问答题 Sweating on purpose is becoming an elite phenomenon.In a darkened room at the edge of downtown Washington,D.C.,electronic music pulses over the speakers as a crowd of mostly sweaty young women bop up and down.Sadly,this is not a drug-fuelled rave,but rather a mid-afternoon spin class.It is run by Soul Cycle,which promotes the idea that riding an exercise bike to loud music is akin to entering a"soul sanctuary".The experience,involving awkwardly lifting weights while cycling,costs about S35 for 45 minutes,which does not deter its well-heeled customers."Some of the women pay a lot of money to go here,"says a staff member,her eyebrows raised.According to figures from the International Health,Racquet and Sportsclub Association,an industry group,gym members now number 54m,up from 45m in 2009.Twice as many Americans subscribe to gyms as in the mid-1990s.