Exercise, activity that results in contraction of skeletal muscle. The term is usually used in reference to any activity that promotes physical fitness. Although muscle contraction is the common element of all forms of exercise, many other organs and systems are affected, for example, the heart and lungs. Many people also find that regular exercise enhances their sense of mental well-being along with their general physical health.
Today there is an increasing emphasis on preventive medicine, or maintaining health, partly as a result of the increasing costs of health care and our greater awareness of the effects of lifestyle on health and longevity. While public interest in exercise and fitness has increased during the past 20 to 30 years, according to the United States National Center for Health Statistics, in 1990 only 41 percent of adults 18 to 64 years of age reported that they exercised regularly, and only 32 percent of those over 65 years of age reported regular exercise or participation in physical sports. Over one-quarter of Americans (three-quarters by some standards) are significantly overweight and are at risk for a wide variety of health problems.
Questions and Answers About Physical Fitness
Q: What exercises can I do to prevent or recover from back injury?Questions and Answers About Physical Fitness
A: According to the American Medical Association, four out of five adults have suffered from chronic back pain. In the past people were told to lie down and rest to deal with their back pain. But more recently we have found that such advice actually contributes to more pain and disability due to the weakening of muscles. Now doctors are advising patients to get or stay active as a way of dealing with back pain.
You should definitely add strength training to your routine, especially exercises that target the abdominal and the back muscles. Strengthening these muscle groups will likely help to alleviate some of your pain, because weak back and abdominal muscles are often contributors to chronic back problems.
Walking will not exacerbate a back problem, and it is important for overall health. Be sure to replace your exercise shoes often, as the support your shoes lend is critical. Yoga and other exercises designed to improve your flexibility have been shown to reduce risk of back injury..
Q: Is quick walking or slow jogging more effective at burning calories?
A: When you exercise, your muscles burn fuel to do their work. This fuel is measured in calories and comes from three sources: stored carbohydrates called glycogen; stored body fat found in fat cells tucked away in small droplets in the muscles; and to a much lesser amount body protein found in muscles and other lean tissue.
How many total calories you burn during your activity, as well as how much of this fuel comes from the three fuel sources, depends primarily upon three factors: the intensity of the exercise, your overall fitness level, and the duration of the activity.
During low-effort exercise, such as walking, fat is the primary fuel source, supplying about 60 to 70 percent of the calories burned; carbohydrates are the secondary source. As you increase your effort—for example, speeding up your walking pace to a run—your muscles burn more calories per minute, and a shift begins toward carbohydrates supplying more of the energy and fat supplying less. Only when you exercise for long durations at high intensity do you burn protein.
Keep in mind as you choose whether to walk or run during your workout that the best way to lose weight or maintain weight if you are at ideal body weight is to burn as many calories as possible during each workout session.
Q: How do you do crunches? Are they the same as sit-ups?
A: Crunches are a modified version of sit-ups. When doing a crunch you lift your torso slightly up and off the floor, bringing your shoulders slightly towards your hips, not all the way up to your knees as in a sit-up.
The correct technique for a crunch is as follows:
- * Lie on your back on a mat, with your knees bent and feet flat on the floor.
- * Place your feet slightly less than hip-width apart.
- * Cup your hands by your ears, keeping your elbows pointed out to the sides.
- * Keep your lower back against the floor so that you are not arching your back.
- * Contract the muscles in your abdomen to slowly lift your torso so that your shoulder blades come off the floor. Beginners may only be able come up one or two inches.
- * Support your head with your hands as you come up but avoid pulling your head forward. Your chin should be tucked in slightly.
- * Keep your eyes focused on the ceiling.
- * Take two counts to lift your torso, hold for one count, and then lower your torso back to the starting position for two counts. Exhale as you lift your torso, and inhale as you lower it.
Q: For the maximum health benefit, should I devote more exercise sessions per week to weight training or to aerobics?
A: Strength training has many benefits for health and well-being, but it doesn’t train your heart and lungs. For that essential piece of the fitness picture, you need aerobic exercise. Conversely, aerobic exercise won’t make you strong. If you are trying to stay fit by only doing aerobic exercise, the ultimate irony would be to live to an old age with a healthy heart—only to find yourself too feeble to remain independent.
It is essential to strike a good balance between strength training and aerobic exercise to make a healthier you. A good general rule of thumb is to try to get a minimum of about 20 to 30 minutes of vigorous aerobic activity three times per week and 20 to 30 minutes of strength training twice a week.
Q: What is a good way to make sure I'm exercising at a safe yet beneficial level?
A: The key to maximizing results during aerobic activity is to work out at the right intensity. The average healthy person will want to work out at 60 to 80 percent of their maximum heart rate. Maximum heart rate can be approximated by subtracting your age in years from 220. For example, a 30-year-old woman’s maximum heart rate would be 190 beats per minute. She would want to maintain a target heart rate between 114 and 152 beats per minute (bpm) during her workout, thereby staying within the 60 to 80 percent of her maximum heart rate range.
Heart rate monitors are an effective way to gauge your heart rate. Another alternative, and a less expensive one, is to take your own pulse. In addition to checking your pulse routinely throughout your workout, be aware of how you are feeling overall as you exercise. You should always be able to talk during your workout.
Q: Is it true that muscle weighs more than fat? If so, will I gain weight when I start strength training if I don’t go on a diet?
A: I am often asked whether strength training will make women gain weight or look bulky, and I’m happy to report that the answer is a resounding “NO!” Here’s why: One pound equals one pound regardless of whether the pound is fat, muscle, or some other substance such as butter or steel. Muscle is denser than fat and therefore takes up a smaller amount of space per pound than fat. Some scientists estimate that the space that one pound of muscle occupies is about 22 percent less than one pound of fat! If a woman begins strength training and eats exactly the same number of calories as she did before she began lifting weights, she may lose some weight because she is burning additional calories while exercising. Even more significant will be the change in her body composition. She will gain muscle and lose fat, even if her body weight stays the same. In my experience, most women drop a dress size or two after they have been strength training for a couple of months—because their body shape has changed for the better.
Q: What is plyometrics, and is it an effective method of exercise?
A: Plyometrics is an advanced training technique aimed at linking strength with speed of movement to produce power. To use a conceptual mathematic equation, plyometrics is strength plus velocity equals power.
Plyometric exercises teach muscles to respond quickly and powerfully. By stretching a muscle tightly and then quickly contracting it, plyometric drills enable a muscle to reach maximum strength in as short a time as possible. With plyometric training, people seek to train the body's fast-twitch muscle fibers so that they can load, or stretch, the muscle more quickly, and in turn, unload it more quickly to produce more power. In terms of basic muscular physiology, a prestretched, or loaded, muscle is capable of generating more force than an unstretched muscle.
Higher than normal forces are put on the musculoskeletal system during plyometric exercises, so it is important for the athlete to have a good, sound base of general strength and endurance. A thorough grounding in weight training is essential before you start plyometrics. It has been suggested that athletes be able to squat twice their body weight before attempting depth jumps. However, less intensive plyometric exercises can be incorporated into general circuit and weight training during the early stages of training so as to progressively condition the athlete. Simple plyometric drills, such as skipping, hopping, and bounding, should be introduced first. More demanding exercises such as flying start single-leg hops and depth jumps should be limited to thoroughly conditioned athletes.
Q: When my walking sneakers get too worn to use for walking, can I wear them when I do my non-aerobic exercise videotapes?
A: It is very important to replace your walking or running shoes frequently to maximize your training routine and minimize injuries. After your shoes are past their prime, you certainly can wear them at other times. You can wear them during your non-aerobic exercise videotapes as long as the exercises in the videotapes are done while seated or on the floor. If the exercises are standing or marching (i.e., weight bearing), then you should be using shoes that you would normally use for walking or running.
Q: Why are Spinning classes so popular? Can't I get the same benefits from riding a stationary bike on my own at home?
A: Spinning, or stationary biking, is very popular. It has skyrocketed in popularity since being introduced by Schwinn in 1995. Gyms across the country conduct Spinning classes as an alternative to other forms of aerobic exercise.
You can achieve the same benefits of riding a stationary bike at home. However, research shows that most people will likely enjoy—and therefore continue—their exercise program when done in a group setting. Also, you are more likely to work out at a higher intensity during a Spinning class, and this will help you improve your fitness level faster. Another good reason to participate in a class setting is to assure that your bike is set up properly. Remember, no exercise equipment is one size fits all.
