GMU S.M.A.R.T. Lab Body Compisition and VO2 Max Testing

For my 32nd birthday my wife got me a session at my local university's Sports Medicine Assessment Research & Testing Lab, aka SMART Lab.  My particular session included a Body Composition Analysis (i.e., body fat analysis) and a VO2 Max test.  They also offer a 3D gait analysis, but that was not part of my trip today.

I think my wife got me the Body Composition analysis to finally prove to me that I am too skinny.  She pretty regularly tells me I could stand to gain a few pounds.  I respond by eating excessive amounts of popcorn, but it doesn't seem to do the trick.  Apparently all that training cancels out all that popcorn.

The Lab is apparently only open in the middle of the week, which means I had to treat this like a doctor's appointment and excuse myself from work.  Finding a time that worked was difficult due to my schedule and the ebbs and flows of my job - the slots were actually very consistently available which made me think that the service is not widely utilized.

The Lab is housed at George Mason University's Freedom Aquatics and Fitness Center, which is contains a huge pool and tons of fitness equipment and studios.  It's open to students, of course, but also the general public.  The Lab is on the second floor in an administrative office area of the gym.

I got there and the appointment before mine went a bit long so I got to prepare myself mentally for what I was sure would be a physically exhausting endeavor.  Of course, before the VO2 test was the BodPod.  It's a small chamber that uses air displacement and plethysmography to measure your body fat and is within 1% body fat of DXA, which is the current gold standard.

I stripped down to some spandex underwear and put on a swim cap.  The tech calibrated the BodPod, measuring it empty and then with a known volume in it.  I stepped on a scale to get my weight at that exact moment, and then stepped in the BodPod, which measured how much air I displaced.  The experience itself was fine.  Although the chamber was small, there was a large glass viewing area which lessened any feelings of claustrophobia.  What I wasn't expecting was to feel the pressure changes in my ears.  In reading about how the measurements are taken, it makes sense as there are speakers that vibrate the air (which is what I was feeling in my ears), and those vibrations are measured.  Because of the act of breathing, two measurements were taken and averaged out.  With my weight, height, and displaced volume, my density was derived.  Then my density was plugged into a magic formula and my body fat percentage came out, along with my fat mass.  I got a really neat print out that has my height, weight, body fat percentage and how much fat I have on me.

In case you were wondering, I'm 5'9.6", 149.5 lbs and have 10.3% body fat.  The handy little reference chart they gave me tells me that I am on the line between ideal and lean for my age.

After that it was time for the VO2 Max test.  I have done some lactate threshold testing with my BSX Insight, so I felt like I had a good idea of what I was in for.  The protocol is pretty straightforward - warm up and get a baseline pace and readings, then once the test starts proper, keep the pace constant, but increase the incline by 2% every other minute.  In my LT tests that I've self administered, the incline is kept consistent, but the pace increases.  I don't have hills in my training plan and the ones I face naturally are definitely of the sneeze-worthy variety.

Because it doesn't count if it wasn't on Strava, I had my 920XT, HRM, footpod, and BSX ready to go to capture every aspect that I could about this adventure.  I thought it would be especially cool to compare the SmO2 data from the BSX to the VO2 data from the test.  Unfortunately, that wasn't to be, for some reason the BSX crapped out after 5 minutes, which was about 30 minutes before the test actually started.  It required a hard reset which requires a strong magnet to do, so I just had to go without.

Getting set up for the test was pretty time consuming, aside from getting the mask fitted and finding a heart rate monitor that worked (though I had my own, they apparently need one that uses Polar's proprietary fitness equipment protocol), there was a lot that the tech had to do on his end to get everything dialed in.

As I mentioned, I've done LT tests on my own before, and they normally last about 35 minutes before I give up, topping out at around a 5:30 min/mile pace.  So the expectation I had was that this test would also last about that long.

