Yesterday I had a full metabolic assessment performed to calculate my body's profile for converting oxygen, fat, and carbs into energy. Frankly I didn't really know what this meant when I signed up, but it seemed like it would provide some really interesting data (and it is well documented how much I drool over data!) with which to fine tune my training and racing.
The specific assessment product to be used is called New Leaf, which I discovered at DC Rainmaker's fitness equipment blog. At the New Leaf website, I learned that the closest New Leaf site is in Pasadena (TX) at Third Coast Training. I would have to break my usual rule of not leaving the safety and comfort of Houston's inner loop, but it would be worth it.
The New Leaf assessment required 12 hours of fasting beforehand so I scheduled mine in the morning. At 7:45 I arrived at Third Coast Training and met Johnny Shelby, the owner and former world class middle distance runner for the US Army's track team. I was immediately relieved to find that Johnny is extremely knowledgeable, not just some yokel spouting off sound bites that he learned during a weekend training course.
The first test of the assessment measured my resting metabolic rate (RMR). This is the number of calories I would burn if I were to lie around in bed all day. There are various methods for estimating this number and most predict (based on my height, weight, gender, and age) that my RMR should be 2,000-2,200 calories per day. Instead of estimating, though, now we were going to know for sure.
The test required me to lie down with a "gas mask" attached to my face. I felt kind of like I had an alien from the "Alien" movie series stuck on my face - which didn't help me to relax! The mask measures the oxygen and CO2 content of each exhalation, which it uses to calculate to total number of calories your body has expended. This test lasted 15-20 minutes and the greatest challenge was staying awake the whole time.
RESULTS: it turns out that my metabolism is really sluggish - with an RMR of only 1,600 per day! I don't know why it would be so slow, especially given my high amount of muscle mass, which is ostensibly a metabolic furnace! My theory is that I have undernourished on some of my really active days (e.g. volleyball tournaments), which has left me with a caloric deficit of 1,000+ calories. Perhaps my body reacted to those instances by really slowing down my metabolism. Or maybe I just have a genetically very slow metabolism. Regardless, I want to boost this number so I will work at ensuring adequate nutrition especially on "big" days.
The next test was my full metabolic profile. This also involved wearing the "gas mask" but this time on a treadmill (at a 2.0% incline to simulate outdoor running better) instead of lying down. We started at 5.0 mph for three minutes. At the end of three minutes, Johnny pricked my finger and took a blood sample, which was used to measure my lactate levels. Taking a blood sample while someone is running is a tricky business but Johnny was a pro and it went off without a hitch. Without stopping my speed then went up by 0.5 mph and we continued like this in 3-minute stages; I was told to tap out when I felt that my legs were too fatigued or that I was too out of breath to continue.
This went on for awhile until, at 9.0 mph, I finally tapped out. It turns out that I am basically a big sissy and I probably could have gone up two more stages based on where my lactate levels were when I quit. This is a big blow to someone who prides himself on mental toughness! When I tapped out I didn't know what my heart rate was or how much time was left until the next stage. I hadn't eaten for 13 hours, I was wearing a crazy new gas mask, and my finger was being pricked for blood every three minutes - all of this was new/unsual to me. When there is uncertainty in my running, I become anxious. But, like any good nerd, when I have data, I stay calm and I have the confidence to push through. When I know how much longer I have to go, I can dig down and pull it out; when I don't know, though, my natural inclination is to give up. This seems like a big weakness to me, especially when one thinks about the implications outside of the running world--in business, for example. So I will work on it but, in the meantime, I will also make sure to avoid "running blind" in critical situations.
RESULTS: I was pleased that my metabolic profile and lactate levels showed pretty strong signs of fitness, my processing of oxygen actually increasing in efficiency as exercise intensity increased. Through 6.5 mph my body stayed in an aerobic zone, heart rate under 160 BPM, lactate levels under 2.0 mMol, and VO2 in the 32-38 ml/kg/min range. Through 7.5 mph my body began using more glycogen as a fuel source, heart rate under 170 BPM, lactate levels up to 3.53 mMol, and VO2 in the 38-46 ml/kg/min range. While running at 8.0 mph my body crossed the 4.0 mMol lactate threshold, reached 177 BPM, and VO2 pushed up to 50+ ml/kg/min. At 8.5 mph, the last full segment I completed, lactate levels spiked to 7.55 mMol, heart rate reached 184 BPM, and VO2 reached 53 ml/kg/min. According to Johnny I probably could have continued for two more segments, reaching a lactate saturation of ~12 mMol and a VO2 max of maybe 56 ml/kg/min.
This shows that my aerobic fitness is "pretty good" but shows plenty of room for improvement. Similarly my anaerobic performance has plenty of upward room - good! Johnny worked out 5 heart rate training zones for me and they differed considerably from the "standard" zones provided by estimations or my Garmin ForeRunner. The first zone is my aerobic "base," where I operate at peak aerobic efficiency. Zones 2 and 3 are more of a mix between oxygen and glycogen energy systems. Zone 4 is above my anaerobic threshold so is basically my Lactic Acid system. Zone 5 is unsustainable peak exertion, my ATP-PC system.
My goal is to push up my aerobic base while simultaneously increasing my my anaerobic speed and duration. This will be accomplished by mixing in 100% Zone 1 jogs with interval runs that alternate between the peak of Zone 4 and Zone 1 for recovery. I have been running too hard in recent months to do anything beneficial for my aerobic system and it is so hard for someone like me to accept that you can slow down in order ultimately to run faster but I'm going to give it a try. By not running hard all the time hopefully I will be less prone to injury/exhaustion too. Also the New Leaf website makes it easy to upload your heart rate zones and true metabolic calorie burn rates to your Garmin ForeRunner, which is really convenient.
Of course I'll be submitting all of these results to The SHOP for their interpretation of the results and training ideas as well. I will post updates on progress but, in the meantime, I highly recommend the New Leaf product and, specifically, Third Coast Training, to those interested in an analytical approach to energy system training.