Q: How important is stretching, and should it be done before or after exercise?
A: Stretching is an important component of any well-rounded exercise program. Stretching enhances flexibility. If you have strong, flexible joints all physical activity will be easier and more enjoyable, and you’ll be less likely to suffer injuries. Furthermore, there is new research that demonstrates that stretching between sets of strength training exercises helps gain more muscle strength from an exercise program. It is recommended that you stretch after you have warmed up a little and that you stretch after you have completed your workout. If you can only do one stretching session, however, do it either between sets of strength training exercises or at the end of the session.
Q: How can I tighten my inner thighs? What exercises do you recommend?
A: First, you need to realize that it is impossible to 'spot' reduce. This means you cannot change one specific area of your body— the inner thighs or stomach or upper arms—by doing a specific exercise like leg lifts or abdominal crunches or triceps extensions. To become more satisfied with the shape of your inner thighs you need to address your body's overall fitness level. Toned inner thighs are the result of your health, diet, body weight, and fitness as a whole.
Ask yourself the following questions as a mini-assessment: Are you currently at your healthy, ideal body weight? Are you eating a balanced diet that includes whole grains, whole foods, fruits, and vegetables? Does your fitness program include aerobic exercises such as walking for your heart and lungs, strength training for your muscles and bones, and flexibility exercises for your muscles, tendons, and ligaments?
Q: How can I assess the trainers at my gym, other than by checking their credentials?
A: It takes more than certification to make a great teacher, and the same holds true for trainers. The best trainer is one who matches your needs. The trainer I would recommend for an Olympic-caliber athlete is not the same one I’d suggest for an out-of-shape, 47-year-old woman who wants to begin training. Ask yourself the following questions in order to help you make your assessment: Has the trainer helped people like you? Does he or she understand and share your goals? Are his or her instructions easily understood? When the trainer corrects you, do you feel helped rather than criticized? Do you feel comfortable asking questions? Has the trainer adapted his or her program to fit your needs?
Q: Will I get a better workout if I wear a weighted vest or hold weights when I walk on my treadmill?
A: I do not recommend using dumbbells, wrist weights, or ankle weights when walking, as doing so increases your risk of injury. Holding weights can strain your neck and shoulders and makes it difficult to maintain correct arm movement and posture. Also, weights that are light enough to hold when walking are not heavy enough to increase your strength.
Ankle weights may cause you to trip and fall and can alter your stride, causing muscle strain. Why take the chance when there is little benefit and greater risk of injury? A weighted vest is safe to use while walking but is probably not all that beneficial.
If you are considering using weights to increase the intensity of your walking workout, we recommend that you walk at a slightly faster pace or increase the incline of your treadmill instead. You may also consider using a heart rate monitor or timing yourself to accurately measure the intensity of your walking workout. This will give you an objective way to increase your pace if you need a greater challenge.
Q: In the weight-training videos I use, there's often a short break between exercises. Should I use this time to recover, or should I do some aerobic activity, such as jogging in place?
A: The best activity to perform during the short breaks in the weight-training video is stretching exercises of the muscles that you have just been exercising. Current research is showing us that you will gain more strength and flexibility if you take the time between sets of exercises for stretching.
Q: In weight training is it more beneficial to increase the amount of weight or the number of repetitions?
A: To get the most benefit out of a strength-training program it is best to keep the repetitions from 8 to 12 for each exercise. The American College of Sports Medicine recommends that you complete 1 to 3 sets for each exercise. The most important aspect of any strength-training program is that you work out at a high enough intensity so that your muscles get enough stimulation to get stronger. You will not get bulky by following a routine that includes 6 to 12 exercises, 8 to 12 repetitions of each exercise, and 1 to 3 sets of all the exercises at a high intensity. You will gain some muscle, lose fat, and get much stronger.
Q: Why shouldn’t I make my own weights for working out?
A: I have seen suggestions ranging from lifting one-pound soup cans to lifting buckets or one-gallon jugs filled with sand. Please do not improvise! Plastic jugs and buckets are not made for strength training: They’re not designed to hold that much weight, and the handles are designed for carrying, not lifting. They could easily break and injure you. Using soup cans doesn’t pose this danger, but their light weight won’t help you build muscle.
Q: Will I get the same results if I exercise one day for 60 minutes instead of two days for 30 minutes each?
A: The current recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine is to “accumulate 30 minutes or more of moderate physical activity on most, preferably all, days of the week.” I encourage all individuals to do their best to have some physical activity on a daily basis. Physical activity is a key to long-term health and weight control.
If you have the choice between one 60-minute workout versus two 30-minute workouts, I would recommend that you choose the two 30-minute vigorous workouts spread out over the week so that you are getting some physical activity throughout the week. You will actually experience some loss in the benefits of exercising if you wait six days between workouts. In addition, you put yourself at increased risk of sports-related injuries by working out just one time per week.
Q: I've tried doing yoga but find it too slow and static. Is there a faster-paced form?
A: Yoga is one of the most ancient art forms, originating in India thousands of years ago. It is terrific exercise that reduces stress and increases both flexibility and coordination, and it improves overall health and fitness. Yoga can be practiced by anyone and can be tailored to satisfy every individual's needs.
Power Yoga, which is also known by the Sanskrit term Vinyasa Yoga, is likely the best form for those looking for the benefits of yoga without the methodical pace. A vinyasa is a series of flowing movements that warm up the body. Power Yoga is an active form of yoga, in which a person moves quickly through the poses, called asanas, not holding them as long as in other styles of yoga. It is virtually guaranteed that Power Yoga will give a real challenge to the muscles.
PHYSIOLOGY OF EXERCISE
Contraction of skeletal muscles, the muscles under conscious control, is the primary physiological event during exercise. Because skeletal muscles can actively contract, but are not designed to actively lengthen, they are arranged as opposing pairs. As one muscle shortens, another is stretched. An example of such a pair of muscles can be observed in the upper arm, where the biceps and triceps have opposite actions. To flex the arm at the elbow, the biceps contract, while the triceps stretch. To extend the forearm, the triceps contract, while the biceps lengthen.
CELLULAR CHANGES
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At the molecular level, muscle contraction occurs when large proteins called actin and myosin slide together to shorten muscle fibers. The energy for contraction and relaxation of skeletal muscle is provided by a molecule called adenosine triphosphate (ATP). ATP is a high-energy molecule formed during the breakdown of glucose (a kind of sugar) or fats. Glucose can be stored in muscle as glycogen, and enters exercising muscle from the blood.
The metabolism of glycogen or glucose to provide energy for exercise occurs in one of two ways, depending on the presence of available oxygen to the muscle, which in turn depends on the type of exercise being performed. If oxygen is not available (anaerobic activity), glycogen or glucose will be broken down by the anaerobic pathway (glycolysis). If oxygen is available (aerobic activity), it will be metabolized by the aerobic pathway (known as the Citric Acid Cycle). When oxygen is readily available, glucose reacts completely with the oxygen to produce water and carbon dioxide. A portion of the energy released from one molecule of glucose is utilized to produce ATP.
Anaerobic and Aerobic Exercise
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Pilates
Pilates is a low-impact system of exercise that improves strength, posture, and balance. The method was founded by German-born Joseph Pilates in the 1920s.
During anaerobic metabolism, the breakdown of glucose stops at an early point, producing lactic acid and two molecules of ATP. This anaerobic metabolism produces a so-called oxygen debt, which is repaid later when oxygen becomes available. When a skeletal muscle is heavily worked, the acute soreness that results is due partly to a buildup of lactic acid. The presence of lactic acid can also be felt during exercise as a burning sensation in the muscles.
Anaerobic exercise involves heavy work by a limited number of muscles, for example during weight lifting. These types of activities are maintained only for short intervals, and the supply of oxygen is insufficient for aerobic metabolism, resulting in a substantial oxygen debt and anaerobic metabolism within those muscles. Another example is sprinting, in which the exercise is high in intensity but short in duration, resulting in substantial oxygen debt. Weight lifting and other types of anaerobic exercise increase strength and muscle mass, but are of limited benefit to cardiovascular health.
