The Bonking Reality of Endurance Training

To acquire stamina, you gotta sufer

Last Saturday I went for a two-hour bike ride, my longest ride since last July and my longest sustained cardiovascular workout since last November. And right around an hour and 30 minutes into a very hilly route, I felt myself start the unstoppable downward spiral that leads to what we Americans call “bonking” (You British readers can stop snickering). Mind you, I was well hydrated, I was sucking down an energy gel every 40 minutes, and I set out on a full stomach. But, I still ran out of gas. Frankly, I knew I would; this is just another aspect of endurance training. And I’m sure as many of you set off on your first big hikes and trips of the spring, you will also experience the same light-headedness and complete energy shutdown that define bonking.

In a nutshell, this condition occurs because the body’s glycogen operation, the muscles’ number one fuel source, wasn’t prepared. In the case of my bike ride, I went well past the usual length of a workout—by over 45 minutes—and tapped out my glycogen stores. I paid the price for skipping the steady progression of a training plan where I increase my mileage by 10 percent a week and my body easily adapts to the extra work by storing more glycogen in my muscles and doling it out more efficiently.

But here’s something cool about bonking. The body adapts quickly to it. I bet if I did the same ride two weeks from now without changing what I ate or how much I drank, I’d have no problem riding strong for the duration.  My body would now be “ready” to handle this long-term workout, and I could now set my sites on even longer rides.

The same goes for climbing, backpacking, or hiking. That first 10-hour-plus climb up and down a mountain will waste you no matter how well you eat and hydrate. However, don’t use that experience as a barometer of your next climb this year. In all likelihood, the next time you set out on an all-day adventure, you’ll probably motor up and down the trail with ease.

That said, there are some things you can do to reduce the depth of a bonk.

• Go slower when you’re going longer: Take it easy. You should never feel like you’re working too hard during the first long day of the year.
• Two hours before exercise: Drink 20 ounces (a water bottle’s worth) of sports drink. That way you’ll have a reservoir of fluids and glycogen to tap before you head out.
• 20-minutes before exercise: Top off with 10 ounces of sports drink. You’re just topping off your fluid, sodium, and carbohydrate levels. Doing this delays the need for your body to pull fuel from your glycogen stores a little bit longer.
• During exercise: Stay hydrated and fueled with an hourly water bottle’s worth of an electrolyte-laced carbohydrate sports drink or combination of 10-ounces of water and an energy bar an hour or 2 gels every 20-30 minutes. The quickly digestible calories from the drink, bar, or gel will slow down the rate at which you burn through glycogen stores. NOTE: On hot days, you could need twice as much fluid and electrolytes.
• As soon as you come off the trail: Drink a bottle of sports drink to restore your fluid, fuel, and electrolyte levels. You’ll bounce back faster because of it.

Over the last decade Grant Davis has been writing and editing articles about health, fitness, and nutrition. He lives in Colorado Springs, Colorado.