For July 28, 2017
- How Your Body Responds To Exercise
How Your Body Responds To ExerciseWhen you lace up your exercise shoes and head out the door for your morning walk � or push off from the wall of your favorite swimming pool � you're responding to the orders of your conscious brain to move your muscles in a more vigorous way. As soon as those movements begin, however, a number of rapid, automatic changes also occur throughout your body. Your working muscles immediately start to burn more energy to fuel their contractions. They do this by stepping up the conversion of oxygen and nutrients into ATP (the fuel that all cells run on) inside each individual muscle cell. During sustained, aerobic activity, like a brisk walk or steady running, your working muscles might use 15 to 25 times more energy than they do at rest � burning carbohydrates and stored fat in about a 50-50 mix. During an intense, short anaerobic effort, such as running a 100-yard dash or sprinting the length of the swimming pool, your muscles may require up to 120 times more energy than at rest! Your heart immediately begins to beat faster in order to pump more blood to your muscles and other body tissues. During vigorous exercise, your heartbeat may rise to 150 beats per minute or more (compared with 70 or 80 heartbeats per minute at rest, for the average person). Why this happens: As soon you start a physical activity, nerve receptors in your blood vessels, muscles and joints signal your sympathetic nervous system to release epinephrine (adrenaline) and norepinephrine (noradrenaline) into your bloodstream. These quickly act to speed up your heartbeat. The brain's cortex also contributes to this speeding up � in fact, scientists have found that people's heartbeats begin to beat faster even before they start to exercise, as the brain anticipates what's about to happen. Whereas the average heart pumps about five liters of blood per minute at rest, the amount may increase to 20 liters per minute during vigorous exercise. (The hearts of trained endurance athletes have been measured to pump as much as 40 liters in a minute!)Your blood vessels also go through rapid changes when you start exercising. Stimulated by nerve and chemical signals, the walls of the arteries leading to your working muscles relax, causing the arteries to widen. At the same time, peripheral veins constrict, forcing more blood into your central circulation. The smaller arterioles leading to your muscle fibers also widen, and millions of dormant capillaries (which feed blood directly to the fibers) open up. (At rest, only about one in every 30 capillaries is open.) The result of all these changes is a vastly increased flow of blood (along with the all-important oxygen and nutrients it carries) to your exercising muscles � including your heart muscle, which receives several times more blood flow than it does at rest. This blood flow is maximized when each muscle relaxes, and then stops as it contracts, creating a "milking" action that helps pump blood throughout your body as you move. Increased blood flow to the skin during light and moderate exercise provides an enhanced cooling effect (you'll start sweating more heavily, as well). Meanwhile, blood flow is temporarily shunted away from the kidneys, liver, digestive system and other organs not directly involved in exercise. Your lungs also begin breathing faster and more deeply, supplying your body with more oxygen. This response results from a wide array of stimuli, including a rise in blood carbon dioxide (the by-product of utilizing more oxygen), increased body temperature and messages sent from chemoreceptors in your body's periphery. At rest, about 12 pints of air pass in and out of the average person's lungs every minute. During vigorous exercise, this rate may increase to as much as 200 pints per minute. Your metabolic rate,which depends on how many calories you're burning, goes up anywhere from four to 20 times your resting metabolic rate, depending on how hard you exercise.
- Sports Bras: Getting Some Visibility
Sports Bras: Getting Some Visibility
You probably know that sports bras have become highly visible lately.
This is because Brandi Chastain, exuberant over making the winning kick for the United States recently in women�s World Cup soccer competition, tore off her blouse and exposed a black sports bra.
It turns out that Chastain helped design the $40 sports bra, which all the women on the USA team wear. Apparently, this has resulted in a lot of interest in the specially-designed bras that give firm support to reduce bouncing of the breasts while running.
As more women become more serious about exercising, manufacturers are appealing to them by pointing out that properly fitted bras for exercising can control breast motion, feel comfortable and look good.
And there are some other issues involved. Without motion-controlling support, some women start lactating when engaged in strenuous exercise. Nipple irritation can occur using flimsy leotards for support.
And, of course, if women are more comfortable while they exercise, they are probably going to exercise more often.
In one of the few studies I�ve seen on the subject, 27 women marathon runners were mostly pleased with wearing commercial bras, although they did report some chafing.
But its questionable how much this trend has caught on. Among women athletes at the University of Washington, only 10 percent reported wearing a sports bra, according to a report in The Physician and Sportsmedicine.