Unlike anaerobic exercise, aerobic exercise uses oxygen to keep large muscle groups moving continuously at an intensity that can be maintained for at least 20 minutes. Aerobic exercise uses several major muscle groups throughout the body, resulting in greater demands on the cardiovascular and respiratory systems to supply oxygen to the working muscles. Aerobic exercise includes walking, jogging, and swimming, and is the form recommended for reducing the risk of heart disease and increasing endurance.
HEART, RESPIRATION, AND EXERCISE
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Stress Test
The stress test, also called an exercise electrocardiogram, measures the heart rate of a person during exercise and identifies any abnormal changes in heart function. Such changes may indicate the presence of coronary or arterial disease.
Although skeletal-muscle contraction is a main feature of exercise, many other systems in the body are activated to support this process. The heart pumps increased volumes of blood to supply oxygen and nutrients and remove carbon dioxide and metabolic wastes; the respiratory system handles an increased workload, exchanging oxygen and carbon dioxide between the blood and the atmosphere. The nervous system and various hormones have important roles as well, integrating the body's response to exercise and regulating the metabolic changes that occur in muscle and other tissues.
Another critical role of the cardiovascular system and respiratory system during exercise is to get rid of the heat produced by increased metabolism. During exercise, increased blood flow to the skin results in direct transfer of heat to the environment as well as loss of heat during evaporation of sweat. Substantial heat is also transferred to the atmosphere in exhaled air during breathing.
The effects of exercise on the heart and circulation can vary considerably with intensity of exercise and with physical fitness. Assessment of a person's physical fitness often includes measurement of aerobic capacity in the form of maximum oxygen consumption, or VO2 maximum, during aerobic exercise. Oxygen consumption of like-sized fit and unfit individuals will be approximately the same at rest or at a given level of exercise, for example, walking on a treadmill.
But the more fit person will be able to achieve a greater maximal oxygen consumption due to the training effect that takes place with regular aerobic exercise. As a person engages in regular aerobic exercise, the heart, lungs, and muscles all become more efficient at using oxygen. The heart pumps more blood with each stroke, the lung capacity of each inhalation increases, and the muscle fibers extract more oxygen from the blood. The training effect on the heart is quite obvious when heart rates are compared between long-distance runners and sedentary individuals. The athlete will have a lower heart rate at rest (perhaps as low as 50 beats per minute) and during light jogging, for example, than the nonathlete (who might have a resting rate of 80). During light jogging, the untrained person will experience a large increase in heart rate, while the athlete's heart rate will not rise nearly as much.
But the more fit person will be able to achieve a greater maximal oxygen consumption due to the training effect that takes place with regular aerobic exercise. As a person engages in regular aerobic exercise, the heart, lungs, and muscles all become more efficient at using oxygen. The heart pumps more blood with each stroke, the lung capacity of each inhalation increases, and the muscle fibers extract more oxygen from the blood. The training effect on the heart is quite obvious when heart rates are compared between long-distance runners and sedentary individuals. The athlete will have a lower heart rate at rest (perhaps as low as 50 beats per minute) and during light jogging, for example, than the nonathlete (who might have a resting rate of 80). During light jogging, the untrained person will experience a large increase in heart rate, while the athlete's heart rate will not rise nearly as much.
BENEFITS OF EXERCISE
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Running
Sometimes known as jogging, running became a popular fitness activity in the 1970s. The average person can derive health benefits from as little as three 20-minute running workouts a week, physiologists say.
Getty Images/Jim Cummins / FPG International, LLC
The benefits of exercise are far-reaching. Clinical and epidemiological studies have demonstrated that regular aerobic exercise reduces the risk of death due to heart disease and stroke, aids in reducing weight, helps prevent diabetes mellitus, strengthens bones, and enhances immune function. The psychological benefits are also broad, and most studies suggest a positive relationship between physical fitness and mental achievement.
The relationship between regular aerobic exercise and cardiovascular health and longevity is well established. Regular exercise leads to a reduction in the risk of coronary heart disease, in which fatty deposits (plaque) form in blood vessels supplying the muscular wall of the heart, compromising oxygen delivery to the heart muscle. In addition, with regular exercise the efficiency of the heart during exercise is increased.
Many people exercise to lose weight. A calorie is a unit that measures the energy content of foods and the energy expenditure by the body. When the daily calorie intake from food is the same as calories expended from exercise, weight remains the same. The number of calories burned during exercise varies greatly with the type of physical activity, but the key to successful weight reduction is to exercise regularly, without increasing food intake proportionally. For example, walking one hour per day may utilize only 300 calories of energy per day, a small fraction of an individual's daily caloric intake. But over a period of time, if food consumption is simultaneously reduced or remains the same, significant weight loss will result. One sound approach to reducing calories is to eat healthier foods that contain more fiber and less fat, and therefore fewer calories. This type of diet has also been proven healthier for the heart and blood vessels.
One area of controversy has been how much exercise is enough to improve general health, reduce the risk of heart disease, and increase longevity. Meaningful studies on this topic are very difficult to perform because they require large populations of subjects and many years of data collection, and because poor health sometimes results in limitations to physical activity. Despite these difficulties, it is clear that regular exercise, along with a generally healthy lifestyle, is beneficial. People who have sedentary lifestyles make up half the population of industrialized societies, and this group has the most to gain by exercising. One recent U.S. National Institutes of Health (NIH) panel suggested that as little as 30 minutes every day of purposeful, moderately strenuous physical activity—for example, rapid walking or lawn mowing—is sufficient to lower the risk of heart disease. There is no conclusive evidence to prove that an especially rigorous exercise routine, such as running many miles per day, as opposed to walking or jogging daily, will add years to a person's life.
GETTING IN SHAPE
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Aquatic Exercise
Aquatic exercises provide a workout without undue strain on the joints and muscles. Such activities are particularly helpful for older people or those who have experienced physical injury.
Physical fitness is often defined in terms of four measurements: cardiovascular-respiratory function, body composition (the proportion of lean body mass in comparison to fat), flexibility, and muscular endurance and strength. Exercise is characterized in terms of four variables as well: frequency, intensity, duration, and mode. In planning an exercise program, it is important to take into account one's personal fitness objectives and the exercise regimen that will best meet those objectives. Age and existing health conditions should also be considered. Individuals over the age of 40 or who suffer from serious health problems or physical limitations should first consult a physician for recommendations about the best exercise program to adopt.
Questions and Answers About Nutrition
Q: I’m going to college this fall to study dietetics. My ultimate goal would be to work in sports nutrition, helping train university athletes to eat properly. What advice can you give me?
A: A good education is absolutely essential, and you are beginning on the right path with a degree in dietetics. Sports nutrition is a specialty area of dietetics and requires further training beyond a bachelor’s degree. There are several options. One path is to pursue a master’s degree in a department of nutrition that has a sports emphasis. Another path is to have a dual degree in both nutrition and exercise science or exercise physiology. It is also just as important to be physically active yourself. Athletes look to other active people when seeking information. The sports nutrition practice group of the American Dietetic Association, SCAN, is a wonderful resource for anyone interested in this field. The group’s Web site offers information on career development as well as university degree programs in sports nutrition.
Q: What are the physiological consequences of eating disorders such as anorexia nervosa and bulimia?
A: The physiological signs and symptoms of anorexia nervosa include the following:
* Significant weight loss * Recurrent overuse injuries and stress fractures * Cold hands and feet and extreme sensitivity to cold temperatures * Lightheadedness * Inability to concentrate * Hyperactivity * Compulsive exercise beyond normal training * Dehydration * Electrolyte imbalance * Irregular heartbeat and cardiac arrest
* Significant weight loss * Recurrent overuse injuries and stress fractures * Cold hands and feet and extreme sensitivity to cold temperatures * Lightheadedness * Inability to concentrate * Hyperactivity * Compulsive exercise beyond normal training * Dehydration * Electrolyte imbalance * Irregular heartbeat and cardiac arrest
From Mental Health Net: “Profound physical symptoms also occur in cases of extreme starvation. These include loss of head hair, growth of fine body hair, constipation, intolerance of cold temperatures and low pulse rate. Certain endocrine functions also become impaired. In females this results in a cessation of menstruation (amenorrhea) and the absence of ovulation. Menstruation usually will not resume until endocrine balance is restored. Ovulation is suppressed because production of certain necessary hormones decreases. Anorexia in boys has effects similar to those in girls: severe weight loss, psycho-social problems and interruption of normal reproductive system processes.”
