醫(yī)學(xué)知識英語閱讀

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　　醫(yī)學(xué)英語閱讀：保護心臟

　　Tend your ticker with a heart monitor

　　Heart-rate monitors help put workouts in perspective.

　　They are “the ultimate personal trainer,” said David Wright, a certified fitness specialist and Army master fitness trainer. “The main reason for using a heart-rate monitor is for safety.”

　　A basic heart-rate monitor consists of a transmitter strapped to the chest or over the breastbone. It send signals to a receiver, usually worn on the wrist. The receiver displays the heart rate – the rate at which your heart is sending blood to your muscles and lungs.

　　A monitor also can reduce the risk of injury.

　　“What happens most of the time,” Wright said, “is that the novice will go out and practice at a rate that is way too high. When you overexert yourself, you are at risk for injury, and you could be putting your heart at risk.”

　　The monitor “can also be used as a way to motivate,” Wright said. “You are able to assess and monitor your own training. It is something a beginner can use and an advanced runner can use.”

　　Most important, once you buy your monitor, you must find the proper heart rate for your workouts. To do this, Wright recommends this formula:

　　· Determine the maximum heart rate by substracting your age from 220. For example, a 50-year-old would have a maximum heart rate of 170 beats per minute. You do not want your heart rate to exceed the maximum during exercise.

　　· Determine you resting heart rate. Sit quietly in the morning before consuming stimulants such as caffeine. Count the number of times your heart beats in one minute. A 50-year-old might have a resting heart rate 0f 75 beats per minute.

　　· Substract the resting rate from the maximum. (170-75=95 beats per minute). The 95 beats per minute is your hear-rate reserve.

　　· Multiply the heart-rate reserve by the intensity level at which you want to exercise. For example, a beginner might want to exercise at a 60 percent intensity level (95 beats x 60 percent = 57 beats per minute).

　　· Add the resting heart rate. (75) to the intensity level (57). In this example, 132 is the target heart rate.

　　· “The 50-year-old man would not want to go above 132 beats per minute when he exercises,” Wright said. “Most importantly, whatever you do, find your zone. If you exercise any higher than the recommended heart rate, you put yourself at risk for injury.”

　　醫(yī)學(xué)英語閱讀：濕氣才傷人

　　Tell someone enduring life in the desert or jungle that “it's not the heat; it's the humidity,” and you might find yourself with a heated conversation on your hands.

　　High temperatures of any kind often are uncomfortable and can be deadly, especially when supplemented with 50 pounds of gear on your back.

　　But humidity takes on a different meaning when you strip away the heavy equipment, add running shoes, shorts and a T-shirt and hit the road.

　　Of course, low humidity and high temperatures also might produce serious heat-related injuries such as dehydration, heat exhaustion or heatstroke. If the body can't cool itself and isn't properly hydrated, even in mild temperatures, all of these are possible.

　　But on the road – from a 5-kilometer race to a marathon – humidity is even more devastating to the unprepared runner.

　　When running, the body's goal is to cool itself. As its temperature rises, the body begins to perspire; the air causes evaporation of perspiration and cools the body. Increase humidity, however, and body heat rises while the evaporation process – and workout progress – slows.

　　A main reason is that moist air does not provide a “drying” effect on damp skin. With limited ability to evaporate moisture, the cooling effect is reduced, which can lead to heat exhaustion or heatstroke.

　　Remarkably, however, high humidity's most noticeable side effect might be a misconception.

　　Thick, moist air typically gives runners the impression they can't get enough oxygen with each breath. But the “limited oxygen” theory is just that, a theory. The body holds onto a small percentage of oxygen with each breath, and the rest is exhaled. So whether the humidity prevents the intake of adequate oxygen is up for debate.

　　Breathing more likely becomes labored not because of a lack of oxygen with each breath, but because the body is running hotter and needs more oxygen to cool itself.

　　A few adjustments and a bit of acclimation can reduce high humidity's effects during a run.

　　First, avoid running during the hottest part of the day, between 11 a.m. and 6 p.m. Many runners prefer evening workouts, and this is better than in the heat of the day, but early-morning runs usually are cooler, and overall air quality is better.

　　Second, hydration is even more important in high humidity, since the body's cooling ability is reduces.

　　Finally, humidity's negative effects decline as runners become acclimated to a warm, moist climate. It doesn't happen overnight, so maintain workout schedules and give the body at least two weeks to adjust.