Nutrition and Exercise Science

Introduction Optimal genetic endowment, optimal training and a suitable socioeconomic environment are three keys to success in physical activity When athletes attain an elite level within their sport, they tend to be very homogeneous in terms of genetics, training and environment It is becoming increasingly clear that nutritional practice can either hamper or improve an athlete’s performance

The energy value of food Calories equals the amount of heat required to raise the temperature of 1g water from 14.5 to 15.5 ℃ CHO and protein release about 4 kcal/g Fats release more than 9 kcal/g Nutrition Facts

Nutritional label allows us to determine the relative proportions of fat, protein, and carbohydrate in each serving

Components of the Athletes’ Diet Daily food intake should include about –CHO : 55%-70% –Protein : 12%-15% –Fat : 20%-30%

Carbohydrate (CHO) CHO is the primary fuel for certain forms of exercise Is the most readily available fuels Dietary CHO comes in two forms –Starch –Sugar Glucose is stored in the body as the complex CHO called glycogen Liver glycogen maintains blood glucose level Muscle glycogen does not provide glucose to bloodstream and serves as one of the preferred fuel sources for energy by the muscle

Glycogen

Blood Glucose Control

Influence of Exercise Intensity on Muscle Fuel Source

Effect of Exercise Duration on Muscle Fuel Source

How much Carbohydrate is Enough Eat 55% to 70% total calories from CHO, that is about 5-10g CHO/kg body weight per day Relative levels of protein, CHO, fat required depends on the duration and intensity of exercise

How much Carbohydrate is Enough Consumption of a large quantity of CHO between exercise sessions can help maintain muscle glycogen levels This delays fatigue that may occur when blood glucose levels drop too low

Fats Dietary fat is essential in our diet A healthy diet contain 20 to 25% fat calories Athletes who need more than 3500 calories per day to maintain their weight and training must be more liberal with fat intake

Fats Fuel source selection is dependent on the level of aerobic power required At higher aerobic power requirements, the sympathetic nervous system (SNS) may provide important hormonal stimulation for metabolism → Training → ← SNS Stimulation ←

Proteins Protein is about 12 to 15% of our daily energy intake Most of us only use 2 to 5% of this protein to provide energy for activity Remaining protein is used to repair and restore tissue on a daily basis, or provide a substrate for growth and development

Proteins In endurance activities up to 15% of the energy expended during exercise can come from protein RDA for adults is 0.8g of protein/kg desirable weight Athlete in the initial stages of resistance-type training involving a significant rate of muscle building should consume about 1.5g/kg desirable weight

Fluids and Hydration Water makes up 50 to 60% of the body weight Water also comprise 83% of blood, 70% of muscle, 30% fat, and 10% of bone

Sources of fluid intake and loss Water intake –Drink 1000 ml –Water content in food 1000 ml –Water produced from metabolism 350 ml –Total intake 2350 ml Water output –Skin perspiration 500 ml –Lung respiration 400 ml –Urine 1300ml –Colon loss 150 ml –Total output 2350 ml

During exercise, the rate of heat production by active muscles can be as much as 100 times that of inactive muscles One g of evaporated water form the skin removes about 0.6 calories of heat from the body Fluid replacement is imperative during exercise to prevent dehydration and its possible catastrophic consequences A loss of body weight due dehydration –1% → thirst –3% → impaired exercise tolerance –5% →impaired heat tolerance Only 50 to 60% of the fluids lost during exercise can be replenished during exercise

Tips for fluid replenishment Intense workout lasting longer than 1 hour in high heat and humidity, sport drink may be advantage Drink 2 to 4 cups fluids per 1 hour of exercise Keep the fluids cool if possible Drink 4 to 8 ounces each time, This voulme is optimal to stimulate the stomach to contract and empty fluids into the small intestine Drink every 15 min of exercise

Vitamins and Minerals Athletes tend to consume many more vitamins (e.g. Vita. B) and minerals along with the calories Minerals tend to be suboptimal in many athletes’ diets, especially the diets of women athletes who have greater iron losses than nonathletes, and this is associated with intense training Menopause need 15 to 10 mg iron per day

Performance Eating Optimal performance requires optimal nutrition The principles are the same whether the athletes is involved in active heavy training or in competition

Food Selection Before Performance Eat a diet that is 5 to 10 g of CHO/kg body weight will maintain liver and muscle glycogen stores Events or intense exercise that last more than 2 hours need maximum glycogen stores for optimal performance Never eat foods before an event that have not been tried during training !!

CHO Loading

Food Selection During Performance During an intense workout or event is to rehydrate as quickly as possible Cool water is generally the best choice for fluid replacement Sport drinks may be beneficial if events are longer than 1 hour in duration CHO in beverages not only enhances fluid absorption, but also provide CHO to prevent drops in blood glucose Consuming 0.2 to 0.6 g of CHO/kg body weight per hour of exercise Ultra-endurance athletes must also consider sodium replacements in events lasting more than 8 hours

Food Selection After Performance To recovery quickly from an intense workout or competition of more than 1 hour should focus on both fluid and CHO ingestion More effective time to replenish glycogen occurs within the first 45 minutes after a strenuous exercise bout

Energy Balance If body weight is to be maintained, the amount of energy we expand a daily basis must be matched by the amount of energy we consume

Body Composition Two compartment model in exercise scientist –Fat compartment –Fat-free, or lean body mass compartment Adult woman have about 25% of their weight as fat, while men have about 15% if their weight as fat

Measuring Body Composition Densitometry, Hydrostatic weighting

Anthropometric Measurement of Body Composition

Bioelectrial Impedance Analysis Fat free mass is a good conductor of electrical current and fat is an excellent insulator Measurement of the body’s conductive properties can be used to estimate body composition

Magnetic Resonance Imaging

Summary Points Nutrition is one variable that contributes to athletic performance that can easily be changed using the guidelines provided People who engage in routine intensive physical training need to be concerned about caloric intake, food composition, water balance, and vitamin and mineral intake

To maintain body weight, energy intake must meet energy expenditure, it this does not occur, changes in weight (and ultimately performance) will become evident Carbohydrate intake prior to, during, and after a workout bout or competitive event is also import. CHO can clearly be considered true ergogenic aids

Small deficits in body water can result in dramatic reductions in physical performance. This decline in performance is due to compromised cardiovascular and thermoregulatory capacity. Water intake is critical and must be a conscious priority particularly during exercise in the heat Because of the involvement of vitamins and minerals as cofactors and components essential to metabolic pathways, athletes, trainers, and coaches need to be aware of the dietary patterns of their athletes

Many athletes make poor food selection choices as a result of lifestyle or ignorance such that their diet may be deficient in one or more of these compounds Although coaches cannot alter fiber type, heart size, or limb length, they can influence performance by educating their athletes about proper nutrition In addition to performance benefits, nutrition can also significantly affect health and wellness such that short-term and long-term benefits may be realized

Discussion Can you select two different sports fitting nutritional needs to them in order to promote athletic performances What do you think about the issue of dietary supplementation to the young athletes undertaking a hard physical conditioning. What is your opinion of preventing aging by consuming large quantity of assorted vitamins (e.g. Centrum) daily after fifty.