The physiological signs and symptoms of bulimia include the following:
* Weakness, headaches, dizziness * Frequent weight fluctuations * Difficulty swallowing and retaining food * Bloodshot eyes
* Weakness, headaches, dizziness * Frequent weight fluctuations * Difficulty swallowing and retaining food * Bloodshot eyes
From MamasHealth.com:
* Erosion of tooth enamel because of repeated exposure to acidic gastric contents * Dental cavities, and sensitivity to hot or cold food * Swelling and soreness in the salivary glands (from repeated vomiting) * Stomach ulcers * Ruptures of the stomach and esophagus * Abnormal buildup of fluid in the intestines * Disruption in the normal bowel release function * Electrolyte imbalance * Dehydration * Irregular heartbeat and in severe cases heart attack * A greater risk for suicidal behavior * Decrease in libido
* Erosion of tooth enamel because of repeated exposure to acidic gastric contents * Dental cavities, and sensitivity to hot or cold food * Swelling and soreness in the salivary glands (from repeated vomiting) * Stomach ulcers * Ruptures of the stomach and esophagus * Abnormal buildup of fluid in the intestines * Disruption in the normal bowel release function * Electrolyte imbalance * Dehydration * Irregular heartbeat and in severe cases heart attack * A greater risk for suicidal behavior * Decrease in libido
Q: What are basal metabolic rate and resting metabolic rate?
A: The basal metabolic rate and resting metabolic rate both measure the energy required to maintain the systems of the body and to regulate body temperature at rest. The differences are usually based on research settings.
Basal metabolic rate (BMR) is usually measured after the subject has stayed overnight in a metabolic chamber or research ward and has not eaten in the last 12 hours.
Resting metabolic rate (RMR) usually means the subject slept at home and drove or was driven to the research lab for testing, but still followed a 12-hour fast.
These usually differ by less than 10 percent. RMR usually accounts for 60 to 80 percent of total daily energy expenditure in most sedentary adults. This percentage will vary greatly in active individuals.
Q: What are the best ways to measure body fat?
A: There are a number of different ways to measure body fat, each with pros and cons, depending on your circumstances.
Underwater (hydrostatic) weighing
Known as the gold standard, this method is generally done in a health-care or research setting and is not widely available to the public. It requires the subject/patient to expel the breath and then hold like this under water so that an accurate underwater body density can be measured. The results are highly reliable, but this may be a difficult procedure for some individuals.
Skinfold measures
This is a very technique-sensitive method, and results vary from operator to operator. Consistency is dependent on the skill of the operator. There can be a 2 to 4 percent standard deviation, and this can easily be much greater depending on the skill of the operator. This method is commonly available to the public through dietitians and personal trainers.
Bioelectrical Impedance Analysis (BIA)
Commonly found at health clubs, gyms, and health-care offices, BIA is a relatively new body-composition analysis technique and is highly dependent on hydration levels. BIA results are often very similar to those of skinfold analysis. For consistent and accurate results, measurement conditions should be as consistent as possible:
Do not consume alcohol within 48 hours prior to test
Avoid intense exercise 12 hours before test
Avoid eating or drinking (especially products containing caffeine) 4 hours before the test
Empty bladder 30 minutes before the test. Avoid all diuretics for 7 days before test (if possible)
Measure in bare feet
Measure 3 hours after waking
Dual-Energy X-Ray Absorptiometry (DXA)
Available only at major medical centers, DXA assesses regional and total bone mineral content as well as regional and total fat and fat-free content of soft body tissues. Promising research has validated DXA as an approach for assessing body composition.
Q: What is body mass index?
A: Body mass index (BMI) is a mathematical ratio of height to weight that can be linked with body composition (or body fat percentage) and with indices of health risk. People with a BMI of 25 to 29.9 are considered overweight, and people with a BMI of 30 or above are considered obese. A high BMI assumes a higher percentage of body fat, which places a person at greater risk for developing chronic diseases such as diabetes mellitus, hypertension, heart disease, and even cancer.
However, for some people the BMI is not a reliable indication of health. A highly muscled individual who is very fit and healthy may have a somewhat heavy body weight because muscles pack on a lot of pounds. This person may have a high BMI that improperly puts him or her in the overweight or obese categories. Likewise, thin individuals who have a low body weight with very little muscle and a higher percentage of fat may have a normal BMI, which would be an incorrect indication of healthiness.
Q: Can caffeine enhance athletic performance?
A: This depends on the user. Caffeine will certainly hurt the athletic performance of individuals who are sensitive to the effects of caffeine. So if you get “caffeine jitters,” don’t use it. Caffeine is also a mild diuretic. If you are not well hydrated to begin with, caffeine may exacerbate your dehydration, which will hurt performance. Caffeine is also a natural cathartic, so if you are getting ready to compete in a long race and are sensitive to this effect of caffeine, it may not be very helpful, either.
Caffeine is the most widely used drug in the world. In the athletic world caffeine has been touted as an energy-promoting and fat-burning aid. In athletic competition, caffeine is a “controlled or restricted drug” and is banned by the International Olympic Committee if urine levels exceed allowable limits. It is also banned by the NCAA in amounts that exceed urine levels of 12 micrograms of caffeine per milliliter of urine.
Numerous research studies have examined the influence of caffeine on athletic performance. The results are not crystal clear, but laboratory studies have shown that moderate doses of caffeine (3 to 9 milligrams per kilogram of body weight) at least one hour prior to exercise can enhance exercise performance. (A typical 5 to 6 ounce cup of brewed coffee contains approximately 100 milligrams of caffeine.)
Note that the research has shown positive impacts on performance primarily when the subjects have been trained athletes who habitually use caffeine. The majority of this research has been done in laboratories rather than at actual competitions, so no one is really sure if it works in the field the same way it does in the laboratory.
According to the researchers, many factors can affect exercise performance and the physiological response to caffeine during exercise, including a person’s typical or habitual caffeine intake. Caffeine appears to increase fat oxidation (burning) at rest, but it does not increase fat oxidation after the first few minutes of exercise.
The use of caffeine as a significant fat-burning aid during exercise is not supported by the scientific literature.
Q: Can calcium supplements increase your risk for kidney stones?
A: According to the National Research Council’s Recommended Dietary Allowances (10th edition), it’s better not to exceed the recommended daily allowance (RDA) for calcium. Too much calcium may cause constipation, deteriorated kidney function, and other problems. It can also increase the risk of developing urinary stones in healthy males with already high levels of calcium.
The recommendations, called Daily Reference Intakes (DRIs), for calcium from food and dietary supplements are as follows:
* Women aged 19-50: 1,000 milligrams * Women aged 51-70+: 1,200 milligrams * Pregnant women: 1,000 milligrams * Lactating women: 1,000 milligrams * Men aged 19-50: 1,000 milligrams * Men aged 51-70+: 1,200 milligrams
* Women aged 19-50: 1,000 milligrams * Women aged 51-70+: 1,200 milligrams * Pregnant women: 1,000 milligrams * Lactating women: 1,000 milligrams * Men aged 19-50: 1,000 milligrams * Men aged 51-70+: 1,200 milligrams
Q: What is a calorie?
A: A calorie is a unit of energy. A calorie spelled with a lowercase c is the amount of heat required to raise the temperature of 1 gram of water 1 degree Centigrade. This is the term used by scientists in chemistry and biochemistry, and it is equal to 4.184 joules (J).
A calorie is such a small unit of measurement that food scientists tend to express the energy value of food in terms of a Calorie spelled with a capital C, or more accurately, a kilocalorie (kcal). A kilocalorie is the amount of heat required to raise the temperature of 1,000 grams (or 1 kilogram) of water 1 degree Centigrade. Calorie and kilocalorie are synonymous terms used in human nutrition and metabolic studies.
Q: How many calories does an athlete need each day?
A: Athletes’ calorie needs range widely, depending on the age of the athlete, the time of year, the intensity of training, and the sport. Calorie needs commonly fall within the range of 15 to 25 calories per pound of body weight.
Those on the low end are often smaller individuals who are trying to maintain a low percentage of body fat and who do not participate in endurance exercise events. These might include gymnasts, figure skaters, dancers, and wrestlers.
On the higher end are athletes who are trying to build muscle and/or perform endurance exercise, such as weight lifters, long-distance athletes, and mountain climbers.
