A、Hiking is particularly beneficial. B、They should set a time limit to their exercise. C、There are other ways to work out. D、The

Wall-to-wall mirrors in gyms and dance studios might stop women getting the exercise they need because women who work out in front of a mirror get discouraged and feel tired, Canadian researchers said. The study, published in the journal Health Psychology, focused on young women who exercised less than 15 minutes a week. It found that, regardless of how they viewed their bodies, women who worked out in front of a mirror felt worse: or no better, and less at peace after 20 minutes of activity. The survey questioned 58 women with an average age of 22—young enough to be concerned about body image. Participants took turns on fixed bicycles, working out either in front of a mirror or with the mirror hidden behind. And whether the participant felt comfortable about her body or not, the outcome was the same— women who did not have to watch themselves exercise felt calmer and more positive at the end of their session.
    Still, lead author of this study, Kathleen Martin Ginis, stressed that mirrors can be positive and functional, because exercisers often need to see their form, or assess if they are using the correct muscles groups during strength training.
    But things were different for beginners. Martin Ginis suggested gyms provide areas without mirrors to encourage beginners. "Women don’t need to exercise in a gym," she said. "Thirty minutes of walking, or hiking is good too. There are other ways to get your exercise."
19 According to researchers, how do women feel when they exercise in front of a mirror?
20 Why did the survey choose women with an average age of 22 as participants?
21 What advice does Martin Ginis give to the women?