8 2. We need air to do work. When we do more work, we need to take in more air. So we breathe harder immediately after exercise. Our breathing comes back to normal a little whileafter exercise, once the body stops doing extra work.
3. When we jump, we bend our knees, our feet push against the ground and then our body takes off from the ground. We then land on our feet. When we run on the spot, we rapidly raise our legs alternately into the air and then bring our feet back to the ground. When we touch our toes, we bend forward from the waist, stretch out our arms, swing to the side and alternately touch our toes with fingertips of opposite arms. Chart 1: Work done by muscles in the human body
4. All these actions that are performed during exercise are carried out using the muscles in our body. It is our muscles that bring about movements in the body as is shown in the chart of how our muscles work (Chart 1). During exercise, our muscles carry out work. The extra air that we take in after exercise is used toreplenish the energy in these muscles.
5. When we conduct experiments, we should be careful in making observations and recording them. If we need to compare observations in an experiment, all conditions, except for the one being compared, should be kept the same. In this activity, we compare breathing before and after exercise. When we sit quietly, it is obvious that we take more breaths in three minutes than in one minute. The greaterthe time we observe, the more the number of breaths taken. 6. In order to make a fair comparison of breathing speed before and after exercise, we should count the number of breaths taken in the same time period. So, if we count the number of breaths taken in one minute before exercise, we should count the number of breaths taken in the same time after exercise, i.e., one minute. Similarly if we count breaths taken in two minutes before exercise, we should count breaths taken in two minutes after exercise too. Only then can we arrive at a correct conclusion.
KEY MESSAGES
When we exercise, our muscles do more work than at rest. Since our body works harder during exercise, we breathe harder immediately after exercise to take in more air. To arrive at a correct conclusion in an experiment, we need to compare similar quantities.
LEARNING CHECK Why do we breathe faster during exercise? Agastya International Foundation. For Internal Circulation only. Request to Readers- Kindly mail details of any discrepancies or mistakes to handbooks.agastya@gmail.com