Q: What are carbohydrates and why are they important in a healthy diet?
A: Carbohydrates, along with protein and fat, make up the energy-yielding nutrients found in food. The major role of carbohydrates in the body is to provide fuel or energy for all the body processes. In fact, certain tissues in the body, such as the brain and nervous system, derive energy only from glucose, a form of carbohydrate.
A diet that is rich in carbohydrates means that the body does not need to use protein as a fuel source, freeing protein to perform its primary job of making and maintaining muscles and other body tissue. Additionally, using carbohydrate as fuel places less stress on the body and its organs than using protein as fuel.
Good food sources of carbohydrates include fruits, vegetables, grains, breads, cereals, and dairy foods. These carbohydrate sources are also important sources of vitamins, minerals, fibers, and other important phytochemicals.
Q: I have had weight issues for many years. I have found that if I eat carbohydrates I am very tired with no energy at all. If I steer clear of carbohydrates I have more energy and I seem to be able to make it through the day. What is the least amount of carbohydrates I can have and not do any damage to my body?
A: The body actually needs very little carbohydrate to survive. But 'just surviving' is probably not your goal.
Carbohydrate is the body's preferred source of fuel. When added appropriately to the diet, the right amount of carbohydrate should make you feel energetic. You should choose whole grain cereals and breads, raw and cooked vegetables, and fruits as your primary sources of carbohydrate. Combine these foods at meals and snacks with other foods that contain small amounts of protein and/or fat—a turkey sandwich, for example, or cereal with milk—to slow absorption times and maintain more even blood sugar levels.
A generally healthful diet contains approximately 60 to 65 percent carbohydrate, 15 percent protein, and less than 30 percent fat.
My first suggestion is to begin to track what you are actually eating by keeping a log. This will let you know how much carbohydrate, protein, and fat you are actually eating, as well as calories.
There are several possible explanations for your situation. Most likely, the explanation is a combination of several factors.
1. The foods that you describe as carbohydrate foods may also contain large amounts of fat, such as a baked potato with sour cream, a bagel with cream cheese, or a commercial muffin. The high amounts of fat are slowly digested and absorbed, and they may make you feel sluggish.
2. When you eat foods that are predominantly high in carbohydrates, and especially refined carbohydrates, you may not be combining them at the same meal with foods high in protein and/or fat. In this case, the carbohydrate is rapidly digested and absorbed, resulting in a surge of the hormone insulin, which rapidly moves the digested carbohydrate (blood sugar) into your cells. This causes a short-lived drop in blood sugar levels that may make you feel fatigued, or low on energy.
3. Less likely explanations include various metabolic disturbances, which should be checked by your physician.
Q: What is creatine, and what effect can it have on athletic performance?
A: Creatine is a substance produced in the liver and kidneys—at a rate of about 2 grams a day—from the nonessential amino acids arginine, glycine, and methionine.
About 95 percent of the body’s creatine travels by the blood to be stored in the muscles, heart, and other body cells. Inside muscle cells, creatine is turned into a compound called creatine phosphate (CP).
CP serves as a tiny energy supply, enough for several seconds of action. CP thus works best over the short haul, in activities like strength training that require short, fast bursts of activity. CP also replenishes your cellular reserves of adenosine triphosphate (ATP), the molecular fuel that provides the power for muscular contractions. With more ATP around, your muscles can do more work.
You can load creatine into your muscle, just like endurance athletes do with carbohydrates. Consequently, you can push harder and longer in your workouts because creatine boosts the pace of energy production in your muscle cells.
Creatine supplementation does not build muscles directly, but it does have an indirect effect. It allows you to work out more intensely, and this translates into muscle gains. More muscle equals more power equals enhanced athletic performance.
Q: Why is a diet high in fat dangerous?
A: First, a high-fat diet is often a high-calorie diet, which will promote obesity and being overweight. Being overweight or obese is a primary risk factor for the development of many diseases, including heart disease, diabetes mellitus, many types of cancers, and degenerative osteoarthritis.
Even if you aren’t obese or overweight, a high-fat diet has a negative influence on the risks of developing many of the same diseases, including heart disease and cancer. People who have high-fat diets often do not consume enough other important foods and nutrients. These include fruits and vegetables, vitamins, minerals, phytochemicals, and fibers, which are important for promoting health and preventing disease.
Q: What are the symptoms of dehydration?
A: I have broken the symptoms of dehydration down into early signs and severe signs.
Early signs: Fatigue Loss of appetite Flushed skin Burning in stomach Light-headedness Headache Dry mouth Dry cough Heat intolerance Dark urine with a strong odor
Severe signs: Difficulty swallowing Stumbling Clumsiness Shriveled skin Sunken eyes and dim vision Painful urination Numb skin Muscle spasm Delirium
Q: Is there a difference between a nutritionist and a dietitian?
A: There is a difference between a registered dietitian (RD) and any other title referring to an individual who works with food and/or nutrition. A registered dietitian has a minimum of a four-year undergraduate college degree in nutrition or a related field that meets the requirements set by the Commission on Dietetic Registration (CDR, a national certifying body). Registered dieticians must also complete a supervised field experience (internship) that meets requirements set by the CDR and pass a national examination certified by the CDR.
Q: You recommend eating a small snack before working out. Other experts say the best time to work out is first thing in the morning and on an empty stomach. What are the benefits of eating before working out?
A: Eating an hour or more prior to exercise has several benefits:
1. It fuels and hydrates the body.
2. It prepares the body with necessary nutrients for recovery and muscle growth after exercise.
3. It may limit the amount of tissue damage that naturally occurs with intense exercise.
If it is difficult for you to eat early in the morning before your workout, make sure that your daily nutrition meets your body's needs. Drink water or a sports drink before your workout to enhance hydration and to provide a small amount of fuel for your body. You could also try a blended beverage, like a homemade smoothie or a liquid meal replacement beverage of around 200 calories of carbohydrate and protein. You’ll feel better during your workout and afterward.
Q: I've recently gained about 5 pounds for seemingly no reason. I work out for an hour and a half most days (5-6/week), I eat a mostly vegetarian diet, and I seldom drink alcohol. I haven't changed any of my habits lately, so I'm wondering if it's possible my weight gain could be because I'm consuming too few calories and my body is in 'starvation mode.' Also, I live in NYC, so I walk everywhere and climb a lot of stairs! I've started cutting back even more food, for fear of gaining more weight, but this hasn't helped. Why have I gained weight when I hardly eat anything??
A: The syndrome of starvation adaptation can occur over a period of time when the number of calories consumed is so low that the body slows down its metabolism to meet the available energy supply. By continuing to lower your calorie intake, you will only make this problem worse.
However, it is impossible to diagnose this problem without a physical examination by a physician and a nutritional history by a registered dietitian working with the physician. There are also other possible medical explanations. I encourage you to seek medical advice from your physician and a registered dietitian. To find a registered dietitian in your area, go to the Eatright Web site for a referral from the American Dietetic Association.
Q: How do egg protein and soy protein compare?
A: The quality of protein is generally classified in one of two ways. The traditional method, called the Protein Efficiency Ratio (PER), determines the weight gain of growing rats fed a particular protein in comparison to a standard protein (egg whites). The higher the PER value, the better the protein.
The more contemporary method compares the amino acid profile of a protein to the essential amino acid requirements in humans established by the United Nations Food and Agriculture Organization. This method, known as the protein digestibility corrected amino acid score (PDCAAS), is recognized internationally as the best method of comparing proteins for humans. A protein with a PDCAAS of 1.0 indicates that the protein exceeds the essential amino acid requirements of the body and is an excellent source of protein.
Protein (PDCAAS/PER) Comments
Ovalbumin (egg); PDCAAS 1.00 / PER 2.8
Protein from egg whites is considered the reference standard to compare protein quality. Egg protein powders were once considered the best source of protein for supplements. However, egg protein is fairly expensive compared to other forms of quality protein. Therefore, use of egg protein in supplements has decreased.
Soy; PDCAAS 1.00 / PER 1.8–2.3
Soy is a high-quality protein extracted from soybeans. Soy protein concentrate (70 percent protein) and isolate (90 percent protein) are particularly good protein sources for vegetarians. Soy protein also contains isoflavone glucosides, which have a number of potential health benefits.
