Base miles season is here again, and with longer rides comes
the need to focus on calorie replenishment while training. A Ferrari will only go so far on a tank of
gas, once the tank is empty even the fastest most high performance automobile
will sputter to an untimely stop. The
human body is similar, but with a big difference: we have a huge reserve tank
(fat stores) but that tank is attached to the engine with a tiny hose and fuel
is administered in drips and drops.
Energy for the human body comes in three forms: carbohydrates,
fats and proteins. These are called the primary
macronutrients. In order to be usable
these three energy sources need to be broken down (i.e. metabolized) into
glucose. Fats and proteins can be broken
down into glucose, but it’s a slow energy consuming process, carbohydrates, on
the other hand, can be quickly converted into precious glucose. When it comes to fueling during exercise
carbs are our friends.
The body doesn’t store glucose but instead banks extra
glucose in the liver and muscles in the form of glycogen. The typical human body stores enough glycogen in
the liver and muscle tissues to fuel approximately ninety minutes of moderate
to high intensity exercise. Glycogen is
the body’s go to energy source. When the
glycogen stores become depilated the body begins burning fat for energy, even
the thinnest person has enough fat reserves to fuel days of low intensity
exercise, but the key words here are low intensity. Burning fat trickles the energy to the
working muscles, in other words it’ll keep you going but at a much reduced
pace. When you begin to rely heavily on
fat reserves for energy you’ve “hit the wall,” you’ve “bonked” (notice how
bonking doesn’t leave you dead on the side of the road, but instead reduces
your speed down to “I’m going nowhere” levels).
Bonking isn’t inevitable, you can avoid it by having a well
thought-out nutrition plan designed to continually replenish your glycogen
stores – kind of like continually stopping at gas stations on a long road trip.
Unfortunately developing a nutrition plan isn’t as simple as
eating the calories that you burn. A
calorie is only useful if your body can break it down and absorb the energy via
the digestive tract while maintaining a high level of physical exertion. Here is the key problem: the harder you work
the more you need the energy, but, conversely, the harder you work (i.e. the
higher your heart rate) the slower energy is released via the digestive
tract. In other words, as your heart
rate goes up the slower energy is released from your gut. If you keep shoveling food into a slow
digestive system you’ll end up with GI distress, a condition nearly every
endurance athlete is all too familiar with.
The trick to developing an on the bike nutrition plan is to
figure out what works best for you. In
the next series of posts I’ll throw out some ideas on what has worked for me and
what hasn’t, but in the end every body is different and you’ll have to
experiment to find out what works and what doesn’t.









