In 2007, Harvard psychologist Ellen Langer wanted to understand the mindset of hotel cleaning staff. Specifically, she wanted to study the relationship between exercise and self-image. Maids made for a perfect test group, given they spend entire days working out, even though they might not realize how much physical energy they’re actually using. Do they consider their jobs healthy?

Eighty-four attendants from seven different hotels took part in the study. The experimental group was told “the work they do (cleaning hotel rooms) is good exercise and satisfies the Surgeon General's recommendations for an active lifestyle,” while the control group was not informed of this fact. After four weeks, the group primed to believe they were exercising lost weight and saw decreases in body fat, blood pressure, waist-to-hip ratio, and body mass index. The same did not occur in the control group.

While Langer speculates that the placebo effect played a role, this mindset shift is important. Instead of treating work as drudgery, the women who shifted their understanding of their jobs experienced positive health benefits. This could have broad implications in how we treat fitness, opening up new avenues for staying healthy while engaged in seemingly un-athletic activities.

One such phenomenon is plogging. In Sweden, runners are combining exercise with environmentalism by picking up trash along the way. And it's catching on. Plogging is becoming so popular internationally that the app, Lifesum, added a tracker to its interface.