Q: How does regular exercise reduce body fat?
A: Exercise accomplishes two goals. First, it burns calories, which when combined with a calorie-reduced diet will help reduce body fat. Second, exercise builds muscle, the energy-burning tissue in the body. The more muscle you have, the more energy you burn to reduce fat in your body.
Q: Does exercise stimulate appetite?
A: Appetite is a highly individualized characteristic. It waxes and wanes depending on the intensity of exercise, as well as with the perception of the individual. Research studies are not wholly in agreement, but it appears that in general, appetite may be stimulated by exercise that is low to moderate in intensity. High-intensity exercise seems to inhibit appetite immediately after exercise. For people who exercise every other day, appetite seems to be stimulated on the nonexercise day. This may make up for any caloric deficits created on the exercise day.
Q: Do fat-free foods contain any fat?
A: According to labeling regulations, “fat-free” foods can contain no more than 1 gram of fat. So yes, they can contain some fat.
Q: What is the difference between saturated and unsaturated fat?
A: Dietary fats are composed of a string of carbon atoms bonded to hydrogen atoms. A fat in which all bonds between the carbon atoms are single bonds is known as a saturated fat because all the carbon atoms are filled to the brim, or saturated, with hydrogen atoms. Unsaturated fats have one or more double bonds between carbon atoms. They are called unsaturated because their structure still has room to bond with additional hydrogen atoms. Unsaturated fats with just one double bond between carbon atoms are known as monounsaturated fat. Those with two or more double bonds between carbon atoms are known as polyunsaturated fats.
Saturated fats have a hard consistency at room temperature. Foods high in saturated fats include beef, dairy products, commercially prepared baked goods, and tropical oils, such as coconut, palm, and palm kernel oils. These fats can raise blood levels of low-density lipoprotein (LDL) cholesterol to potentially dangerous levels. LDL cholesterol, commonly referred to as bad cholesterol, carries cholesterol in the blood to body cells. High levels of LDL cholesterol can lead to an increased risk of heart disease caused by cholesterol and fat deposits in the arteries.
Unsaturated fats are liquid at room temperature. They contain key nutrients, called essential fatty acids, that cannot be manufactured in the body and so are required in the diet in order to promote normal growth, skin integrity, and healthy blood and nerves. Two of the most important fatty acids are linoleic acid, found mostly in vegetable oils like corn and sunflower, and alpha-linolenic acid, found mostly in soybean and canola oils.
Both monounsaturated fats and polyunsaturated fats have been associated with lower levels of blood cholesterol. Monounsaturated fats have also been shown to lower LDL cholesterol in the blood while maintaining higher levels of high-density lipoproteins (HDL) cholesterol, often referred to as the good cholesterol. HDL cholesterol removes excess cholesterol from the body. People who have high blood levels of HDL cholesterol typically have a lower risk of heart disease. Monounsaturated fats are plentiful in olive oil, canola oil, peanut oil, shellfish, and fish from cold waters, such as salmon, halibut, mackerel, swordfish, black cod, and rainbow trout.
Q. What is an essential fatty acid, and why is it important in a healthy diet?
A. Fatty acid is the chemical term for the individual strands of molecules that make up the larger compound that we think of as fat. There are many fatty acids. Among all the fatty acids used by the body only two cannot be synthesized by the body in adequate amounts, and must therefore come from our diets. These two are linoleic acid and alpha-linolenic acid, and are called essential fatty acids. Essential fatty acids are required by the body for optimal health, normal growth, skin integrity, and healthy blood and nerves. Good sources of essential fatty acids include vegetable oils, nuts, and seeds.
Q: What is fiber, and why is it important in a healthy diet?
A: Fiber is an indigestible carbohydrate found in plant foods. Food nutritionists classify fiber according to its ability to dissolve in water. Water-soluble fibers, found in barley, rice, corn, oats, legumes, apples, pears, citrus fruits, bananas, carrots, dried plums, cranberries, seeds, and seaweed, have been shown to help regulate blood sugar and lower blood cholesterol. Water-insoluble fibers assist with the elimination of bile acids, preventing the formation of gallstones. In addition, cellulose, the roughage found in water-insoluble fibers, acts as a stool softener and bulk former, improving elimination and flushing carcinogens from the system. Good food sources of water-insoluble fibers include root and leafy vegetables, whole grains, legumes, unpeeled apples and pears, and strawberries.
Diets low in fiber have been linked to dozens of medical problems, including heart disease, cancer, diabetes mellitus, diverticulosis, and gallstones. The American Dietetic Association recommends that a healthy diet include 20 to 35 grams of fiber per day.
Q: What are food additives and do they add any nutritional benefits to food?
A: A food additive, broadly defined, is any substance used in or around food that may become a component of the food. Some food additives—called intentional additives—are introduced specifically for the purpose of improving the nutritive value, taste, texture, or shelf life of the product. Other additives enter food as residues after some stage of production or manufacture; these are known as incidental additives.
Q: What is food irradiation?
A: Food irradiation is a preservative process that is being considered more widely in our food supply as an alternative to chemical additives. It treats food with radiation to kill pests and bacteria. In this process, food is conveyed through a lead-lined chamber, where it is exposed to cobalt-60, a radioisotope that has been used in hospital settings for more than 30 years. The Food and Drug Administration (FDA) regulates the doses, which are carefully measured and monitored. The food has no chance to become contaminated with radioactivity.
Even so, this process raises some legitimate concerns. Studies have shown that food irradiation alters nutrients and chemicals in foods in much the same way canning, freezing, pasteurization, and cooking do. Not only that, irradiation forms new substances in foods—substances not present prior to processing. As yet, we have limited information on the health effects of consuming these by-products of irradiation. Tests on the process are ongoing.
However, the FDA has already given a go-ahead to the use of irradiation within specified doses for spices, some meats, fruits, and vegetables. The process is supposed to thwart insect infestation, kill Trichinella spiralis (the pork parasite responsible for widespread disease), and keep tuberous vegetables (such as potatoes) from sprouting.
Q: What are the health benefits of green tea?
A: The media and marketing claims for green tea are that it is a strong antioxidant and anticancer agent, that it protects the heart, and that it fights viruses and bacteria.
Although much more research is needed before we can draw conclusions, evidence from laboratory, animal, and population studies suggests that green tea does in fact have anticarcinogenic effects, meaning that it might protect against cancer. Also, chemicals found in green tea called polyphones have demonstrated antioxidant capabilities both in the laboratory and in humans.
At this time research does not support claims that green tea protects the heart from high cholesterol levels or promotes resistance to the oxidation that causes arterial plaques. Preliminary evidence shows that green tea extract might inhibit bacterial growth and the influenza virus, but more research is needed to confirm these studies.
Q: What is the difference between HDL and LDL cholesterol?
A: HDL means “high-density lipoprotein,” and LDL means “low-density lipoprotein.” There are many fractions of total cholesterol in our bloodstream. HDL and LDL are two of the fractions that carry cholesterol.
Research shows that LDL and HDL are highly associated with risk of developing heart disease. LDL, also called “the bad cholesterol,” allows cholesterol to build up in arteries and can ultimately clog arteries enough to cause a heart attack or a stroke. HDL, also called “the good cholesterol,” helps clear cholesterol out of the bloodstream and ultimately out of the body.
The higher your levels of LDL, the greater your risk for heart disease. The lower your LDL levels, the lower your risk for heart disease. The opposite is true for HDL. The higher your HDL levels, the lower your risk for heart disease. Low HDL levels are associated with a greater risk for developing heart disease.
The American Heart Association Web site offers the following information:
Cholesterol is measured in milligrams per deciliter of blood (mg/dL). Healthy LDL and HDL cholesterol levels:
LDL: less than 160 mg/dL (less than 130 mg/dL if you have two or more other risk factors for heart disease)
HDL: greater than 40 mg/dL
Total cholesterol
Less than 200 mg/dL = desirable blood cholesterol
200 to 239 mg/dL = borderline-high blood cholesterol
240 mg/dL and over = high blood cholesterol
Q: Will drinking a beverage high in sugar content within an hour of exercise help or hinder athletic performance?
A: I don’t recommend that you consume sweet foods and beverages within an hour of exercise primarily because they will not be emptied quickly from the stomach, and they may even have a dehydrating effect on cells by drawing fluids out of the cells to create an osmotic balance or equilibrium.