I would say this is a choice best left up to the woman involved, since some sports are more rigorous than others. In volleyball, for example, some players wear front-latched bras to prevent scratches or pain from repeated diving and rolling on the floor.
There is some evidence that breast injuries can be avoided by strong support, including wrapping elastic bandages around the breasts.
Use your best judgement here. A blend of comfort, support and style would make the most sense � especially if you tend to rip your blouse off when winning a contest.
Source: The Physician and Sportsmedicine, Vol. 10, No. 11.
- Supplement Review: Pyruvate
Supplement Review: Pyruvate
Pyruvate is a chemical product of sugar metabolism. A company called Med-Pro Industries owns the patent on pyruvate (does anyone else find the trend of pharmaceutical and supplement companies actually patenting naturally occurring substances disturbing?). Med-Pro licenses out the use of pyruvate to a handful of companies, most notably Twinlab who produce, you guessed it, "Pyruvate Fuel."
Pyruvate is marketed, overmarketed if you ask me, as a dietary supplement with claims that it will increase fat and weight loss. This is reportedly accomplished through an increase in metabolic rate, brought on by supplementing with pyruvate, and a coinciding increase in fat utilization.
While I would agree with those commentators (like Bill) who have called for more research to be done on pyruvate before such bold claims are put forward, I would actually go a step further and advise you to be very skeptical about this supplement. Here's why:
The hype being pushed by the makers and distributors of pyruvate are based on claims that stem from some very dubious studies.
The main human study that pyruvate's fat and weight loss claims are derived from has significant limitations. First, the studies exclusively involved women classified as morbidly obese who were isolated in hospital wards for 3 weeks, virtually confined to their beds, and on a liquid only diet.
While the group taking pyruvate (in very large doses I might add, about 10 times the daily dose people using the supplement get) did lose 48% more fat than the group not taking pyruvate, that 48% was only less than 3 pounds of actual weight (2.86). Remember, these were extremely obese individuals on a liquid diet, not people who are training on a regular basis.
I find the other marketing claims associated with pyruvate to be equally misleading. All in all, I just don't like the way the makers and marketers of pyruvate distort the very limited and inconclusive research that has been done on the product; I'm offended by it.
And to make matters worse, pyruvate is pushed particularly hard on the web and via email marketing. Fitness and the Web are two key elements of my life and my business, so I get a little peeved about things like this. There are a handful of good supplements available that will help you to drop those extra pounds and promote fat loss. I'm convinced that pyruvate is not one of them.
- The Role Of Pyruvate In Weight Loss
The Role Of Pyruvate In Weight Loss
By DENNIS R. SPARKMAN, PH.D.
Pyruvate is the last metabolite in the breakdown of glucose (glycolysis). In the past several years it has become available as a dietary supplement and nine well-controlled human studies have not only demonstrated that it is a safe dietary supplement, but that it has a host of functions that are beneficial to the human body. Among these are enhanced weight loss and fat loss, reduced weight and fat regain following a calorie restricted diet, increased exercise endurance, decreased perceived exertion. The problem with these studies was that they used pyruvate in amounts that ranged from 31 to 100 grams per day, which are impractical outside of a research setting. Now a study has looked at what the minimum amount of pyruvate that is necessary to achieve these results.
Fifty-three individuals took part in a study where one group took 6 grams of pyruvate per day for six weeks and two other groups took either a placebo or nothing, respectively. Each group exercised for 30 minutes five times per week. Although there was no change in their absolute bodyweight, those who supplemented with pyruvate had a 12% decrease in percent bodyfat, lost 4.8 pounds of fat, gained 3.4 pounds of muscle, and had a 2.2% increase in basal metabolic rates. Additionally, they reported a 17.7% increase in vigor and 71% decrease in fatigue.
According to previous studies in animals, scientists have been able to estimate that the minimum effective daily dose of pyruvate in humans is between three and six grams. Although the six grams per day used in this study is far less that the amounts used in previous studies, it is effective in helping to reduce bodyfat, increase lean muscle mass, as well as increasing vigor and decreasing fatigue during exercise.
Colker C, Stark R, Kaiman D, et al. The effects of a pyruvate based dietary supplement on weight loss, body composition, and perceived vigor and fatigue levels in mildly overfat individuals. Am J Clin Nutr. 1997 (in press).
