Last afternoon, Rupert announced that he had to watch his diet. Because he wasn’t cycling that fast anymore, he wasn’t burning the same amount of calories. That didn’t make any sense to me. Wouldn’t cycling from A to B always require the same amount of energy, no matter whether we’re going faster over shorter time, or slower over longer time? Remember Einstein’s famous E=mc2? Wouldn’t that violate physics, if we used different amounts of energy for the same distance?
“It’s nothing to do with physics, but our internal biology”, some people suggested.
That made even less sense to me. Whatever our internal biology did, it was still energy after all.
“It’s because of air resistance”, others proposed.
Again, that didn’t make sense to me. Whether we face it faster or slower, it’s still the same amount of air we’d have to cycle against.
“Air resistance is exponential”, Peter tried to explain.
“It’s nothing to do with physics, but because of our body engine, internal biology”, others repeated.
By that time, I no longer knew what to believe. No answer seemed satisfactory. So I consulted Dr. Google. Peter had been right.
“I have to apologize”, I told Rupert in the morning. He looked at me confused. “I said your calorie theory was bullshit, but I’ve been proven wrong.” And even if right, I know I shouldn’t have called it BS . . .
“So what have you found out?”
“That air resistance is an exponential function of speed, not linear. That was the missing link that I didn’t know.”
Hence, when we bike faster from A to B (even if it takes us less time), we burn more calories than cycling slower over more time. Therefore, we can/have to eat more when we race, but don’t feel that hungry when we take our time—theoretically.
Practically, I personally haven’t noticed that correlation with my own eating behavior—I eat all the time either way, and more now that I’m not pushing so hard than in the early days when I was truly racing. But then again, perhaps that’s because I’d used up all easily accessible fat in the early days, whereas now I need to replenish lost energy—which would bring our internal biology back into the equation . . .
Stage 82: Springbok – Kliprand (South Africa), 153km
Road & traffic condition:
Dirt—at times quite bad deep sand and corrugation, some sections relatively good. Many riders found today one of the worst dirt days we’ve had so far. It requires constant alert in order not to fall, or catch oneself quickly when we get stuck in the sand. Several people have come off their bikes today and the past days—without injuries other than some scratches, fortunately.
Pleasant temperatures up to ca. 25 °C, but moody wind—at times tailwind, at times heavy headwind, even though we haven’t changed our overall cycling direction. Cold in the evening—jackets and thermals have made their comeback.
BBQ chicken, potatoes, boiled mixed vegetables, coleslaw—pretty good!
Difficult riding day. Lots of flies bothering us while cycling. Not the nicest campsite—back to ice-cold shower and only two bathrooms/toilets for all of us. But we’re all handling it well—some by taking the truck into camp and drinking beer, others by being relieved once we’ve reached camp, . . . knowing that we’ve had worse and keeping our positive disposition.
I haven’t found today as hard as most people—probably because I didn’t stress for time, kept myself entertained listening to audiobooks while riding, took short breaks when I needed them, and—most of all—my wide knobbies probably make it a lot easier for me to cycle in this difficult terrain and not fall when the sand gets deep, at least after I’ve finally gotten the hang of it.