EUGENE, Ore.—Donn Cabral logged onto Craigslist this winter and made an investment in his future. He bought a high-altitude tent, lugged it to his dorm room at Princeton University and plugged in the generator, which made a low whirring sound. His roommates were not particularly enamored with this development.

Nevertheless, for five months leading into the U.S. Olympic track and field trials, Cabral slept and studied in his high-tech tent, which simulated about 12,000 feet of altitude and formed a sort of canopy over his bed....