Gyms today have secured some of the most prime retail real estate around the country. That was not always the case.

For years, gym tenants were unwanted by mall landlords as they were believed to provide little value, attracting visitors who were unlikely to spend money at any of the shops in the vicinity.

Now, gyms are a valued addition to the tenant mix. Americans' focus on health and fitness has grown to such an extent that athletic apparel has become an acceptable form of attire, increasing people's willingness to shop after working out, the Wall Street Journal reports.

While many retailers have shuttered their doors due to e-commerce competition and declining foot traffic, fitness centers are on the other end of the spectrum as gym memberships skyrocket across the country.

More than 57 million people or 19.3% of the population belonged to a health club last year. Since 2009, memberships have increased by 26%. While gyms were long thought to be detrimental to the retail environment, consumer spending at fitness centers rose 3.7% in the third quarter compared to the year before, the WSJ reports.

This dynamic has made gyms attractive to landlords, especially as they look to reinvent themselves as entertainment destinations that offer a variety of activities aimed to draw shoppers.