Sports Fitness Training

The hypothalamus is the neural center for the regulation of food intake. One area of the hypothalamus consisting of the lateral nuclei, controls hunger, or the craving for food. Another area consisting of the ventromedial nuclei, controls satiety, or the feeling of fulfillment. Therefore, drugs or supplements that act on the hypothalamus can act as an anorectic (appetite reducing) agent. Prescription drugs like amphetamine and fenfluramine function by increasing the level of brain catecholamines and 5-hydroxytrypt­amine (serotonin), which causes a feeling of fullness and suppresses the appetite, respectively Some dietary supplements could alter the levels of neurotransmitters in the hypothalamic region and regulate food intake.

The body may also produce its own satiety chemical or hormone that suppresses the appetite. The Set-Point Theory suggests that fat cells prefer to maintain a certain size. When there is a reduction in the size of the adipocyte due to dieting, a signal is sent to the hypothalamus resulting in an increase in appetite. As the fat cell regains its size, another signal is sent to the hypothalamus, which instructs the hypothalamus to reduce or stop the desire to eat.

The maintenance of a perfect body weight is a survival mechanism for higher organisms including mammals. Furthermore, the maintenance of body weight requires both the maintenance of energy and nutrient balance. This means that the diet must contain both adequate amounts of calories, macronutrients (carbohydrate, protein, and fat), and micro nutrients (vitamins and minerals).

Research using rodents may have discovered the signal for the Set-Point Theory. The signal is called leptin, and it appears to have a dual role, it decreases food intake and increases energy expenditure resulting in an increase in fat oxidation. When rats are bred to be deficient in this hormone, it causes them to overeat and become obese. When this hormone is administered to rats, it causes them to stop eating and increases fat oxidation, resulting in fat loss but not a loss in lean tissue (i.e., muscle). However, human research indicates that the hormone is not the problem, but rather the transporter. Obese individuals appear to develop a resistance to leptin that is similar to insulin resistance. Therefore, it may be impractical to expect leptin administration to humans to be a viable means of controlling obesity. If the transporters are already saturated or downregulated from excessive endogenous leptin, it does not make sense to provide more. Therefore, research has begun to focus on the leptin transporter and binding site in hopes of discovering the post-binding signaling cascade and any potential defects in this system. Leptin research is interesting and may one day provide a drug to control obesity, but this probably won’t happen for many years. For more information on leptin, read the excellent reviews by Hwang et al. and by requier and Tappy. Although several mechanisms could be used as a target for fat loss, most of the dietary supplements targeted as a fat loss agent do not have scientific research to support their claims.

The number of walkers, joggers, bicyclists, step aerobics participants, and swimmers is tangible evidence of American’s increased awareness of the most important aspect of physical fitness: cardiorespiratory fitness, which refers to the ability of the circulatory and respiratory systems to supply oxygen during sustained physical activity.

The primary category of physical activity known to improve cardiorespiratory endurance is aerobic exercise. The term aerobic means “with oxygen” and describes any type of exercise, typically performed at moderate levels of intensity for extended periods of time, that increases your heart rate. Aerobic capacity(commonly written as VO₂ max) is defined as the maximum volume of oxygen consumed by the muscles during exercise.

To measure your maximal aerobic capacity, an exercise physiologist or physician will typically have you exercise on a treadmill. He or she will initially ask you to walk or run at an easy pace, and then, at set time intervals during this graded exercise test, will gradually increase the workload(i.e., a combination of running speed and the angle of incline of the treadmill) to the point of maximal exertion. Generally, the higher your cardiorespiratory endurance level, the more oxygen you can transport to exercising muscles and the longer you can maintain a high intensity of exercise prior to exhaustion.

According to the exercise testing guidelines of the American College of Sports Medicine, maximal aerobic capacity treadmill tests should not be conducted on men over 40 or women over 50 without a prior comprehensive physical examination and permission from their physicians.

Aerobic Fitness Programs

Researchers tell us that a physically active lifestyle is the key to improved cardiovascular health, but what level of activity is required to improve aerobic fitness? There are numerous variables in any particular aerobic activity, but for healthy young adults, aerobic activity that works your heart at a moderate intensity(approximately 70 percent of your maximum heart rate, or about 140 to 160 beats per minute) for prolonged periods of time(20 to 60 minutes of continuous activity) will improve your fitness level.

The most beneficial aerobic exercises are total body activities involving all the large muscle groups of your body, for example, swimming, cross-country skiing, or rowing. If you have been sedentary for quite a while, simply initiating a physical activity program may be the hardest task you’ll face. Don’t be put off by the next-day soreness you are likely to feel in your long-dormant muscles. The key is to begin your exercise program at a very low intensity, progress slowly … and stay with it. For example, if you choose an aerobic fitness program that involves jogging, you’ll need several weeks of workouts combining walking and jogging before you will reach a fitness level that enables you to jog continuously for 15 to 20 minutes.

You will need to adjust the frequency, intensity, and duration of your aerobic activity program to accommodate your initial level of cardiorespiratory fitness. As you progress, add to your exercise load by increasing exercise duration or intensity, but do not increase both at the same time.

• Determining Exercise Frequency If you are a newcomer to regular physical activity, the frequency of your aerobic exercise bouts should be at least three times per week. The surgeon general’s recommendation is for moderate amounts of daily physical activity. As your fitness level improves, your goal should be to exercise 20 to 30 minutes per day, five days a week.

