For August 15, 2018
Dehydration is what happens to your body when it loses more fluid than it takes in. Water is essential to life. It is the medium in which all the functions of our body take place. In fact, water makes up 45%-65% of our total body weight. About 62% of this water is stored in our cells. The remainder is in plasma, lymph, and other fluids.
The amount of fluid in our body usually remains relatively stable. If, for some reason fluid output exceeds fluid intake it's no problem--if the imbalance is adjusted pretty quickly. It's when fluids aren't replaced that you can get in trouble and experience dehydration. If you do, the effects can be significant. Common symptoms of even mild dehydration include muscle weakness, decreased performance, reduced cardiac function during exercise, higher resting heart rate, decreased oxygen consumption and fatigue.
It's normal for us to lose body fluids through perspiration, sweating, excretion and exhalation. Abnormal water loss occurs with prolonged vomiting or diarrhea, bleeding, burns and some medical conditions like diabetes.
The best way to prevent dehydration is to drink water regularly. Typical needs are about 6 to 8 glasses of liquid a day, but individual needs vary based on the kinds of food you eat and whether or not you exercise. If you're exercising you need more water to replace fluids lost as your body regulates its internal thermometer through perspiration. Out and out sweating does not cool your body so the requirement for water on very hot days increases significantly.
Physiologically it's smart to drink one or two glasses of water 10 to 20 minutes before exercising followed by an additional glass of water for every 20 minutes you work out. If you exercise in very humid conditions you need twice as much.
Water with glucose and electrolytes or sports drinks with polymerized carbohydrates are popular fluid replacements for people who exercise for long periods of time. The polymerized drinks speed the replacement process while providing the carbohydrates for energy.
Plain water remains the best fluid for hydrating the body.
- Dehydration Worsens Exercise-Induced Asthma
Dehydration Worsens Exercise-Induced Asthma
NEW YORK (Reuters Health)--With the return of hot weather, a word of warning to people with asthma: Dehydration can cause bronchospasm, a constriction or "tightening" of lung airways. And dehydration can make asthma brought on by exercise worse, report researchers.
Lead investigator Paula Maxwell of the University of Buffalo, New York, and colleagues compared airway reactivity after 6 minutes of high-intensity exercise in eight young adults with exercise-induced asthma and eight without the condition. Subjects first exercised when fully hydrated and again after 24 hours of voluntary water deprivation.
Hydration status had no effect on lung function in normal subjects, but the study showed that in individuals with exercise-induced asthma, dehydration resulted in a significant decrease in FEV1, a measure of lung function based on the amount of air blown out in one second.
This decline in lung function was evident both before and after exercise in these individuals, the research team reported Friday at the American College of Sports Medicine meeting in Seattle, Washington.
The investigators also noted that the rate of decline in lung function was the same in asthmatics whether they were hydrated or dehydrated, but when dehydrated, asthmatics start out with worse lung function than usual, and therefore experience more breathing problems than when they have enough water on board.
"Asthmatics are more sensitive than non-asthmatics to dehydration, but we need to investigate this condition further to determine how it affects (lung) function," said study co-author Dr. Frank Cerny, associate professor and chair of the University of Buffalo department of physical therapy, exercise, and nutrition sciences.
"The message continues to be, 'Drink fluids whenever you get the chance,'" he added. "If you have asthma, dehydration may make it worse, particularly during exercise."
Source: Journal of the American Geriatrics Society 1999;47:639-646, 755-756.
- Stretch longer for better flexibility
Stretch longer for better flexibility
NEW YORK (Reuters Health) -- When it comes to working out, holding a stretch for 15 seconds appears to improve flexibility more than holding a stretch for just 5 seconds, results of a study suggest.
The finding, from a study of 24 college students with an average age of 20, is published in the British Journal of Sports Medicine.
"Recommendations for duration of stretching in flexibility training programmes range from 5 to 60 seconds, yet justifications for these selections have largely been absent," report Jennifer M. Roberts and Karen Wilson, of the University of Sunderland, UK.
