For November 17, 2019
- Lighter training regimens best for immune system
Lighter training regimens best for immune system
NEW YORK (Reuters Health) -- Aerobic exercise three times per week may be of greater benefit to the immune system than heavier regimens of five or more times per week, researchers report.
"From the viewpoint of immune function, the optimal training regimen is of low volume," reports Dr. Roy Shephard and colleagues at the University of Toronto in Canada. Their findings are published in a recent issue of the Journal of Sports Medicine and Physical Fitness.
Previous research has suggested that an excess of athletic activity can actually depress immune function. "According to this viewpoint, light training is supposed to enhance the immune response," the Canadian researchers explain, "but larger volumes of training have a depressant effect, leaving the individual temporarily more vulnerable to viral infections."
The investigators asked 33 healthy but generally inactive men between 19 to 29 years of age to take part in one of two 12-week exercise programs -- 40 minutes of aerobic exercise (jogging or cycling) performed either 3 or 5 days per week.
Blood tests taken before, during, and soon after exercise revealed that levels of "killer" CD16 cells rose by 27% in the light training group (3 days/week) compared with just 21% in the moderate-training (5 days/week) group.
Levels of antibody-producing immune B cells dropped by 33% after moderate training, the researchers add, while light training "had no effect on B cell count."
The investigators conclude that for "the sedentary young adult, it does appear that any (immune-) protective advantage of physical activity can be obtained from a light training programme."
Moderate training did have benefits unrelated to immune function, however. The authors note that only those involved in the moderate exercise program lost weight and fat over the 12-week period. Overweight and obesity have long been associated with an increased risk for developing cardiovascular disease and diabetes.
Source: Journal of Sports Medicine and Physical Fitness 1999;39:1-11.
Bone is a dynamic tissue. It breaks down and re-builds itself constantly. As we age, the re-building process falls behind the breaking down process, resulting in weak, porous bones that are more prone to breaking.
Osteoporosis is a condition, not a disease, in which the calcium content of the bone has depleted sufficiently enough over time that the bones become brittle, porous and are likely to fracture from even minimal trauma. There are no symptoms of osteoporosis until a fracture occurs, indicating the condition is in the advanced stages with little likelihood of successful treatment.
More than 20 million Americans are affected by osteoporosis--a condition most of us believe is "for women only." In fact, twenty percent of the people who fall victim to this often debilitating condition are men. Their bone loss typically begins in their mid to late 40's and increases to a 10% loss by the age of 75. If it continues, this bone loss is classified as osteoporosis.
Many health specialists believe about half of bone loss is determined by lifestyle factors. Whether you are a man or woman there are useful steps you can take to prevent osteoporosis. This includes drinking 2 to 3 servings of calcium containing milk products or supplementing the diet with 800 to 1000 milligrams of calcium, drinking alcohol in moderation, abstaining from tobacco use, and participating in weight-bearing exercise on a regular basis.
- Beta-carotene may lower prostate cancer risk
Beta-carotene may lower prostate cancer risk
NEW YORK (Reuters Health) -- Beta-carotene, a plant product converted by the body to vitamin A, may lower the risk of prostate cancer in men whose natural blood levels of beta-carotene are low.
Beta-carotene is a natural antioxidant -- a chemical that fosters the breakdown of harmful products in the body called free radicals. It is found in high amounts in sweet potatoes, spinach, and carrots.
In the largest study of its kind, Dr. Nancy Cook and associates, from Harvard Medical School in Boston, Massachusetts, reviewed data on 3,643 male physicians, of whom 631 had been diagnosed with prostate cancer and 808 had been diagnosed with other cancers.
They found that men with the lowest blood levels of beta-carotene were 45% more likely to develop prostate cancer than men with the highest baseline beta-carotene levels.
When men with the lowest beta-carotene levels took 50 milligrams of beta-carotene every other day, their risk of prostate cancer was reduced by 32%, according to the report in the November 1st issue of Cancer.
Beta-carotene supplementation had no significant effect on the risk of other cancers, regardless of initial beta-carotene blood level, the investigators note.
Cook and colleagues add that in previous studies the link between beta-carotene and prostate cancer was inconclusive. Further research is necessary, they conclude, "to allow more definitive results to emerge."
Source: Cancer 1999;86:1783-1792.
- Ergogenic Effects Of Creatine
Ergogenic Effects Of Creatine
By ELSEVIER, PARIS
Objectives. - In the last few years many athletes and persons engaged in recreational sports activities have begun using creatine supplementation. Creatine feeding is possible by oral administration of creatine monohydrate. The objectives of this paper are to recall the mechanisms by which creatine might improve performance, to discuss the known effects of creatine supplementation on exercise performance, and to examine its side effects.
