Sports Nutrition Flashcards
carbohydrates
Carbohydrates are categorized as either simple or complex, based on their structure.
To understand the composition of carbohydrates in foods, imagine them as links of chains of varying length.
- The basic unit of a carbohydrate is the monosaccharide molecule. Examples of monosaccharides are
glucose (also called dextrose),
fructose (fruit sugar) and
galactose (found in milk sugar).
- When two monosaccharides are combined, it is called a disaccharide.
Examples of disaccharides in food include
sucrose (found as table sugar, cane sugar, brown sugar, maple syrup and honey, sports drinks, gels and blocks),
lactose (naturally found in milk) and
maltose (found in cereals and germinating seeds).
3.Simple Sugars
Monosaccharides and disaccharides are known as simple sugars.
- Polysaccharides (Complex Carbohydrates)
Complex carbohydrates are long chains of monosaccharides linked together.
Common sources of polysaccharides in food are grains such as
wheat, rice, oats, cornmeal, barley, grain products and potatoes. Maltodextrin, is also made up of multiple glucose molecules, and is found in many sports nutrition products.
Carbohydrate Sources
Carbohydrates are the most important fuel for endurance athletes. Endurance athletes should select those foods that are high in nutrients and fiber whenever possible. However, if meals and snacks are consumed close to or before training, more processed forms may be better tolerated, as well as more readily available and portable for quick fueling and refueling. Breads, Cereals and Grains Fruit Vegetables Milk and Yogurt
Carbohydrates as Energy
Each gram of carbohydrate provides four calories of energy.
For example, a medium banana has 27 grams, which provides approximately 108 calories, or enough energy for an average male athlete to run one-half mile at a fast pace.
The recommended number of grams of carbohydrate varies based on the phase of the training plan, and range from 2.3 to 5.5 grams per pound, or 5 to 12 grams per kilogram.
Dietary Fats
Dietary fats play key roles in an athlete’s diet because they transport and absorb the fat-soluble vitamins A, D, E and K. Essential fatty acids are required for biological processes such as maintaining cell membranes, and are known to have anti-inflammatory effects. Dietary fats also enhance the taste of many foods. Each type of fat has a different fatty acid structure, but they all supply the same number of calories.
Keep in mind: The sources of fats and oils in our diet can provide several types of fats, though one may predominate. For example, olive oil contains monounsaturated, polyunsaturated and saturated fat, but is over 70% monounsaturated fat, so it is classified as such.
- Saturated Fats
Sources of saturated fat include animal foods such as high-fat cuts of beef, lamb, pork, and poultry; butter; cream; full-fat and 2% milk; cheese; and full fat yogurt.
Saturated fat in a more liquid form is found in coconut and palm oil.
- Polyunsaturated Fats
Polyunsaturated fats supply omega-3 and omega-6 fats.
The omega-3 fats provide the essential fatty acid alpha-linolenic acid and are found in many varieties of fish and plant foods such as flaxseed, walnut and canola oil.
Omega-6 fats provide the essential fatty acid linoleic acid. They are found in safflower, sunflower, corn, soybean, cottonseed and sesame seed oils.
These fats are required to make substances called eicosanoids, which affect blood pressure, immunity, inflammation and contraction of smooth muscle tissue.
- Monounsaturated Fats
Monounsaturated fats are omega-9 fats and are integral to keeping the heart healthy. Because of this, monounsaturated fat is often referred to as a “good fat.”
These fats are found in foods such as olive oil, canola oil, peanuts and peanut oil, most nuts and avocado.
- Trans Fat
Trans fat is harmful to the heart and increases inflammation in the body.
Trans fat naturally occurs in small amounts in meat and dairy. However, there is also man-made trans fat, which is processed differently by the body and is very harmful. Common sources are packaged cookies, crackers, snack chips and commercial fried foods such as french fries.
Fat as Energy
Each gram of fat provides nine calories—over twice the amount of energy as carbohydrates and protein. This makes stored fats a valuable source of energy for endurance athletes.
For example, one tablespoon of oil has 14 grams of fat, which provides approximately 120 calories.
Compared to carbohydrates, fats are calorically dense.
The recommended number of grams of fat varies slightly based on the phase of the training plan, and ranges from less than .5 to .8 grams per pound, or one to two grams per kilogram.
Protein: Structure
Dietary proteins are made up of a combination of 20 different amino acids. The body is able to manufacture 11 of these non-essential amino acids.
The remaining amino acids are considered essential because they cannot be synthesized in the body at a sufficient rate.
Three important essential amino acids associated with endurance training are leucine, isoleucine and valine, which are known as Branch Chain Amino Acids (BCAA). (Some sports nutrition products contain these BCAAs and they are found in unprocessed foods as well.)
Protein Sources
Protein is required for recovery from high-intensity and endurance workouts, repair of muscle tissue, and the maintenance of a strong immune system.
Endurance athletes can easily obtain enough protein by incorporating protein-rich products into meals and snacks.
Protein can be found in both animal and plant foods.
- Animal Sources
Animal products are more concentrated sources of protein than plant sources. Some animal protein sources can also contain substantial amounts of fat and saturated fat.
Endurance athletes who consume animal products should choose lean cuts of poultry, beef, pork, fish, and lamb; lower-fat cheese, milk, and yogurt; and egg whites.
