I first heard about the concept of metabolic efficiency when I went to the USAT coaching certification clinic. One of the speakers there was a sports nutritionist named Bob Seebohar who talked about this concept of how we can potentially manipulate our bodies into burning more fat during exercise. Why would you want to do this? Well, for anyone who has done a long (3+ hours) event, like a long-course triathlon or a century ride or something else where you are exercising for a long time, you may be familiar with the idea that your digestive system gets to the point where it decides it’s not happy with anything you ingest. When we exercise, our body shunts blood to our active muscles so they have the nutrients and fuel they need to keep working. However, this means we are getting less blood to our digestive system and our digestive system cannot process what we take in (very well, unless we stay at a low-enough intensity). So as our long event goes on and we take in more and more sports nutrition products, gel, sports drink, etc., the concentration of stuff in our gut just keeps going up and up while our body continues to shunt blood to our other muscles to keep powering our bodies forward. This is when things start to go south. For anybody who has done a long event, you’ve probably seen somebody doubled over along the course (particularly rampant at Ironman events) and unfortunately their nutrition is now coming back up (literally) because their body has decided to shut down. It goes like this: no fuel getting absorbed because we are exercising and taking in too much too fast resulting in a high concentration in our gut -> we feel worse and worse because no fuel is getting absorbed -> we take in more and more gel, etc. thinking that will solve the problem -> body shuts down and eventually forces contents of gut back up. Not pretty. What’s the answer? Burn more fat during exercise. Even a well-trained athlete only has maybe 2,000 calories of glycogen in their muscles and liver ready to act as fuel for exercise. However, even the leanest person has 80,000+ calories of fat to use to fuel exercise. You can see how 2K calories won’t last long if you are burning only sugar.
So how do we change all this? How can we make our bodies better “fat-burners?” In Bob Seebohar’s book, he suggests, and presents a fair amount of evidence that you can do this by:
1) Training at an aerobic intensity
2) Manipulating the macronutrients of your daily nutrition
Item number 1 is fairly straightforward – most of your training should be at an easy/moderate intensity. Do the hard stuff sparingly (for lots of reasons). Because of this, it may be easier to try improving your metabolic efficiency during a time of year when you are not racing as much and concentrating on building a big aerobic engine. Item #2 is about what you eat on a day-to-day basis MOST of the time. I say MOST of the time because I believe that if we are too black-and-white about anything, it can backfire. This is why most “diets” don’t work. If you completely cut stuff out, then it’s no good and our nature is to end up “falling off the wagon.” What you do on a consistent basis 90% of the time is key - keeping things simple and doing everything in moderation. In Bob’s book, he describes a periodized nutrition plan where the focus most of the year is on eating fruits and vegetables, low-fat protein, and healthy fats. You don’t need as much whole grain as you think. Sufficient carbs to support your training come from the fruits and vegetables (and other sources, dairy, etc.). Only when you are in a heavy period of training you supplement with some whole grains. This flies in the face of most of what has been preached to us endurance athletes for a LONG time. The entire sports-nutrition-product industry has been created to “fuel” our workouts. However, what do you think people ate prior to Gatorade and prior to Gu? Real food. Simply eat a well-balanced snack prior to your training sessions and then do the same immediately after. This is enough. During training, particularly if it’s easy/moderate intensity, we don’t need all the extra sugar. It teaches our body to be more efficient at burning sugar. And we know that burning sugar can only last so long. If we can be more metabolically efficient, we can go longer with a lot less risk of any GI distress.
How do we know or measure any of this? Do we have to just guess? I am fortunate to have a friend who actually IS a sports nutritionist and has the equipment and capability to do metabolic efficiency testing. Sheila Leard (www. MyNutritionZone.com) is a registered sports dietician and can perform this kind of testing. By analyzing the content of what you breathe in and out, you can understand the blend of carbohydrate (CHO) and fat you are burning at different exercise intensities. This is VERY powerful information. For example, with a marathon on the horizon, using this data, I can understand EXACTLY what intensity (for running pace and HR) I can shoot for and be confident how much carbohydrate I am going to burn through the duration of the event. I now know what intensity to run for whatever duration I am interested in. I can also devise a fueling strategy based on this and practice it in training. The test is not complex or intimidating. You can do it either on the bike or on the treadmill and simply involves wearing a mask while you ride or run. Here’s a link to a video of me on the treadmill during the test: http://qik.ly/BE8pH3Nk3uESI5yqf4KsQsJ. You do an easy warm-up and then progressively increase the treadmill speed at set intervals, all the while, monitoring what’s called the Respiratory Quotient (RQ) via the mask and your heart rate via a heart rate strap/monitor. The RQ is the ratio of CO2 expired to O2 inspired and tells us how our body is handling the exercise intensity, by either burning mostly fat, some of both fat and CHO, or mostly CHO. The point where it changes to mostly CHO is called the crossover point. Ideally, you want to stay below this for much of your training, and combining that with daily dietary manipulations, you can teach your body to be more metabolically efficient.
My results were very informative. In the plot, you can see I was burning a decent mix of fat and CHO up until we took it from 8 (~7:30 min/mile) to 8.5 mph (~7:00 minutes per mile) at which point my body transitioned to burning mostly CHO. Not only that, now I KNOW how many calories I burn per minute and what the blend is between fat/CHO at each intensity. Perfect. I can come up with training and fueling plans optimized for my upcoming races! It takes out the guesswork and makes me confident I can achieve the goals and performance targets I have set for myself! I am very excited about this concept and continue to work on the dietary changes myself. With two toddlers at home and a busy life, I will admit, it is tough, but like I said, I try to do well MOST of the time. I am also very excited about this concept and using the metabolic information with the athletes I coach. Fueling in endurance sports is definitely a trial-and-error process, but this testing helps take the guesswork out of it and the athlete and I can work together to come up with a fueling strategy more specific to their race circumstances and goals.
1 comment:
Great post Jon! I've been testing out the ME concept as well (I had Bob Seebohar test me last month) and have been very happy with the results!
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