This is Your Body on Base Training
In an era where Cross Fit, Tabatas and other HIIT style training often hog the spotlight, it’s easy to overlook the decidedly unsexy, Zone 2 rides and go straight for the gusto every time you ride.
In an era where Cross Fit, Tabatas and other HIIT style training often hog the spotlight, it’s easy to overlook the decidedly unsexy, Zone 2 rides and go straight for the gusto every time you ride. – By Selene Yeager
Don’t. Steady, moderate-paced, base-building rides perform their own unique metabolic magic you don’t want to miss out on. Just ask Inigo San Millan, PhD, of The University of Colorado Sports Medicine and Performance Center (CUSM&PC) in Boulder, Colorado, who has helped thousands of riders, runners and swimmers get faster by slowing down.
“Zone 2 training is harder than a recovery ride, but not so hard that you can’t talk the whole time. Depending on your fitness level, it’s between 55 to 75 percent of your VO2 max intensity or about a 5 to 6 on a 1 to 10 scale,” says San Millan. “This is where you’re burning the most fat for energy before you cross the threshold into more carbohydrate burning. The majority of your rides—about 75% of your training time during base training period—should be here for the best training benefits. Stick to it 3 to 4 days a week in the first several weeks of training and you’ll see your watts go up as your heart rate and perceived exertion remains the same.”
Type I fibers are home to the bulk of your muscle’s energy producing mitochondria. When you devote time to building your base, you’re actually stimulating mitochondria growth and improving their function, so you become an even better fat burner. That’s a key benefit of building a big base. Your body becomes so good at burning fat that you preserve your precious glycogen stores, which gives you the energy you need to go hard at the end of a long ride or race.
Because you’re using lots of oxygen during base training, your body adapts to make it easier for you to get as much oxygen as possible into your working muscles with every heartbeat. That means your heart gets stronger to pump out more blood per beat and your body lays down a larger network of capillaries within your muscles so you can deliver more oxygen and nutrients and carry out more carbon dioxide and metabolic waste products per minute.
Your Type I, slow twitch fibers do more than burn fat, they also clear lactate. It works like this: when you ride harder than your Type I muscles can handle, like in a sprint, the fast-twitch Type II muscle fibers step in and start blasting glucose from glycogen (stored carbs) for energy. The byproduct of this process is lactate. By now you know that lactate is not the enemy, but rather a fuel source that can be used to make energy in your muscles and other cells— but the hydrogen ions associated with lactate can accumulate and interfere with muscle contraction, which is when you slow down.
You need to be able to clear lactate out of your fast-twitch muscle fibers ASAP, and that’s your Type I fibers’ job. They do it through a process called the mitochondrial lactate oxidation complex (mLOC)—which is indeed complex. In short, your fast twitch fibers shuttle lactate using special transporters called MCT-4, where it then hitches a ride into your slow twitch fibers (which contain the most mitochondria) via their own special MCT-1 transporters. Once inside the slow-twitch fibers, the mLOC works its magic to re-use lactate for energy. Base training increases these transporters and your mitochondria, improving the whole mLOC system so you can clear more lactate faster and go harder for longer.
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