I did my warm up and decided that I'd do an 8 min/mile pace.  For this test, your actual speed and incline doesn't matter so much as your continually increasing exertion.  The point being you need to find how hard your body works and how well it's able to respond to stress.  The VO2 number itself is the rate in milliliters per kg per minute of oxygen consumed.  The VO2 max is reached when oxygen consumption remains at a steady state despite an increase in workload.  The idea is that the more oxygen consumed, the more aerobically fit you are, and this makes sense - if your body can continue to make use of more oxygen as you increase workload, you're going to be able to adequately perform without degradation.  However, once you hit the point where your oxygen consumption remains constant, any increase in workload is going to tax your system and start being anaerobic.  Knowing your VO2 max is a great tool to base training on because the bulk of training should be done in the aerobic zone and this test can help you understand what that is.

My warm up lasted a bit more than 5 minutes.  My heart rate was exactly where I'd expect it at that effort and that point in the exercise, which was about 130.  The incline was boosted to 2% to start the actual test and at the end of the first segment, my HR was up to about 140, then they added 2% and my HR not-so-slowly ramped up to 150 at the end of that segment.  2% more and I was at 165 - already out of my aerobic zone.  At the end of the 8% segment I was at 174.  This was only 8 minutes into the test, mind you and much more effort than the LT tests I had performed.  When the incline was upped to 10% I felt like I was in a bit of trouble.  I made it through that segment with a HR around 180.  The tech increased the incline to 12% but I called it quits at that point.

Throughout the entire test, my HR maxed out at 180 via the chest strap they gave me.  The optical HRM I was wearing clocked me in at 184, which I believe is my true max.  The tech gave me a nice print out of my results with some pretty charts.  It had my VO2 Max, Max HR, HR at Ventilatory Threshold and % of VO2 Max at Ventilatory Threshold.  So a quick primer - Ventilatory Threshold is the point at which your body needs more oxygen than it can consume.  Basically, the point at which you switch from aerobic exercise to anaerobic.  This is the key data point that I wanted to get out of this test, and also what I wanted to compare to the BSX Insight results I've gotten to date as a validation.

Unfortunately, the results I got were bunk.  It put my VT HR at 130.  I've been training with the assumption that it's 158, so that is a huge difference.  Because of how much I run, I know that, while 158 might not be an exact value for when I hit the anaerobic threshold, I know it's very close to it, and if I keep my heart rate there, I could run all day.  I think if I was trying to stay at 130, well first I'd be running about a 9 min/mile pace, and I'd only be able to keep it up for about five minutes or so because I'd get so uninterested due to the lack of challenge that presents to me.

The tech went back to the data and saw that the algorithm used may have misinterpreted the data, so he went and eyeballed the point where he felt the change occurred in the graph and put that down as my HR, which he chose to be 163.  Much closer to what I was expecting, but I still feel a bit uneasy about relying on a number that was eyeballed.  I saw the raw data up on the computer and asked the tech if he could send that to me, since I felt like that would be much more valuable than an arbitrarily chosen number.  So now I have that raw data, but of course, I have less ability than the tech to figure out what the point of inflection is where I go anaerobic.  But, it is very cool seeing how much oxygen I'm consuming at different heart rates.  I figure I'll do a bit of research and see if I can't find some way to mathematically derive the point where my body starts changing fuel sources.

And while less valuable, I'm also a bit speculous of the VO2 max value given to me.  The test clocked me in at 70.12, which for my age literally puts me off the chart (the one given to me with my results tops out at 54.1).  I feel like based on my rankings in some recent races that I may not actually be at 70.12.  Also, I looked at an online calculator for predicted race times based on VO2 max, and it said that with a VO2 max of 70.12, the 10k I just PR'd in with a 39:10 time was actually nine minutes slower than what I was actually capable of.  I might not have run the perfect race, but no way was I nine minutes off.

In a couple of days I am going to re-do my BSX LT test to see if I can't corroborate some of my findings today.

All-in-all it was a neat experience and really cool birthday gift.  I'm looking forward to starting my legit training plan using the details from the assessment, and maybe even eating a bit more food around the holidays to make my wife happy.


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