Topics. - The rate of turnover of creatine for a 70 kg male has been estimated around 2 g/d. Creatine is partly supplied by the diet that provides I g/d through meat and fish. Recent studies have shown that ingestion of about 20 g of creatine monohydrate per day is able to modulate total muscle creatine, free creatine and phosphocreatine. The aim of this article is to provide an overview of recent knowledge on the effects of creatine supplementation on exercise performance. Many studies demonstrate that creatine supplementation has beneficial effects on performance of short-duration exercises, during repeated isokinetic or isometric contractions of the quadriceps muscle, jumping or high-intensity cycling exercises. The beneficial effects of creatine supplementation on performance capacity are strongly related to the efficacy of the treatment for enhancing muscle creatine pool. If is thus clear that phosphocreatine stores play a key role for ATP resynthesis during muscle contraction and recovery. The improvement in performance following creatine supplementation is dependent on the characteristics of the exercise. It has been suggested that human skeletal muscles have an upper limit for total creatine concentration. In contrast with sedentary subjects, in athletes and well-trained subjects who have high initial total creatine concentrations in skeletal muscle, only a slight improvement in exercise performances is expected. Taken together, the results of most studies published to date suggest that only performances of repetitive high-intensity exercise bouts are positively affected by creatine supplementation. During this type of exercise, the expected increase in total creatine contributes to the fast resynthesis of phosphocreatine during recovery. Until recently, it was well accepted that except for a slight increase in body weight, no adverse effects have been associated with creatine supplementation. However, a recent report described a clinical case of renal dysfunction that was associated with oral creatine supplementation.
- Exercise guards against physical effects of stress article
Exercise guards against physical effects of stress article
NEW YORK (Reuters Health) -- Long known to help stave off heart disease, stroke and some types of cancer, regular exercise can also help protect against the physical effects of daily stress, according to a report in the November issue of the Annals of Behavioral Medicine.
In the study of 135 college students, those who exercised on a regular basis were more likely to take life's daily stresses in stride, compared with their less physically active counterparts.
Previous studies have shown that mental stress takes a toll on physical health, causing such problems as increases in blood sugar levels among diabetics, worsening of joint pain in people with arthritis, and symptoms of psychological distress such as anxiety and depression.
Study participants filled out questionnaires assessing the daily hassles they encountered during the past week -- such as car trouble, running late for appointments, or arguments with co-workers -- as well as questionnaires on major life events, mood, physical activity, and overall health.
"Minor, everyday stress contributes to the development and exacerbation of physical and mental health problems, However, people experiencing minor stress develop different degrees of symptoms, depending on their level of physical activity," explained lead researcher Dr. Cindy L. Carmack of the University of Texas M.D Anderson Cancer Center in Houston, in a written press release.
During periods of high stress, those who reported exercising less frequently had 37% more physical symptoms than their counterparts who exercised more often. In addition, highly stressed students who engage in less exercise report 21% more anxiety than students who exercise more frequently, the investigators add.
Exercise helps people get their mind off of stressors -- "providing a time-out period." This "allows for a temporary escape from the pressure of stressors and thus acts as a kind of 'rejuvenation' process," Carmack and colleagues conclude.
Source: Annals of Behavioral Medicine November 1999.
- Iron Supplementation In Athletes - Current Recommendations
Iron Supplementation In Athletes - Current Recommendations
There is still debate in the literature on whether or not endurance athletes tend to have low iron stores. In this article, we propose that endurance athletes really are at risk of becoming iron deficient due to an imbalance between absorption of dietary iron and exercise- induced iron loss. The purpose of this article is to present a critical review of the literature on iron supplementation in sport. The effect of iron deficiency on performance, its diagnosis and suggestions for treatment are also discussed.
Studies of the nutritional status of athletes in various disciplines have shown that male, but not female, athletes clearly achieve the recommended dietary intake of iron (10 to 15 mg/day). This reflects the situation in the general population, with menstruating women beings the main risk group for mild iron deficiency, even in developed countries. Whereas the benefit of iron supplementation in athletes with iron deficiency anaemia is well established, this is apparently not true for non- anaemic athletes who have exhausted iron stores alone (prelatent iron deficiency); most of the studies in the literature show no significant changes due to supplementation in the physical capacity of athletes with prelatent iron deficiency. However, the treatment protocols used in some of these studies do not meet the general recommendations for the optimal clinical management of iron deficiency, that is, with respect to adequate daily dosage, mode of administration and treatment period. For future studies, we recommend a prolonged treatment period (greater than or equal to 3 months) with standardised conditions of administration (use of a pharmaceutical iron preparation with known high bioavailability and a dosage of ferrous (Fe++) iron 100 mg/day, taken on an empty stomach).
We believe that there are sufficient arguments to support controlled iron supplementation in all athletes with low serum ferritin levels. Firstly, the development of iron deficiency is prevented. Secondly, the nonspecific upregulation of intestinal metal ion absorption is reverted to normal, thus limiting the hyperabsorption of potentially toxic lead and cadmium even in individuals with mild iron deficiency.
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