5/4/20
As a cyclist, it's easy to wonder where the line is between fueling your body and fasting to train a healthy metabolism and increase power/weight ratio. As I've come to realize, it's a delicate balance that should lean on your goals and habits. Before exploring the diet and planning side, it's important to understand what proper eating really does to increase athletic performance in the first place.
As we've discussed before, the body relies heavily on glucose and fats in endurance exercise, while protein's role is to repair the micro-tears that come from pushing your muscles. After you eat a carbohydrate-rich meal, the carbs are broken down to glucose, at which point they are stored in the muscles and liver as glycogen. When the liver is overflowed with glucose, it's then stored as fat, some long term consequences of this being NAFLD and obesity. In my post about Zone 2, we talked about which fuels are correlated with each training intensity. Basically, lower intensities use more fat, while the most intense movements use almost all glucose. This explains why it's so hard to maintain an "all-out" or sprint for very long. Past a point, the body not only physically hurts by way of the burning pain that lactate in the bloodstream causes -- it also runs out of the fuel source that allows that intense effort. Still, the liver can produce glucose "on-demand" by turning other nutrients into glucose through hepatic gluconeogenesis, but this process can't sustain the rate of glucose usage in the higher training zones. Additionally, the lower zones can lean heavily on fat, which even the skinniest of us have plenty of.
So let's revisit that point in your workout. You're feeling good today, so you decide to really push yourself. You decide that the punishment of Zone 5 is worth the satisfaction. But you were wrong. Some time into the ride, your bike sounds like it's rotating enough to lift you off the ground, but all of a sudden, you lose all ability to generate any force out of your legs. You "bonked," as they say in cycling. Put simply, lactate buildup in your leg muscles combine with lack of glucose to stop you in your tracks. At lower zones and longer rides, it's more likely that you're out of fuel, as a properly nourished rider could continue for a 12 hours or more in Zone 2 or lower. On the other end, a twenty second sprint becomes unbearable from the anaerobic lactate buildup alone rather than glycogen depletion. Protein can be made into glucose in the liver, but its main function is to supplement the repair of muscle fibers; their level of damage is correlated with the intensity of the workout.
With all of this in mind, how do we find balance in our nutrition between fasting and fueling? It really comes down to habits and goals. In all training, these habits are intensity, duration, and frequency. With a high frequency, intensity, and duration, professional cyclists depend on huge amounts of carbohydrate consumption so that they're ready on short rest to perform at their best. Protein is especially important for taxing rides of high intensity that leave you sore; your muscles need it to repair and come back stronger. On the other hand, a cycling enthusiast with less frequent rides may want to prioritize their metabolic efficiency by fasting each day and before some rides. Although, even the most successful riders like Lance Armstrong used seasonally scheduled fasting to reduce their weight and increase speed.
The world's most efficient metabolisms are in world-class endurance athletes. They can consistently eat more carbohydrates than anyone (think around 750 grams) per day and stay lean because they're always depleting/replenishing their glycogen stores and have the most efficient mitochondria for fuel partitioning. However, they wouldn't perform at that level on a low-carb plan like the ketogenic diet.
On the other side, a person with Type 2 Diabetes has inefficient mitochondria and therefore lower performance levels. Their goals and habits are of course different from the world-class athlete, but someone like this may prefer to operate solely off of ketones and fat in ketosis. They could fast heavily and use Zone 2 training only to reduce insulin resistance and better their metabolism.
My plan is engineered around each day and my short-term goals. I find it fun to train and increase my FTP, even though I have been using fasting as another tool to realize a healthy metabolism. I schedule certain rides throughout the week before breakfast and use those as Zone 2 rides to train my metabolism. Other days, I plan carbohydrates before my ride to maximize my output and realize more muscle gain. Obviously, for an FTP test or long rides, I'll employ this tactic.
For in-ride fueling, intensity and duration are keys. Particularly intense rides with decent length or long rides will force depletion of glycogen stores. As a rule of thumb, you should consume carbs in rides around two hours or longer to keep from bonking. The quickest acting are the "goos" or sports drinks.
After glycogen depleting rides, I encourage you to take that opportunity (especially if you have another ride soon) to eat as much as you want and refill your fuel tanks that are your glycogen stores. Hey listen, we all love food and appreciation of it can be engineered, too. At the end of the day, it's always important to identify what your goals are, what makes you happy, and then start to think about building your plan.
- Jack
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