• Determining Exercise Intensity Your aerobic exercise program should employ activities of moderate intensity that use large muscle groups and can be maintained for prolonged periods of time. The measure of such a workout is your target heart rate, which is a percentage of your maximum heart rate. To calculate target heart rate, subtract your age from 220 for females or from 226 for males. The result is your maximum heart rate. You determine your target heart rate by calculating a desired percentage of maximum heart rate, often 60 percent. If you are a 20-year-old woman, your maximum heart rate is 200(220 – 20). Your 60-percent target heart rate would be 120(200 x .60). People in poor physical condition should set a target heart rate between 40 and 50 percent of maximum. As your condition improves, you can gradually increase your target heart rate. Increases should be made in small increments: Increase from 40 to 45 percent; then from 45 to 50 percent. Because of the potential risks and adherence-to-exercise problems associated with high-intensity activity(> 80% of maximum heart rate), moderate-intensity activity of longer duration is suggested for adults who are not training for competitive athletics.

Once you know your target heart rate, you can determine how close you are to this value during your workout. You’ll need to stop exercising briefly in order to measure your heart rate. To take your pulse, lightly place your index and middle fingers(don’t use your thumb) over one of the carotid arteries in your neck (along either side of your Adam’s apple), or over one of the radial arteries (thumb side) of your wrist.

Be sure to start counting your pulse immediately after you stop exercising, as your heart rate will decrease quickly. Using a watch or clock, take your pulse for six seconds and multiply this number by 10(just add a zero to your count) to get the number of beats per minute(bpm). Your pulse should be within a range of about 5 bpm above or below your target heart rate. If necessary, increase or decrease the pace or intensity of your workout to achieve your target heart rate.

A target heart rate of 70 percent of maximum is sometimes called the “conversational level of exercise” because you are able to talk with a partner while exercising. If you are a novice and you are breathing so hard that talking is difficult. your intensity of exercise is too high. If you can sustain a conversational level of aerobic exercise for 20 to 30 minutes, you will improve your cardiorespiratory fitness.

The lower the intensity of the activity, the longer the duration you’ll need to get the same caloric expenditure. For example, a 180-pound man will expend 288 calories per hour of playing golf if he carries his clubs, but will burn 805 calories per hour if he is cross-country skiing. Your goal should be to expend 300 to 500 calories per exercise session, with an eventual weekly goal of 1,500 to 2,000 calories.

Since many of the health benefits associated with cardiorespiratory fitness activities take about one year of regular exercise to achieve, you shouldn’t expect an immediate reduction in your risk of cardiovascular disease when you start an exercise program. However, any low-to-moderate-intensity physical activity, even if it does not meet all the cardiorespiratory exercise.

Cardiorespiratory fitness The ability of the heart, lungs, and blood vessels to supply oxygen to skeletal muscles during sustained physical activity.

Aerobic exercise Any type of exercise, typically performed at moderate levels of intensity for extended periods of time (typically 20 to 30 minutes or longer), that increases heart rate.

Aerobic capacity The current functional status of a person’s cardiovascular system; measured as VO₂ max.

Graded exercise test A test of aerobic capacity administered by a physician, exercise physiologist, or other trained person; two common forms are the treadmill running test and the stationary bike test.

Several agents have been promoted to increase fat loss. However, as you have read, minimal scientific data are actually available to support many of these products. The products, which have been shown to be beneficial in aiding fat loss, from a scientific point of view, include caffeine with or without ephedrine. Although caffeine alone or in combination with ephedrine appears to be the most effective, there is some controversy surrounding the use of these ingredients. When abused, ephedrine has been associated with adverse reactions including death. The use of caffeine also produces some unwanted side effects. However, if a caffeine and/or ephedrine product is used according to the manufacturer’s recommendations and if used alone, it is unlikely that any life-threatening events would occur with the use of the product. Nevertheless, appropriate supervision by a physician is always recommended.

An exercise intervention program was used in conjunction with the dietary supplement. The supplement, in most cases, did not produce a great effect, if any. The key to fat loss is that caloric expenditure must be greater than caloric intake. If it is not, fat loss will not occur.

Although new fat reduction supplements will appear on the market, the main physiological mechanism of body weight regulation, energy balance, is reflected by energy intake and energy expenditure. Excess energy intake without a concomitant rise in energy expenditure will result mainly in the deposition of fat into adipocytes. This excess energy may be in the form of carbohydrates, fat, and protein. A balanced diet with energy expenditure exceeding energy intake is the best form of fat reduction-guaranteed.

Reducing Lipid Absorption

Dietary lipid (predominately fat) is digested by specific enzymes including lipases, phospholipids, and cholesterol esterase. Most of the lipid digestion occurs in the duodenum of the small intestine in which lipids are emulsified by the detergent action of bile salts. Lipids and bile salts spontaneously form micelles. The micelles contain fatty acids and cholesterol, and serve as transporters. Micelles migrate to the brush border where lipids diffuse out of the micelles into mucosal cells.

Agents that can prevent lipid digestion and/or absorption appear an attractive approach as a fat loss mechanism or, more importantly, reducing blood cholesterol levels. In fact, there are some prescriptions and fat substitutes that function to reduce fat absorption. However, a reduction in lipid absorption has potentially negative side effects, including gastrointestinal discomfort, diarrhea, and a reduction in the absorption of fat soluble vitamins.