March 8, 2013 by IowaTriBob
A metabolic assessment helps define your heart rate training zones, establishes your anaerobic threshold rate, and provides an understanding of your VO2 Max. There are several different methods one can use to establish these numbers.
One method is to use one of the numerous (and highly inaccurate) formulas out there to calculate your maximum heart rate such as 220-age or 208-(0.7*age) and then take a percentage of your max. I’ve been guilty of using this method before and found the results to be extremely disappointing. Another way is to perform some self-administered field tests with your heart rate monitor and some perceived level of effort categories. This type of test is somewhat subjective and can change from day to day. The most accurate way is to perform a lab test that specifically measures your heart rate zones, lactic buildup, and thresholds.
I initially found a lab that was able to perform this type of testing looking at the USA Triathlon website for Certified Training and Performance Centers website. In my area I found a lab center, Zoom Performance, at a nearby YMCA. My last visit to Zoom was back in October of 2012 and I was very excited to see what type of improvements the same test would show 5 months later.
Zoom is able to perform Anaerobic Threshold (AT) and VO2 max testing through the use of a breathing mask to measure your levels of CO2. This differs from Lactate Threshold (LT) testing which is performed by taking frequent blood samples. For a more detailed discussion between Anaerobic Threshold (AT) and Lactate Threshold (LT) see wiki.answers.com.
After a short warm-up, strapping on a breathing mask and heart rate monitor, plugging into a lab computer, I was off. The test consisted of starting at a set speed of 5.0 mph (12:00 min/mile pace) and increasing by 0.3 mph every 60 seconds until you can’t continue any more.
Unlike the first time around, I felt great during the entire test and was able to really push myself as I’ve gotten more comfortable with being uncomfortable. The results of the test were surprising. My heart rate zones themselves didn’t really change from the first test. For example, in October my anaerobic threshold was measured at 177 beats per minute. My test this week showed an threshold of 179 beats per minute. Statistically there isn’t any difference between the numbers. So my HR zones continue to stack up as follows:
- Zone 1 (Aerobic recovery zone) – 116-146 beats per minute
- Zone 2 (endurance Aerobic zone) – 146-159 bpm
- Zone 3 (tempo aerobic/anaerobic zone) – 159-168 bpm
- Zone 4 (Anaerobic zone) – 168-179 bpm
- Zone 5 (red line or VO2 Anaerobic zone) – 179+ bpm
Where the improvements really jumped out was at the run pace within each zone. During my first test with Zoom I hit my anaerobic threshold (AT) at a pace of 9:05 min/mile and stopped the test at my max heart rate with a pace of 8:40 min/mile. My anaerobic threshold (AT) pace this time around was an outstanding 7:43 min/mile with a max HR pace of 6:59 min/mile. That’s well over a minute per mile pace improvement. These same improvements continued in all zones with my long run pace dropping almost 2 full minutes from ~12 min/mile down to ~ 10 min/mile. In addition, my VO2 Max improved from 49 to 54 showing a greater aerobic capacity and endurance. All in all – I’m extremely pleased with my progress as shown by the tests and in a relatively short period of time. It’s great to validate some of the time trial testing with actual lab results.
If you haven’t looked into getting metabolic assessment with an Anaerobic Threshold (AT) or Lactate Threshold (LT) test, I’d highly recommend it as it takes the guesswork out of finding your zones and lets you focus on the training itself. It’s also a lot of fun and some great motivation to see your improvements as your training progresses.