Tuesday, April 23, 2013

VO2 Testing at Seattle Performance Medicine

My training for skiing has changed a tremendous amount in the past few years. After the winter of 2010 my coach and I decided that, while my anaerobic system was quite well-defined and my speed and strength ample for the task, my aerobic system was leaving me lacking in my events. The sprint event in xc skiing is unique in its combination of maximal power demands AND aerobic demands via recovery and often long courses. I would ski well through qualification time trials and perhaps the quarterfinals, but then fall short in ensuing rounds. We decided to put a strong emphasis on aerobic training, and in the last two seasons we've seen huge gains in training markers and overall results.

But still, in this past season I felt something missing in the sprint. I would qualify well, and finish the quarters well but in the semifinals I'd still feel a missing gear. We couldn't determine what the culprit was - aerobic? anaerobic? strength? It's difficult to identify the missing link, and with a training regimen that attempts to cover all these bases we were left at the end of this year scratching our heads for answers. In addition, I've long wrestled with appropriate diet and nutrition - how much is enough? What is my optimal weight/body fat/carb-to-fat ratios? So many questions...

In February when I was bemoaning all these looming questions, Alison recommended that I schedule some metabolic testing at Seattle Performance Medicine, and an evaluation with Dr. Emily Cooper. Alison first heard Dr. Cooper speak several years ago at a running camp, and was impressed with the straight-forward and intuitive information on nutrition for endurance athletes. I hadn't taken a VO2 test in several years (2007 was the last), so I thought at the very least it'd be interesting to see my improvements in capacity.

Metabolic testing can take several forms, but in general it offers much more than that coveted max VO2 figure (point of maximal oxygen uptake). Along the way, a well-conducted test can determine your aerobic and anaerobic thresholds, your percent utilization of carbohydrate, fat, and protein at various intensities, and your metabolic rates during exercise and at rest (how many calories you're burning during the day and during exercise). When combined with expert analysis and summary these data can change your athletic life, for sure.

My last race of Super Tour Finals was the National 50km; I had four full days between that event and my testing, so I made sure to eat lots and rest plenty. You should treat a testing day like a race: you want to be well rested and well-fueled beforehand. The objective is to reach your absolute maximum effort, so any lingering fatigue from workouts, races, or busy living will affect the outcome.

The Seattle Performance Lab is a highly professional, well-run facility. My testing was conducted by Brady Wright, the Exercise Physiologist who manages the testing lab. He got me started with a resting metabolic rate (RMR) test; this one measures how many calories you burn per day just maintaining normal function. It also can show how much of those calories come from fat, carbohydrate, and protein. And all you have to do is lie down and breathe through a mask for 16 minutes! My RMR was 2750 calories, so I need to eat that much plus whatever I burn during daily workouts to keep my body firing on all cylinders. Needless to say, I've been eating probably 50-75% of what I should be, so already I was getting some great data.

Next was the VO2 max test. While protocols vary from test to test, the basic premise is that you run on a treadmill (or cycle, or row, or rollerski) at increasing paces and incline until you can't go anymore. The test is broken into time stages, and the pace and incline are increased after each stage. The whole time, ventilatory data is collected via a face mask and inputted into a computer which graphs it for the physiologist to determine where you're at.

After the max test I did an anaerobic level test, where I ran at increasing speeds on a flat treadmill, again breathing through the mask, until Brady identified via the graphs that I had reached my anaerobic threshold, that point at which my body is demanding more oxygen than I can take in.

After all this data was accumulated and summarized it was time to meet with Dr. Cooper. When we sat down I told her my plight, that I was having trouble finding my top gear in the latter stages of a sprint. Dr. Cooper admittedly didn't know much about the xc ski sprint, but her ample knowledge base of other endurance activities gave her plenty of grounding to identify my weak points. First off, she said, I'm burning WAY too much fat at high intensities. Basically, when you're pushing as hard as you can you want your body sourcing glycogen, which metabolizes much faster into ATP (your body's ultimate energy supply); fat takes much longer. Most sprinters are burning 100% glycogen at their max; I'm burning almost 20% fat! She said that this has probably developed due both to a lack of appropriate caloric intake (especially of carbohydrates), combined with a tremendously strong aerobic system which keeps my body in a more efficient fat-burning state even when I'm asking for quick-fueling glycogen.

The second factor she identified in my search for answers is the close proximity of my anaerobic threshold to my max VO2. Traditionally in endurance sports this is a great thing, as it allows one to go very fast/hard and close to their maximum without going anaerobic and developing a high level of lactate in their system. But for sprinters and power endurance athletes, you need to have room between these two figures, an "anaerobic capacity", which offers you those extra gears. See, lactate is actually a good thing, not only as a secondary fuel but as a marker than you're tapping into your fast-twitch muscle fibers which only burn glycogen (and hence produce lactate). Without that broad anaerobic capacity these fibers don't have much room to run, and your power at high speed/effort is limited.

So how to proceed? First I need to eat more. Lots more. And more carbohydrate. And secondly, I need to back off on my high aerobic training because that system is already too strong for what I need (were I a marathoner, I'd be sitting pretty). I need to put a big emphasis on anaerobic and strength/power training to build that anaerobic capacity under my max VO2. To measure these improvements I'll use lactate monitoring during workouts, to look for high lactates which reflect utilization of fast-twitch fibers.

In all, this testing has provided multiple new avenues for my training, and for the price ($350/session) I consider it well worth my time and money.

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