- Canadian study offers new evidence of exercise's benefits
Canadian study offers new evidence of exercise's benefits
September 17 -- A University of Calgary study is one of the first to indicate that fibromyalgia patients may benefit from an exercise program that includes strength training.
Published in the June 1996 issue of The Journal of Rheumatology, the study found that a short-term exercise program led to a decrease in both the number of tender points and the degree of muscle tenderness. Also, it improved aerobic fitness levels. The program combined strength training, aerobic activity, and flexibility training.
Thirty-eight subjects completed the study. Eighteen fibromyalgia patients were in the exercise group, and 20 fibromyalgia patients were in a comparison relaxation group. For six weeks, the exercise group met for an hour three times a week to participate in equal amounts of aerobic walking, flexibility training, and strength training. The comparison group met on the same schedule to participate in hour long relaxation sessions that included yoga and visualization training.
By the end of the study, the exercise group's number of tender points had decreased by an average of 2.5, and muscle tenderness had improved by about 32 percent. The exercise group did indicate more fatigue at the end of the study. Researchers attributed that finding to the sedentary lifestyle led by a majority of the group's members before participating in the study. The relaxation group inexplicably showed decreased aerobic fitness.
This short-term study supports previous findings about the benefits of exercise. Only further research can determine the long-term effects of exercise in the treatment of fibromyalgia.
As the study's authors noted any fibromyalgia patient wishing to begin an exercise program should seek out an instructor familiar with fibromyalgia who can design an appropriate individualized program.
- Fish Oil May Help Unclog Diseased Heart Arteries
Fish Oil May Help Unclog Diseased Heart Arteries
By AMY NORTON
In a fat-fearing world, fish oil is emerging as one fat even a cardiologist can love. Adding to evidence that the omega-3 fatty acid promotes heart health, German researchers have found that a daily dose of fish oil may help slow or even reverse the hardening and narrowing of arteries in patients with heart disease.
In the current issue of the Annals of Internal Medicine, researchers from the University of Munich report that a fish- oil capsule a day may ``modestly'' improve blood flow to the heart and bolster traditional therapy in patients with atherosclerosis, or hardening of the arteries.
In a study of 223 men and women, those who took a dose of fish oil per day for two years had fewer atherosclerosis complications such as heart attack and stroke. Two fish-oil patients had complications, compared with seven patients on a placebo pill that contained other fatty acids similar to those of the ``average European diet.'' Most patients were also on cholesterol- lowering drugs, and many had previously had surgery to unclog their arteries.One of the ``good,'' polyunsaturated fats, fish oil has widely been thought to have important heart benefits. Found in fish such as salmon, it is a key component of the low-saturated-fat Mediterranean diet that has been linked to the lower incidence of heart disease in that area of the world.
Just how fish oil bestows its benefits has been unclear, but researchers have suspected that it somehow helps clear clogged heart arteries. The German team, led by Dr. Clemens von Schacky, used X-rays to peer into the patients' heart arteries at the beginning and end of the study. They found that after two years, the arteries of the fish-oil patients, on average, offered more room for blood flow.
The improvements were not dramatic, however; the fish-oil capsules failed to reverse the disease course in most patients. In the fish-oil group, 14 patients did show a mild reversal of artery clogging, compared with seven in the placebo group. Two fish- oil patients showed moderate reversal, while no placebo patients did. For 35 in the fish-oil group, atherosclerosis progressed slightly, and for four, artery narrowing progressed moderately _ results that were almost identical to those of the placebo group, in which 36 worsened slightly and five showed moderate disease progression.
Still, von Schacky's team concluded that the benefits found in this study are significant enough to warrant including fish oil as part of traditional heart-disease treatment. Taking a daily capsule or dining on fish twice weekly would fulfill the prescription, according to the researchers.
Dr. Robert Vogel, a cardiologist at the University of Maryland in Baltimore, agreed that the omega-3 fatty acid, in the form of food or pill, is a wise addition to heart-disease therapy. But he pointed out that fish oil has been shown to have greater effects on factors other than atherosclerosis in treating heart-disease patients. Other research, said Vogel, has revealed that fish oil may help correct heart-rhythm disturbances and that it has a blood-thinning effect. It also appears to spur chemical changes in blood vessels that help them dilate.
``As a supplement, fish oil has fairly dramatic benefits,'' Vogel said. ``This is an area of research that has been consistent.''
Annals of Internal Medicine (1999;130:554-62)
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