In some individuals, insulin levels may peak to cover the high intake of carbohydrate, causing a drop in blood sugar levels early into exercise that may diminish performance. However, consuming a carbohydrate snack or a beverage containing 6 to 8 percent carbohydrate, such as a sports drink, within an hour of exercise may enhance both hydration and energy availability, thereby helping performance.
Q: What happens in the body when an athlete “bonks” or ”hits the wall”?
A: An athlete “hits the wall” when stores of muscle glycogen (the stored carbohydrate in muscle) get too low. An athlete who “hits the wall” during a race will feel tremendous fatigue and want to quit.
Different from “hitting the wall,” “bonking” is when liver glycogen stores are depleted, with or without a depletion of muscle glycogen. During exercise, stored glycogen in the liver maintains normal blood sugar levels so that the brain can function. When liver glycogen levels are depleted and blood sugar levels drop, athletes feel weak, uncoordinated, light-headed, and unable to concentrate.
Q: You recommend eating a full meal two hours after working out. But it’s 9 p.m. by the time I’m done working out, and I'm trying to lose a few pounds. What should I eat so late at night?
A: It is hard to eat so late at night, but your body needs nourishment after exercise to recover, build, and refuel for your next workout. Fluids and carbohydrates are the most important. And if you still need protein to balance out your day's needs, you should have it before you go to bed too. The meal can be small, about 250 to 300 calories. Make sure to drink water. You could also eat a bowl of cereal with milk, a turkey sandwich, or a tuna salad with a baked potato. If you prefer to drink rather than eat, try a meal replacement beverage that contains about 300 calories of carbohydrate and protein.
Q: What are very low calorie diets and who benefits from them?
A: Very low calorie diets (VLCDs) usually provide fewer than 1,200 calories per day. Anyone following this type of program should be under medical supervision. These types of diets have been shown to be useful for obese individuals who are beginning a weight-loss program. However, in order to maintain any weight loss, individuals must move toward and be instructed in planning and preparing a well-balanced diet of food. They must also be educated in lifestyle modification techniques, including exercise and stress reduction.
Q: What is the best meal to eat before a marathon?
A: In her book Eating for Endurance, Ellen Coleman recommends the following:
“Consume 1-4 grams of carbohydrate per kilogram of body weight, 1-4 hours before exercise. To avoid potential gastrointestinal distress, reduce the size of the meal—making it smaller as it is consumed closer to exercise time. For example, a carbohydrate feeding of 1 gram per kg of body weight (4 calories per kg) is appropriate an hour before exercise, whereas 4 grams per kg (16 calories per kg) can be consumed 4 hours before exercise.”
Consumption of fatty foods should be limited in the pre-event meal since they are digested more slowly and may make you feel sluggish. Watch out for high-protein foods that are also high in fat, like egg yolks, fried eggs, and cheese. Limit the amount of fiber in your pre-event meal, too. It will slow down digestion and make you feel full.
Good pre-event choices include fruit, bread products, jams and jellies, nonfat or low-fat yogurt, fruit juices, and nonfat milk. Liquid meals or high-carbohydrate supplements may also be useful. They are rapidly emptied from the stomach, making the nutrients readily available without leaving you feeling too full.
Make sure you are well hydrated, and don’t depend on drinking a couple of glasses of water before your event. It takes at least 24 hours for the body to become fully hydrated once it has been dehydrated. So have a fluid plan before your race, just like you have a food plan.
Lastly, try out your pre-event fluid and food plan during a training run before race day to make sure it works for you. Never try something on the day of the race that you have not tried before.
Q: Do multivitamins contain other ingredients besides vitamins and minerals?
A: A multivitamin may contain only vitamins, or it may contain vitamins and minerals. Other nonessential nutrients may also be added. Since there is little regulation of the nutritional supplements industry, it is wise for all consumers to read labels and be well informed prior to purchasing nutritional supplements.
Fillers, such as cellulose, are often used to bulk the vitamin pill and hold it together. Drying agents, such as silicon, may be used to keep the pills from becoming soggy from water in the air.
There are a number of agents that are used to coat the pills as well. All of these should be listed clearly on the label. If you have any questions about these ingredients, you should contact the manufacturer and/or the U.S. Food and Drug Administration.
Q: I have a friend who runs long distances—marathons and such. He says he can't bend over and touch his toes because his muscles are so tight. I am a molecular biologist, and I seem to recall that lactose dehydrogenase may play a role in my friend’s condition. Is there a dietary connection? If not, what could be causing this? Is there any way to reduce his muscle tightness?
A: Flexibility is influenced by a number of things, most notably genetics and training. To maintain and increase flexibility, one must practice flexibility routines, just as one must exercise to enhance exercise performance. It is unlikely that lactase buildup in the muscles would be responsible for chronic muscle tightness, since lactase buildup is a transient condition that follows exercise. I suggest that your friend consult with a certified personal trainer and/or a sports medicine physician to resolve the issue.
Q: What does the term “organic” on a food label mean?
A: Foods that are certified organic are grown in soil enriched with organic fertilizers, rather than synthetic fertilizers, and are treated only with nonsynthetic pesticides. More specifically, it means that the food has been produced, stored, processed, and packaged without the use of synthetic fertilizers, herbicides, fungicides, or pesticides for one year prior to the appearance of flower buds in the case of perennial crops and one year prior to seed planting in the case of annual crops.
Organic farms use a soil-building program that promotes vibrant soil and healthy plants, usually including crop rotations and biological pest control.
Q: Will a diet high in milk and other dairy products prevent osteoporosis?
A: A diet high in milk and other dairy products that provide the nutrients essential for building and maintaining bones is one important factor in decreasing the risk of developing osteoporosis. There are other ways that a person can decrease the risk of developing osteoporosis. These include getting at least 30 minutes of moderate exercise each day, not smoking, and limiting alcohol and caffeine intake.
Other factors are difficult or impossible to control. People with a family history of osteoporosis are more likely to develop the disease, as are women who have gone through menopause and people who take certain medications. Women who have gone through menopause, women who experience an abnormal absence of menstrual periods (amenorrhea), and individuals who have a low bone density in early adulthood are also at higher risk.
Q. What is protein, and why is it important in a healthy diet?
A. Protein is a macronutrient with a chemical structure containing carbon, hydrogen, oxygen, and nitrogen. It is the nitrogen that gives protein its unique properties. Protein is made up of smaller units called amino acids, which are connected together like a strand of pearls. If two strands of pearls were wound together and then twisted to double up on each other, they would resemble a protein molecule.
Your body breaks down protein from food into amino acids and reshuffles them into new protein to build and rebuild tissue, including muscle. Protein also keeps your immune system functioning up to par, helps carry nutrients throughout the body, has a hand in forming hormones, and is involved in important enzyme reactions such as digestion.
There are 20 different types of amino acids, and all can be combined to form the proteins necessary to build the body and keep it healthy. Some of these amino acids can be made by the body and are called nonessential amino acids.
Others have to be supplied by the foods you eat. These amino acids are termed essential amino acids.
Animal and plant foods contain all 20 amino acids (but in different amounts depending on the food). Animal proteins and soy protein are of higher quality because they contain all the essential amino acids in larger amounts and better proportions. In plants, amino acids exist in smaller concentrations. For the body to make proteins properly, all 20 amino acids must be present at the same time.
Although amino acids work together to form body proteins, individual amino acids have specific roles to play in the body. Certain amino acids, such as tryptophan and tyrosine, are involved in the formation of chemical messengers called neurotransmitters for the brain and nervous system. Three amino acids (leucine, isoleucine, and valine) are constituents of muscle tissue.
Q: How do Recommended Dietary Allowances(RDA), the U.S. Recommended Daily Allowances (U.S. RDA), Reference Daily Intakes (RDI), and Daily Reference Values (DRVs) differ from one another?
A: The Recommended Dietary Allowances (RDA) were developed by the Food and Nutrition Board of the National Academy of Sciences in 1943. It provides a guide for the amounts of specific nutrients healthy people of the same gender and of similar ages need to consume to prevent deficiency problems. The recommendations have been revised every four to six years in response to new scientific information. These guidelines serve as the scientific basis for programs such as the United States Department of Agriculture’s Dietary Guidelines and National School Lunch Program.
