For years elite athletes such as lance Armstrong have supplemented their training with nights spent at simulated altitude, usually in an expensive "altitude tent." The tents show so much potential for increasing red blood cell production -- the fuel of endurance sports like swimming, running, and cycling -- that not long ago the World Anti-Doping Agency considered banning them.

Here's the dilemma: Is sleeping in the tents cheating, comparable to taking banned performance-enhancing drugs? Or is it a legit way for lowland athletes to improve their training and compete with guys who live at higher altitudes? I had a more selfish question: What could it do for a weekend cycling nut like me?

A week after I called Colorado Altitude Training to request a loaner, 157 pounds of equipment landed on my doorstep. My wife Madeleine eyed the plastic-windowed bubble that swallowed our guest-room bed. "Maybe this is why Lance Armstrong can't stay in a relationship," she said. Clearly I'd be sleeping alone.

In my first tent-bound night, though, I hardly felt isolated: The system's electrical air-intake device, which reduces the amount of oxygen in the air by trapping O2 in a molecular sieve, groaned like a gas generator. (CAT said the sound-dampening springs were likely damaged during shipping.) Rarefied air traveled into the tent via a flexible tube that emitted a rhythmic, exhale-like hiss.

After parking the intake unit in the garage I slept like a baby, at the equivalent of 4,500 feet above sea level. While I slept my body adapted to its new low-oxygen environment by growing new red blood cells and increasing its capacity for oxygen delivery. Each night I adjusted the chamber's oxygen level until it reached the equivalent of 8,200 feet, which research indicates is optimal for red blood cell growth and VO2 max development. Each day I did my usual workouts, and I often ducked into the tent for a while to read and work on my laptop.

After three weeks, I felt as if I had a third lung. I blazed through a three-mile time trial 5 percent faster than I ever had, and I finished top-15 in my category in a hill climb. During the race I quickly caught my breath on the flat spots, then felt ready to pound away again. The tent worked -- but I still had to train hard. After intense debate the World Anti-Doping Agency decided not to ban altitude tents, at least for now. My wife, on the other hand, wasn't so sure. Let's just say we were both happy when the bubble boy emerged from his tent for good.