pretty excited about that. It’s like having a sports medicine lab and a top-notch running coach attached to your leg!

I don’t have any relationship with BSX other than being their guinea pig during the Insight’s early test phase, so there’s no conflict of interest here. They haven’t given me or Salty Running any free stuff (except that first LT test) and haven’t asked me to shout the Insight’s praises, but that’s exactly what I’m doing! It truly is an exciting breakthrough in running technology, and I’m thrilled that we’re taking such amazing strides (ha!) into the future.

Also check out: A nifty workout to use your newly-acquired Lactate Threshold knowledge!

Have you ever completed a Lactate Threshold test? At $299 for the runner’s edition, would you ever consider buying a gadget like the Insight?

I'm a nomadic runner who loves moving from city to city with my husband and Great Dane. I write about training with a Type-B personality, battling bad running habits, and becoming comfortable with sub-3 marathon racing despite my race-phobia. After a soul-searching year away from running, I'm thrilled and terrified (thrillified?) to be making a major comeback in 2018!

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5 comments

  1. This is interesting. I’m curious, for those of us who might want to ballpark it even more, how closely does LT line up with half marathon pace? Sometimes I’ve seen LT and half marathon pace used almost interchangeably — e.g., Pfitzinger’s Advanced Marathoning suggests doing lactate threshold runs at half marathon to 15k pace. Just wondering if this aligns with your experience — i.e., how close was the result from your lab test to your half marathon race pace?

    1. Good question! For me, it kind of depends on the time of year. When my marathon training season kicks off in the fall — ie: after a looooong summer of slacking off — my LT workouts are shorter and my pace is usually closer to my “in-shape” half marathon pace (6:30-6:40) for a couple weeks. (*Disclaimer: I’ve only ever done 2 half marathons, so I don’t have a ton of data to go off here…marathons are more my thing.) As the season progresses, the weather cools off, and I get back into shape, my LT pace tends to drop down to around 6:20 and ends up being faster than my half pace. From what I’ve read, I think LT pace SHOULD be a touch faster than half marathon pace for most folks. 15k pace is probably even closer to the LT mark, but I think either one could be a great ballpark/starting point for LT workouts.

      1. Forgot to mention…it’s good to remember that LT will absolutely change as your fitness changes. When I did that LT lab test in the fall of 2013, my marathon PR was right around 3:25 and my half was barely sub-1:40, so my LT pace was nearly a minute slower than the LT pace I shoot for now that I’ve brought my marathon PR down to 2:59. It’s a moving target from season to season and, like I said, sometimes it can even vary within a season. Worth the effort and the attention, though. LT workouts have been a game-changer for me! :)

  2. I’d love to have one, but $250 is way too expensive for me (unless I win the lottery, which is in my long-range plan).

  3. That BSX Insight device looks interesting! It’s amazing how new technology can help us with training. If the price is ever reasonable, I might consider buying one in the kind of far future (when I can actually afford it). I don’t even have a HRM!