Perhaps that acclimatization explains the steady — and voluntary — procession into the real-life sweat shop that goes by the name of Bikram Yoga in Cockeysville.
Barbara Brutzman leads between 10 and 15 classes a week in "hot yoga" in which the combination of extreme heat (105 degrees) and humidity (40 percent) is thought to make the body more flexible and thereby able to stretch more deeply. Perhaps not so coincidentally, each class lasts for the 90 minutes that the Dutch scientists described as optimal.
Brutzman, who often spends six hours a day in the super-heated studio, can't count the number of post-workout conversations she's overheard that begin, "You know, it's really not that hot outside."
Abby Aldrich, who has been practicing Bikram yoga for five years, adds that her workout has indirectly saved her money on utility bills.
"I keep my apartment six degrees warmer than I did five years ago when I started doing hot yoga," she says. "Now, it's set at 78."
It's even possible that the same process of gradual acclimatization — or the lack of it — gave history a slight nudge on the side of the U.S. during the War of 1812.
As Vincent Vaise, a park ranger stationed at Fort McHenry, describes it, the British were unlucky enough to sail up the Chesapeake during a heat wave in late August 1814.
Accustomed to a far more moderate climate, the soldiers were marooned in their ships on all that shiny, heat-reflecting water. They termed it "the oven on the Chesapeake Bay," Vaise said.
The Brits complained that it was hotter in Baltimore than it was in Spain. They described Maryland as unfit for human habitation.
Not that the American forces had it easy. They were running about tending fires and loading cannons while wearing uniforms made from thick, dense wool because cotton was then prohibitively expensive.
At the time, Vaise said, Fort McHenry had several hundred fewer trees providing a shady respite than the site does now.
Nonetheless, the Americans had a key advantage. As native citizens, they'd long grown accustomed to sweltering through Baltimore summers.
"Some of the British soldiers did go down to heat stroke," Vaise said. "Some of them died. The Americans were all acclimated for the most part, so they were able to keep fighting."
Sun reporter Sean Varner contributed to this article.