In the study, the students were split into three groups and during a 5-week period participated in a program in which they stretched for 5 seconds, 15 seconds, or did no stretching at all. Those in the 5 second group performed each stretch nine times and those in the 15 second group did the stretches three times, so that both groups had a total stretch time of 45 seconds.
Both groups showed improvements in passive range of motion -- the ability to stretch in response to an external force, such as a coach pushing on a limb. However, those who stretched for 15 seconds had a clear advantage over their peers when it came to increasing their active range of motion -- their ability to stretch their own muscles.
"This study indicates that a 5-week active stretching programme significantly increases active and passive range of motion in the (leg)," the authors conclude. "Stretching for a duration of 15 seconds produces significantly greater improvement in active range of motion than stretching for 5 seconds."
Source: British Journal of Sports Medicine 1999;33:259-263.
- Study Gives Overweight Adults Hope For Health
Study Gives Overweight Adults Hope For Health
For years, being overweight was among the worst health stigmas � and with good reason. To be obese � medically classified as being at least 20 percent above your �ideal� body weight � was associated with a lack of self-discipline, as well as an increased risk of heart disease, stroke, diabetes and some types of cancer. It was considered �common knowledge� that extra poundage � plain and simple � would always lead to an early grave.
But does it?While being overweight is certainly a health risk, a recent study suggests that the odds of dying of cardiovascular disease may be linked more closely to fitness than to fatness. In the March 1999 issue of The American Journal of Clinical Nutrition, researchers report that overweight men who were physically fit (as measured by performance on a treadmill) were less likely to die of all causes, including heart disease, than men who were lean but unfit. �Overall, it�s better to be lean than to be fat, because fatness is still an independent risk factor for cardiac disease as well as many other diseases,� says Kerry J. Stewart, Ed.D., an associate professor of medicine at Johns Hopkins and director of cardiac rehabilitation and prevention at its Bayview Medical Center. �But among those who are fat, the handful who are fit seem to have a good degree of protection from death from various causes.� Specifically, the study followed nearly 22,000 men aged 30 to 83 years for an average of eight years. They were broadly categorized by cardiovascular fitness level (fit or unfit) and body weight (lean, normal or obese). Regardless of their body weight, those who were fit had lower death rates. In fact, unfit lean men had more than twice the risk of dying of all causes than obese men who were physically fit. The results of this study are encouraging for those who exercise regularly and achieve fitness, but are still overweight. Although body weight is determined mainly by how much you eat and exercise, genetics can play a part. Some people will never be thin, even if they exercise daily. Nevertheless, these people will still be better off in terms of better health, a better quality of life and a lowered risk of death.
- Exercise Can Ward Off Gallstones
Exercise Can Ward Off Gallstones
Study Offers More Reason to Get Fit
(MSNBC News Services, September 8 1999) � Exercise isn�t just good for the heart � your gallbladder will thank you, too. Women who exercise two to three hours a week cut their risk of excruciatingly painful gallstones by nearly one-third compared with women who don�t exercise at all, according to a study at the Harvard School of Public Health.
THE USUAL treatment for painful gallstones is removal of the gallbladder, and about 500,000 Americans, two-thirds of them women, have their gallbladders taken out each year. The operations and hospitalization cost more than $5 billion a year, and the problem is the most common and costly digestive disease requiring hospitalization, according to the National Institutes of Health.
An earlier study by the same group looked only at men, even though women are twice as likely to develop gallstones. This study, published in Thursday�s New England Journal of Medicine, confirmed the earlier findings.
The researchers, led by Dr. Michael F. Leitzmann, looked at 60,290 women who were ages 40 to 65 in 1986 and had no history of gallstone disease. The women filled in surveys every two years about their activity. Overall, women who exercised about 30 minutes a day cut their risk of gallbladder surgery by 31 percent.
Obesity increases the risk of gallstones, as does rapid weight loss. But even after the researchers took obesity and recent weight changes into account, the exercisers were still 20 percent less likely to undergo gallbladder surgery.
