Sunday, August 11, 2013

Go to Health: Exercise 2013

New research on exercise is reported in the August issue of Scientific American. You probably know that the ‘runner’s high’ (also felt after vigorous dancing, biking, and many sports) is caused by the brain’s release of endorphins (opioid-like hormones that evoke pleasurable feeling). Recently, research has also shown that exercise increases our ability to concentrate, think and make decisions. Exercise increases the size of a part of the brain called the hippocampus. The specific part of the hippocampus affected by exercise is one that allows people to remember familiar surroundings. Animal studies have shown that exercise increases the level of chemicals responsible for triggering the growth of new neurons. A molecule known as brain-derived neurotrophic factor is responsible. Newborn neurons are thought to help with distinguishing between similar but different events and things. Think about this – go for a hike; create new brain cells!

New research on how exercise prevents heart disease goes beyond the lowering of blood pressure, lowering LDL cholesterol (the ‘bad’ kind) and raising HDL choesterol (the ‘good’ kind). The more important LDL related effect is that exercise increases the number of larger, safer, LDL particles and decreases the number of small, dangerous ones. A couch potato might have an identical cholesterol level as an active person, but be more at risk for heart attack because of the predominance of small LDL molecules.

Exercise is a key to keeping blood sugar normal. As you use your muscles, they need increasing amounts of glucose to fuel their efforts. The liver sends out more glucose and the pancreas releases insulin - to signal cells to draw glucose from the blood. As exercise becomes a daily habit, muscles grow more sensitive to the effects of insulin, so lower levels will accomplish the same result, and the pancreas does not have to work as hard to keep glucose levels normal. This is particularly helpful for people with type 2 diabetes, whose bodies have often become resistant to insulin. Recent studies show that combining aerobic exercise (like brisk walking) with resistance training (weights, leg presses, et al) is the best for keeping blood glucose normal.

We know that we should be exercising, but many Americans fail to achieve the recommended half an hour of moderate activity for five or more days a week. However, a recent analysis of six studies, totaling 655,000 adults tracked for about 10 years, found that people doing leisurely activities like washing the car or taking a stroll for 11 minutes a day had a 1.8-year longer life expectancy after age 40 than inactive people. Those who met the guidelines for moderate activity gained 3.4 years of life, and those who were active between 60 and 90 minutes a day had greater gains – 4.2 years. It seems that we evolved as creatures who moved – think about walking out of Africa to populate the rest of the world. If you find it hard to begin, get a dog. Then you’ll have to walk, and she’ll always love you.

Sadja Greenwood past issues at

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