Fit Facts and Figures
by Jerry Brainum
Pregnant women produce larger amounts of endorphins, body chemicals that reduce pain. Exercise also raises endorphin levels. So what happens if pregnant women exercise throughout their pregnanies?
Researchers in Italy had 18 pregnant women exercise on stationary bikes throughout their term. Another 18 pregnant women didn't exercise. Those who exercised had higher endorphin levels and felt far less pain during labor. (Am J Ob-Gyn 160; 3:707-12, 1989)
Medicine 82 percent of the 500 doctors polled declared that they regularly prescribe exercise to depressed or anxious patients.
We know that something about exercise makes people feel good, but the question is, exactly what is the mechanism involved? Several theories account for the uplifting mental effect associated with vigorous exercise. The most popular involves a brain chemical called beta-endorphin, which is produced in the brain under times of perceived stress, including the stress of exercise. Beta-endorphin is quite potent in its pain-killing effects, estimated to be I00 to 1,000 times more potent than morphine; but beta-endorphin does more than just relieve pain—it also induces a feeling of well-being.
The levels of beta-endorphin increase fivefold after just 12 minutes of vigorous exercise and remain elevated for 30 minutes after exercise.
Some people ascribe the recently recognized syndrome of "exerciser's addiction" to beta-endorphin, noting that when people afflicted with this condition don't exercise, they show symptoms similar to those seen during withdrawal from drugs.
Not everyone, however, agrees with the beta-endorphin theory. The skeptics say that there's no proof that high levels of beta-endorphin pass through the protective blood-brain barrier. In addition, when naltrexone, a substance that blocks the effects of beta-endorphin, is given to exercisers, they still experience the "good feelings" from exercise.
Another theory states that exercise produces a mental boost through increased secretion of other brain chemicals called catecholamines, particularly norepinephrine. This makes sense because mental depression often stems from a deficiency of this chemical. In fact, most antidepressant drugs work by
The motivation to exercise varies among different people. Some people exercise to lose weight, others to gain weight. Others are satisfied with their weight but want to add muscle tone or shape. Still another group exercises for rehabilitative reasons—for example, heart patients or people with arthritis. Then, of course, there are bodybuilders, most of whom ex ercise for competitive purposes—that is, bodybuilding competition. Whatever the motivation, however, all these people share one thing in common: Exercise makes them feel good.
The effects of exercise appear to be psychosomatic, or involving an interaction between the brain and body. This fact is well-known to physicians. In a 1987 survey appearing in the Physician and Sports
increasing the brain's supply of norepinephrine.
norepinephrine levels 10 times over base level; however, the level returns to normal 10 minutes after exercise ceases. Regular exercisers produce more of this stress-fighting substance, which supposedly makes them feel happier and less stressed.
The elevated body heat associated with exercise, by relaxing your muscles, may be another reason for the good feelings of exercise. Core body temperature can elevate to as high as 104 degrees during exercise and remain high for several hours after exercise ends. Some physiologists have found that exercise can have relaxing effects similar to that of sauna baths. The mechanism is relief of muscular tension through heat.
This relaxation effect is especially useful for people suffering from mental anxiety. Many drugs such as Valium work by relieving muscle tension; without muscle tension anxiety cannot be expressed. In other words, you can't be tensed and relaxed simultaneously. Studies show that exercise, by relieving built-up muscular tension, is as effective as drugs—without the side effects of drugs.
Repetitive exercise, such as running, cycling or swimming, tends to shut down the reasoning, logical side of the brain (the left hemisphere) and stimulate the creative, more abstract right half of the brain. In this way exercise stimulates both creativity and clearer thinking. The combination of a relaxed body free from tension and a clearer thinking brain allows you to deal more constructively with perplexing
Finally, exercise produces a built-in motivating effect. As you see yourself improve—whether this means less flab and more muscle or just better shape—you'll improve
For some years research has linked a high intake of dietary fat with increased risk for developing various types of cancer. One recent study shows a possible reason for this effect.
Ingesting large amounts of polyunsaturated fats, such as vegetable oils, inhibits the ability of immune factors called T- cells from ' destroying cancers. These fats also speed up tumor formation.
One cell in particular that's inhibited by a high-fat intake is the natural
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killer cell. These constitute the body's first line of defense against cancer. A high-fat intake increases production of the 2-series prostaglandins made from the fatty acid arachidonic acid, and it's these prostaglandins that directly inhibit immune function.
When you follow a low-fat diet, your body synthesizes less prostaglandin and the immune system functions more effectively to destroy cancer before it spreads. This is one of the reasons eating a lowfat diet helps to prevent cancer. (Am J Clin Nutt- 50:861- 867 , 1989)