These days there is only one right answer when someone asks you what you are doing after work. Hitting the gym With an explosion of apps, clothing, devices, and countless DVDs, fitness has never felt more modern, and the gym is its holy laboratory, alive with machinery, sweat, and dance music. But we are far from the first to pursue bodily perfection--the gymnasium dates back 2,800 years, to the very beginnings of Western civilization. In The...