The researchers theorize that exercise may reduce the cholesterol content of bile, the digestive juice stored in the gallbladder. That could reduce the number of gallstones, since 80 percent of the gallstones in this country are solid cholesterol. Also, people who exercise have more active large intestines and better levels of blood sugar and insulin, all of which may reduce the risk of gallstones.
Women who sit for 41 to 60 hours a week � that�s most women with desk jobs � were found to be 42 percent more likely to need their gallbladders removed than those who spend six hours or less sitting down. At more than 60 hours a week, the risk skyrockets: A woman is 132 times as likely to need gall bladder surgery as someone who spends most of her waking hours on her feet.
�I think many diseases that are problems for us in the United States are lifestyle-oriented,� said Dr. Joe Hines, a professor at UCLA Medical School. �I think this is another study which points out the importance of Americans being more physically active.�
Dr. Rudra Rai, a professor of gastroenterology at Johns Hopkins University, said the results aren�t surprising, but the study was the first he has seen to sort the effects of exercise out from a vast array of other factors, such as weight, age, hormone replacement therapy, diabetes, smoking, alcohol and caffeine.
1999 Associated Press. All rights reserved.
- Great Weight-Loss Expectations
Great Weight-Loss Expectations
(MSNBC News Services, September 10 1999) � �It just isn�t working,� you say, and you give up on an important diet or exercise resolution. It�s tempting to toss in the towel when you don�t get results fast enough. One way to overcome this temptation is to develop healthy habits that don�t feel like torture. Equally important, however, is to have realistic expectations in the first place.
STUDIES SHOW that exercise is one of the main influences on long-term weight control. But for most people, exercise works slowly. For someone who has been a �couch potato� for a number of years to start a walking program is a big accomplishment. Yet each pound of fat loss requires burning an extra 3,500 calories more than are taken in. Research shows that a person who weighs 180 pounds and walks three days a week for 30 minutes at a medium-paced three miles per hour would take almost four months to lose a pound. Someone hoping to lose a few pounds a week would have given up long before that.
Exercise can produce greater results. The acronym FIT � for Frequency, Intensity and Time � tells you how to increase the benefits. Instead of walking three days each week, which is considered the minimum for maintaining your current level of fitness, walking five or six days a week will allow the calorie-burning to add up more quickly. Or once you�ve conditioned yourself to walking three miles per hour, you can increase that to a brisk four miles per hour and burn about an extra 50 calories a session. Interval training, in which you periodically push a bit harder, is a great way to burn more calories and increase your level of fitness. Or, if you can manage an hour instead of just a half hour of walking, you double the calories you burn. The hour can be broken up and spread through the day.
Studies show that even by combining these strategies, it would take you five to six weeks to lose a pound. Your average weight loss would be eight to 10 pounds per year. This is plenty to improve fitness and gradually reduce your weight, but if you feel a need to lose weight a little faster, add some other strategies.
Weight-training exercise to increase muscle is one way to burn more calories. Muscle tissue burns more calories than does body fat. In studies of weight-training programs, in about 12 weeks people who add three pounds of muscle (while losing fat) can burn an extra 120 to 200 calories per day.
Look at your eating habits, too. By cutting back on portions or skipping a snack that was purely habit, many people can easily eliminate 200 extra calories a day without going hungry at all. That 200 calories daily can mean loss of almost half a pound a week.
By combining these strategies, weight loss can proceed at the rate of a half to one pound per week. This is the rate experts recommend to safely lose mainly fat tissue, without loss of muscle tissue or slowing down metabolic rate. A year from now you�ll be a lot better off than the people who spend the year stopping and starting less sensible exercise and diet resolutions.
These types of exercise and eating changes have been shown in many studies to produce a wide range of other benefits long before weight loss stacks up. You�ll find it easier to carry things and climb stairs. You�ll have more energy and feel less stressed. Notice and celebrate these and other changes in how you feel, and the temptation to forsake your resolutions will simply fade away.
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