Most people didn't see exercise as necessary until the mid-20th century. Food scarcity meant people didn't overeat, and it didn't make sense to try to burn off the calories.

However, industrialization changed the nature of work and food production. Fewer farmers were doing physical labour, and more people were doing office desk jobs. The growth of automobile culture, the suburban sprawl, and the popularity of television, all led to a more sedentary lifestyle.

Some entrepreneurs and trainers played a vital role in the rising exercise culture.

• Health clubs were popularized by the Vic Tanny Gyms chain.
• Weight-lifting for women was popularized in the 1930s and 1940s by female-bodybuilder Abby "Pudgy" Stockton.
• In 1974, the E...