One of the big challenges faced by endurance athletes is estimating fueling requirements for long races. It's difficult to eat during intense exercise, and eating too much can have disastrous results. Eating too little will leave an athlete under-fueled during later portions of their race, which can lead to poor times or dropping out of the race. To help with this dilemma, endurance athletes train their bodies to consume fat more efficiently. The more fat we burn, the less carbohydrate we need to rely on. The problem, though, is that we need to gain a sense of how much fat we burn at various intensities in order to understand how we should fuel when we race. To answer this question, I turned to Spartan Performance for a VO2 max test.
Although finding the facility was a bit of a challenge, I need to note that Connie, Tyler, and Dr. Eisenmann were fantastic. Once I arrived for my appointment Tyler had me change (by the way, they have showers on-site). Next he took some baseline measurements for height and weight. After answering some questions they had me get on the bike where they fitted the heart rate monitor and head gear. The test works by measuring oxygen, carbon dioxide and the amount of exhaled air. A mouthpiece with a hose attached routes your breath through a machine. Although the setup can look a bit scary, it's pretty easy to get used to.
The test protocol was pretty straight-forward. We started with a couple minutes of warmup. The bike is set to require a specific amount of power no matter your cadence. My job was to try to keep my cadence above 60 as the power required to pedal increased. About every minute, Tyler increased the power by 30 watts. Both Tyler and Dr. Eisenmann yelled encouragement while I pedaled through higher resistance levels. Eventually, as Dr. Eisenmann says, the bike always wins. Indeed, it did. As so many other athletes before me, I claimed I could have gone longer.
My VO2 max landed at about 54.5 ml/kg/min, but that wasn't what I was interested in. I wanted to know where to most efficiently produce power for distance racing. That number was more challenging. The low intensity numbers at the beginning of the test were clearly inflated, and the range available before we switch to 100% carbohydrate burning is surprisingly small. Dr. Eisenmann explained that nervousness at the beginning of the test can skew low-end results. Although he offered to re-schedule the test with an alternate protocol, I declined for now. I did get some ballpark numbers, which was my goal. They weren't good.
At a heart rate of 159, 63% of my calorie burn is already coming from carbohydrate. Based on a ventilatory threshold (which is different than, but often correlates with lactate threshold) of 188, a heart rate of 159 puts me smack in the middle of training zone 2. In the middle of zone 3, my carbohydrate to fat burn is about 80% to 20%. If I wanted to stay at a 50/50 fat to carbohydrate burn, I would need to stay right on the line between zone 1 and zone 2 and produce about 145 watts. This isn't very realistic for racing, even for a long race. Instead…I need to start training to eat better on the bike.
I intend to do a running test in the near future, and I'll request the protocol that Dr. Eisenmann suggested for my next bike test. That protocol included 3 minute segments instead of 1 minute segments, and reduced load increases by about 15%. Although my results were a bit disappointing, they're informative. I'd much rather understand where I'm at now, than in the middle of a full distance triathlon when I run out of fuel. As the date for Louisville 2015 gets closer, I'll request another set of tests with the altered protocol. My VO2 max should have increased quite a bit by then, as well as ventilatory maximum. Both should indicate more efficient fat burning, and an improvement in VO2 max should indicate a successful training program.
I'd like to thank Tyler, Connie, and Dr. Eisenmann for their help, and I would recommend the same test to other distance athletes. $75 is a reasonable amount to pay for a much deeper understanding of your body. If you're interested in scheduling a test, you can find contact information at http://snapp.msu.edu/.