Deep in the pain cave, without a flashlight.
Not that it would help, anyway. Light itself isn't the problem here. In fact it is your eyes, and your brain, that are failing you now.
An intense effort on the bike can cause temporary vision problems. The experience is somewhat surreal; the loss of the rather important bodily function of sight, as a direct result of your own actions, might make some think twice about repeating those actions.
Extreme effort can manifest itself as a loss of peripheral vision, double vision, or loss of focus depending on the individual, and the scenario.
But why?
"Basically, you aren't able to get nearly enough oxygen to the brain," said Trevor Connor, a physiologist and coach with the Pacific Cycling Center in Victoria, British Columbia. The result, he says, is the deterioration of vision.
"Your body is always trying to maintain balance. Blood pressure, sugar levels, everything," Trevor said. "When you exercise, you are throwing a challenge at your body, taking it out of balance, and your body is forced to do its best to keep you level."
"When you really push the intensity, forcing yourself to go over your natural state, your blood is pumping so fast that it can't fully oxygenate, and pumping through the brain so fast that the brain can't take the oxygen out of it that it needs. You are also opening up more blood vessels elsewhere in the body, making it more difficult to get the required blood volume up to your head."
Normally, the brain gets priority over everything. But at some point the amount of oxygen moving throughout the body is not only insufficient for your screaming, anaerobic legs; it becomes inadequate for normal brain function as well. Just as muscles scream when they are starved of the oxygen they need, so does the brain. It just screams in a different way.
But what can we, as cyclists, do about it?
Let's be honest, listening to our bodies has never been a strong suit. Stop racing the pursuit? Well, the UCI is having a go at that one. No more crits or 'cross? Not likely. Self-punishment is part of the game; we just need to learn to live with it through training.
And live with it we can, according to Connor. He points to a bundle of research into the psychological aspects of fatigue, most of which suggest our minds do, in fact, play a huge roll in what we may assume to be physical fatigue or exhaustion.
"The best way to deal with the sort of pain that accompanies tunnel vision is to break it down into smaller chunks of time," Connor said. "If you're seriously hurting with 60 minutes left in a race, your head will want to shut things down. Break the pain down into short intervals. Hurt for another two minutes, then two more. Pretty soon you've tricked yourself into sticking that wheel far longer than you would have otherwise. And who knows, maybe the field has slowed a bit at that point."
Mental strength is key, but physically preparing for vision-debilitating efforts isn't such a bad idea either.
Top professionals, like Scott Zwizanski of Kelly Benefit Strategies, are adept at pushing pain aside, and they all have their own methods for doing so. "If I'm doing intervals in training, I think about a rival, or someone who is a better than me, and the hard work I know they're doing. I know I have to work to beat that person," Zwizanski said. "In a race, it's a little different. You learn how to suffer in training, so you just run on autopilot in races. You just take your head out of it."
Mental strength is key, but so is physically preparing for vision-debilitating efforts. Specificity is king, says Connor.
"Simulate efforts similar to those that might push your brain over the edge," he said.
Connor recommends short, intense intervals with equally short recovery. Or, even better, find a fast group ride or practice race and "put yourself in the hurt box, over and over again. Hitting up a practice race and attacking repeatedly is much easier, mentally, than heading out for a bunch of 60-second intervals, with similar effect."
In other words, the only way to get used to hurting is to hurt. To train your body, and your mind, just head into the pain cave--no flashlight required.