Question

1. explain how to measure the intensity of a physical activity. 3. what is the target heart rate for a 15 - year - old engaging in moderate - intensity physical activity? 4. what weight should you select when using free weights or a weight machine? 5. what is the purpose of engaging in aerobic activity before stretching?

Explanation:

1. Physical activity intensity can be measured by heart - rate monitoring (comparing to maximum heart rate), rating of perceived exertion (self - assessment of how hard one feels they are working), and metabolic equivalents (METs, which measure the energy cost of physical activity).
2. The maximum heart rate is calculated as 220 - age. For a 15 - year - old, the maximum heart rate is 220 - 15=205 beats per minute. For moderate - intensity physical activity, the target heart rate is typically 50 - 70% of the maximum heart rate. So it is 205×0.5 = 102.5 to 205×0.7 = 143.5 beats per minute.
3. When using free - weights or a weight machine, select a weight that is challenging but allows for proper form. Start with a lighter weight and gradually increase as strength improves, aiming for a weight that can be lifted 8 - 12 times with fatigue at the end of the set.
4. The purpose of engaging in aerobic activity before stretching is to warm up the body. Warming up increases blood flow to the muscles, making them more flexible and reducing the risk of injury during stretching.

Answer:

1. Heart - rate monitoring, rating of perceived exertion, and METs.
2. 102.5 - 143.5 beats per minute.
3. A weight that is challenging yet allows for proper form, aiming for 8 - 12 repetitions with fatigue at the end.
4. To warm up the body, increase blood flow to muscles, and reduce injury risk during stretching.