January 9, 2023
I slowed down and tried the Lactate Threshold Test 2 more times in the past few weeks. I still haven’t been completely successful at completing the test and determining the heartrate that is my lactate threshold with real precision, but I am getting closer. As I wrote in my previous post, determining one’s lactate threshold is important as it is the divide between a pace that is sustainable for up to an hour and one that is sustainable for a much shorter period of time.
The Uphill Athlete offers a test where one runs at their comfortably hard maximum sustainable pace for at least 30 minutes. In doing this the goal is to have your heartrate settle into a tight range. The average of this range is your lactate threshold.
This issue in completing this test is in defining the maximum pace that is comfortably hard. I have done all 3 tests on a treadmill set flat. In my first test, I set my pace at 8:49/mile, but my heartrate never stabilized for long. On my second try I slowed my pace to 9:05/mile, and I had better luck. My heartrate stabilized in 145-146 beats per minute for about 16 minutes before it started climbing. On my third try I slowed my starting pace again to 9:22/mile. My heartrate stabilized in the 145-148 range for a full 40 minutes, but to keep my heartrate in check I slowed my pace with each passing mile. That’s a no no for this test, as one is supposed to maintain a constant pace throughout the test.
So I need to slow down further and complete a Take 4. All of this effort is causing me to evolve my sense of what maximum pace that is comfortably hard means. It’s not just a pace that you can stick to for a half hour or more, but it’s a pace that you can stick to while keeping cardiac drift from setting in. My best assessment right now is that my lactate threshold is somewhere between 143 and 148, so I set it at 143 on my Garmin. The range of that assessment will hopefully tighten after the next test.
Before starting Take 3 of my Lactate Threshold Test, I also did my first take of an Aerobic Threshold Test. This test is used to find the boundary between Zone 2, where you are burning more fat than carbs, and Zone 3 where the reverse is true; fit runners can hold a Zone 2 pace for hours, but can only hold a Zone 3 pace for about an hour. Formal testing to ascertain your aerobic threshold is available. This testing involves running on a treadmill while your lactate blood levels are monitored. But there is a less formal test suggested in many of the articles I have read on this topic. If a runner breathes through their nose while their heartrate increases, they will reach a point where they have to gulp air. The heartrate where a gulp of air is necessitated is your aerobic threshold.
My experience tells me that this test is best done on a treadmill set flat, as running hills can necessitate the occasional air gulp well below your aerobic threshold. And, since the aerobic threshold is below the lactate threshold, it made sense to me to test for my aerobic threshold after the warmup phase of my lactate threshold test, while I slowly increased my pace and heartrate. More specifically, I incremented the pace by 0.2 mph every minute while breathing through my nose and monitoring my heartrate. I found that I could breathe easily through my nose while my heartrate was in the mid-120s. In the upper 120s, I was starting to feel stressed, but I was still able to suppress air gulps. My stress increased as my heartrate moved into the 130s, though I still was able to suppress any gulps into the low 130s. Once I reached 134, I gulped in air.
This test indicates that my aerobic threshold might be as high as 134, but I plan to do this test a few more times before I push Zone 2 that high on my Garmin. After this test, I set the top of Zone 2 to 128. I’d rather be on the conservative side in setting zone boundaries. If Zone 2 is set too low it just means that I am still burning more fats than carbs in the lower portion of Zone 3. In this first capacity building phase, I think that makes sense.
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