The United States Recommended Daily Allowances (U.S. RDA) is the old name used for standards established by the Food and Drug Administration (FDA) that were used on food nutrition labels. The U.S. RDAs are a compilation of the guidelines found in the RDAs using the highest RDA values within specific age and gender categories, including children over 4 years and adults, infants less than 1 year, toddlers 1 to 4 years, and pregnant and lactating women.
Partly because the U.S. RDA was often confused with RDAs, in 1993 the FDA changed the name of U.S. RDAs to Reference Daily Intakes (RDI). In addition, the FDA established the Daily Reference Values (DRV) for nutrients such as fat and cholesterol for which no set of standards previously existed. Today the RDI and the DRV are used to form a single list of nutrient values known as Daily Values (DV) that are now used on nutrition labels.
Q: What factors determine if a weight loss program is sound and not a fad?
A: A healthy weight loss program should include a daily intake of at least 1,200 calories and should include all the food groups: fruits and vegetables, grains, dairy, protein foods, and fats. It should promote lifestyle modification such as exercise and offer techniques for learning how to change habits.
The basis of the diet should be food. A sound program helps people move from using a tool to help control calories and food choices toward a diet based solely on whole foods. The goal should be achieving and maintaining a healthy weight.
Ultimately, the dieter should be able to maintain weight loss without using any weight-loss tools. A fad diet will often make unsubstantiated claims, be very low in calories, eliminate whole food groups, use scare tactics and fear to attract the consumer, require that the dieter purchase foods only available from the program purveyor, and avoid teaching the dieter how to manage weight without the diet product.
Q: I have a B.S. in biochemistry and a master’s in education. I am currently teaching, but I’m extremely interested in your field. What are the options for a career in sports nutrition?
A: The field of sports nutrition is just taking off. Options include academic research and teaching, positions in industry (working for food or supplement manufacturers), consulting, and private practice. Individuals build a consulting business through experience in several ways, including spending time at a fitness facility, doing individual counseling, consulting with business and industry, writing and media work, and working with sports teams. This is a highly specialized field, and it requires academic degrees in nutrition and exercise science. Personal experience as an avid exerciser or athlete is also beneficial.
Q: Can tofu increase a person's risk for dementia?
A: There is one study published by researcher Lon White in the Journal of the American College of Nutrition that documented an association between the consumption of two or three servings of tofu per week in midlife (as a lifelong habit) and the early development of senile dementia and Alzheimer-related diseases in Japanese American men living in Hawaii. These dementias occurred about five years earlier than would have been predicted. A much less significant effect was observed in the women in the study.
The quantity consumed by the subjects of the study is much greater than the average American intake of tofu and soy. And this is just one study; it is not definitive proof of anything. Other documentation shows that the benefits of soy foods are hundredfold. I advise clients that, just like anything else, moderation is the key. When eaten in extremes, anything can become harmful.
Q: What are trace minerals and why are they important in the diet?
A: The body requires minerals in minute amounts. Like vitamins, they don’t yield any energy, although some play a behind-the-scenes role in energy production. Trace minerals are found in the body in the smallest concentrations and are needed in smaller amounts than the major minerals. The trace minerals are iron, iodine, chromium, fluoride, and molybdenum. In the following list, the trace minerals are given along with their function and the best food sources for obtaining them.
Iron
Function: Oxygen transport to cells; formation of oxygen-carrying red blood cells; required for the production of certain antioxidant enzymes
Sources: Liver, oysters, lean meats, green leafy vegetables
Iodine
Function: Energy production; growth and development; metabolism
Sources: Iodized salt, seafood, sea vegetables, mushrooms
Chromium
Function: Normal blood sugar; fat metabolism
Sources: Corn oil, brewer’s yeast, whole grains, meats
Fluoride
Function: Bone and tooth strengthening
Sources: Fluoridated water
Molybdenum:
Function: Fat metabolism
Sources: Milk, beans, breads, cereals
Q: What are triglycerides?
A: Triglycerides are the chemical form in which most fat exists in food as well as in the body. They're also present in blood plasma and in association with blood cholesterol. Triglycerides in plasma are derived from fats eaten in foods or made in the body from other energy sources, such as carbohydrates. Calories ingested in a meal and not used immediately by tissues are converted to triglycerides and transported to fat cells to be stored.
Hormones regulate the release of triglycerides from fat tissue to meet the body's needs for energy between meals. Excess triglycerides in plasma is called hypertriglyceridemia. It's linked to the occurrence of coronary artery disease in some people. Elevated triglycerides may be a consequence of other diseases, such as untreated diabetes mellitus. Increases in triglyceride levels can be detected by plasma measurements.
According to the American Heart Association Web site, the Second Expert Panel on the Detection, Evaluation and Treatment of High Blood Cholesterol in Adults defined levels for hypertriglycerides. Here are their definitions:
Normal triglycerides - less than 200 mg/dL Borderline-high triglycerides - 200 to 400 mg/dL High triglycerides - 400to 1,000 mg/dL Very high triglycerides - greater than 1,000 mg/dL These are based on fasting plasma triglyceride levels. *From the American Heart Association Web site.
Normal triglycerides - less than 200 mg/dL Borderline-high triglycerides - 200 to 400 mg/dL High triglycerides - 400to 1,000 mg/dL Very high triglycerides - greater than 1,000 mg/dL These are based on fasting plasma triglyceride levels. *From the American Heart Association Web site.
Q: Which is better to drink during exercise—water or a sports beverage?
A: This depends on the exercise intensity and duration. When exercise is moderate in intensity and lasts one hour or less, water is the best sports drink around.
Sports beverages will enhance your performance if you are exercising at high intensity for 45 minutes or more, doing intermittent bouts of high-intensity exercise (such as soccer) for 45 minutes or more, or exercising at moderate intensity for 60 to 90 minutes or more.
Research shows the best beverages to drink during physical activity are 6 to 8 percent carbohydrate solutions (6 to 8 g of carbohydrate per 100 ml of beverage).
Fitness Goals
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Yoga Stretch
The practice of yoga teaches various poses that gently stretch the muscles. Accompanied by certain breathing techniques, these poses are designed to increase strength, flexibility, and circulation. Yoga has been found to be an effective stress-reducer.
If overall fitness or prevention of heart disease is a primary goal, 20 to 30 minutes of moderate-intensity, daily aerobic exercise—such as walking, jogging, swimming, or dance aerobics—should be considered. In general, begin with shorter exercise sessions and gradually work up to 20 to 30 minutes. In addition to reducing risk of heart disease, such an aerobic-exercise program will also help in weight reduction and altering body composition, and in enhancing flexibility.
If improving muscle strength is the primary consideration, regular, high-intensity workouts with weights are more appropriate. Studies have shown that even older people can benefit greatly from a weight-lifting workout. In particular, bone density, often a concern in the elderly, is increased, muscle atrophy (decrease) is prevented, and general strength and coordination are improved by this type of exercise. A structured, supervised weight program after consultation with a physician is recommended.
Stretching exercises, including yoga, will enhance flexibility. In planning an exercise program, be sure to include stretching exercises and warm-up and cooldown periods to prevent muscle pulls and other injuries.
Exercise Intensity
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If an aerobic program is adopted, in addition to duration (at least 20 to 30 minutes) and frequency (daily or several times a week), intensity of the exercise should also be considered. The intensity of the aerobic exercise can be determined by evaluating the heart rate attained during exercise. The maximum heart rate (beats per minute) for an individual is approximately 220 minus age. To improve aerobic capacity (VO2 maximum), exercise should be performed at an intensity that produces a heart rate of at least 70 percent of this maximum. For a 20-year-old, for example, the maximum heart rate is 220 - 20, or 200. The heart rate should rise to at least 140 (70 percent of 200). You can determine your heart rate by placing two fingers over the radial artery in the wrist or the carotid artery of the neck. By keeping an occasional record of heart rate responses to a standard exercise (for example, jogging at a rate of 1 mile per ten minutes), it is possible to track your fitness progress; over a period of several weeks, the same exercise will produce a lower heart rate. Similarly, the intensity of exercise (such as the speed of jogging) required to produce a given rise in heart rate will increase.
The most important aspect of getting in shape is to make exercise an integral part of one's lifestyle. Exercising to stay as physically fit and healthy as possible should be a lifelong commitment, and is especially important to people who perform little physical work in their day-to-day lives.
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