We all know that we can get Vitamin D from sunshine. Long winters make it hard to get enough. People who don't get outside often don't get enough either. Without Vitamin D, we may develop weak bones and teeth. We can get certain kinds of cancer more easily, too. | Chapter 2 __ Skill A Practice 1 Step 1 Research has shown that just 30 minutes of exercise a day is enough to keep most people healthy. This does not necessarily mean 30 minutes of hard exercise at the gym. It could be 10 minutes of brisk walking during a lunch break or any other short break during your day that you can think of. You simply need enough of these short breaks to add up to 30 minutes over your day. Whatever the activity is it is vital that it make you breathe vigorously and produce sweat. You have to get your heart working significantly harder than when you are resting. Step 2 light exercise can lead to physical changes in the body - study of women who walked - slow walkers lost more weight why they exercised longer because talked with friends weight trainers say focus on taking your time when exercising Step 3 Lecture Light exercise more effective People walking slowly saw better results than those who exercised intensely Reading Need vigorous exercise A person needs to increase their heart rate significantly Step 4 The speaker says that even light exercise can lead to physical changes in the body. 1 This contradicts the statement in the reading that people have to breathe hard and sweat when they exercise. 2 As an example the speaker describes a study of women who walk. In the study women who walked slowly lost more weight than women who walked fast for exercise. 3 This indicates that the length of time exercising is important not how hard the exercise is. 4 In other words it is better to exercise slowly for a longer period of time than to exercise quickly just to sweat more. Practice 2 Step 1 Genetically modified GM food has many advantages. In agriculture for example GM crops can better resist various insects diseases and weeds without so much use of chemicals. This allows safer use of the land and the chance to feed more people because farms can produce more than before. Furthermore GM crops grow bigger always look perfect
