Sports can help you keep fit and close to nature. However, whether you are on the mountains, in the waves, or on the grassland, you should realize that sport you choose might have great influence on the environment. Some sports are _ . Golf, as you may know, eats up not only large areas of countryside, but also lots of water. Besides, huge amounts of energy are used to keep its courses in good condition. This causes major environmental changes. For example, in the dry places of Portugal and Spain, golf is often held responsible for (...) serious water shortage  in some local areas. There are many environment-friendly sports. Power walking is one of them that you could take up today. You don't need any special equipment except a good pair of shoes, and you don't have to worry about resources and your purse. Simple and free, power walking can also help you stay healthy. If you walk regularly, it will be good for your heart. Experts say that 20 minutes of power walking daily can make you feel less anxious, sleep well and keep thin. Whatever sport you take up, you can make it greener than by using environment-friendly equipment and buying products made from recycled materials. But the final goal should be "green gyms." They are better replacements  for traditional health clubs and modern sports centers. Members of green gyms play sports outdoors, in the countryside or other open spaces. There is no special requirement for you to start your membership . And best of all, it's free. What does the phrase "  _  " in this passage mean in Chinese?
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