Unit 21 Human Biology【美文阅读】 Nearly third of children globally are couch potatoesAmerican children aren't the only couch potatoes with nearly one third of children globally spending three hours a day or more watching TV or on computers ， according to a study of over 70,000 teens in 34 nations.From Argentina to Zambia ， Regina Guthold of the World Health Organization in Geneva and her colleagues found most children aren't getting enough exercise and it made no difference if they lived in a rich or a poor country.“With regards to physical activity levels ， we did not find much of a difference between poor and rich countries，”Guthold said.“Growing up in a poor country does not necessarily mean that kids get more physical activity.”They study looked at 72,845 schoolchildren aged 13 to 15 from North and South America，Asia，Europe，and the Middle East.The children were surveyed between 2003 and 2007.The researchers defined adequate physical activity as at least an hour of exercise outside of gym class at least five days a week.Children who spent three or more hours a day watching TV ，playing computer games，or chatting with friends－aside from time in school or time spent doing homework－were classified as sedentary(惯于久坐)．The researchers found only one quarter of the boys and 15 percent of the girls were getting enough exercise by these definitions.A quarter of boys and nearly 30 percent of girls were sedentary and didn't get enough exercise with girls less active than boys in every country aside from Zambia.Uruguay had the highest percentage of active boys，at 42 percent，while Zambia had the lowest，at 8 percent.Girls from India were the most active ， with 37 percent meeting exerc...