Although higher in fat content, athletes should also choose cold-water fatty fish such as tuna and salmon, as a source of healthy omega-3 fatty acids.
Higher-fat source of protein should be consumed in planned portions.
- Plant Sources
Vegetarian athletes should take care to eat ample amounts of plant protein sources to ensure adequate total protein intake.
Some of these plant sources include dried beans (such as black beans and pinto beans), soy products (such as tofu), tempeh and edamame. Lentils, split peas and nut spreads also provide protein.
Protein: Recommendations
Similar to carbohydrates, each gram of protein provides four calories of energy.
For most endurance triathletes, the recommended number of grams of protein varies based on the volume of training, and the phase of the training plan.
The recommendations range from .5–1 gram per pound, or 1–2.2 grams per kilogram. (There are additional recommendations for triathletes who are on a calorie-restricted diet.)
Nutrition Periodization
The macronutrient intake for endurance athletes should vary throughout the year due to the changes in duration and intensity of training.
Nutrition periodization: Fluctuating macronutrient intake to meet the energy demands based on the phase of training.
The Components of Total Daily Energy Expenditure
- Resting Metabolic Rate
Resting Metabolic Rate (RMR) is the amount of energy that is needed to keep the body functioning during rest. It includes energy needed to breathe, as well as the energy needed for the heart and brain to function. RMR generally accounts for 60–75% of the total daily energy expenditure (depending on the daily level of physical activity).
There are many factors that determine a person’s RMR, including (but not limited to) age, gender, body composition, height and weight.
- Non-Exercise Activity Thermogenesis
Non-exercise activity thermogenesis (NEAT) is the amount of energy that is expended for normal activities of daily living, excluding sleeping, eating and exercising.
In fact, as you take this course, you are expending non-exercise activity thermogenesis calories!
- Thermic Effect of Food
The thermic effect of food (TEF) is the amount of energy that is needed to digest and absorb food.
TEF contributes to less than 10% of Total Daily Energy Expenditure.
4. Exercise Energy Expenditure Energy expenditure (ExEE) is any energy that is expelled during exercise. ExEE will vary greatly based on the duration, intensity and type of exercise.
This component generally makes up about 30% of the Total Daily Energy Expenditure, but for endurance athletes it can account up to 80%, depending on the duration and intensity of exercise.
Factors Affecting Energy Needs
There are many factors that affect an athlete’s resting metabolic rate and his or her total daily energy expenditure.
To learn more about these factors, let’s assess the energy needs of Jane. Jane is a female in her mid-thirties living in Houston, Texas. She is currently training for her first IRONMAN.
- Body Weight and Height
Body weight and height are both factors contributing to Jane’s RMR. The more body mass, the greater the RMR.
Additionally, energy expended during weight-bearing activities increases proportional to body mass. (Body mass takes into consideration the athlete’s weight and height.)
- Body Composition
Body mass composition comprises fat-free mass and fat mass.
Fat-free mass (or lean body mass) includes muscle, bones, organs, tissue and water. Fat mass includes adipose tissue, intramuscular fat and plasma fats. By nature, males have a higher percentage fat-free mass than females.
Fat mass includes adipose tissue, intramuscular fat and plasma fats. On average, males have a higher RMR due to the larger percent of fat-free mass.
Qualified health professionals can assess body composition by using indirect measures such as skin fold testing and bioelectrical impedance analysis (BIA).
- Gender
Jane’s gender will affect her RMR.
Males tend to have a higher RMR (up to 10%) than females of similar age and level of fitness. This is primarily due to the body composition differences between males and females. On average, females have a lower RMR due to a larger percent body fat and smaller muscle mass.
- Age
This will also affect Jane’s RMR, because a triathlete’s caloric needs decline with age. This is due to a loss in fat-free body mass that occurs naturally over time.
It has been estimated that RMR decreases approximately 2% per decade in healthy adult women and approximately 3% per decade in healthy men.
- Daily Caloric Consumption
To maintain her present body weight, Jane’s calorie intake must be equal to the calories she expends.
To gain weight, Jane’s caloric intake must exceed her caloric expenditure. To lose weight, her caloric intake must be less than the energy she expends.
Metabolic adaptations occur when athletes are calorie deficient or when they restrict calorie intake. The body compensates by using the available energy sources more efficiently. This effect can lower the RMR.
- Climate and Altitude
Environmental factors can also influence an athlete’s RMR.
Warm Weather: Individuals living in tropical climates average 5–20% higher RMR than counterparts in more temperate regions. Exercise performed in hot weather also causes about a 5% elevation in oxygen intake (and correlated energy expenditure), compared to the same work performed in a thermoneutral climate. This increased energy expenditure is due to an elevated core temperature and additional energy required for sweat gland activity.
Cold Weather: Depending upon an athlete’s body fat content and type of protective clothing, cold environments can increase energy expenditure required to regulate body temperature. Extreme cold causes shivering, a response meant to generate enough heat to maintain a stable core body temperature. This response can triple the athlete’s RMR.
Altitude: During the first few days at altitude, resting metabolic rate can increase by as much as 40%. However, it gradually drops to approximately 15% above sea-level values. The increase in RMR may increase the athlete’s overall energy needs by 200–300 calories per day.
- Economy of Movement
As you may recall from the Exercise Science module, because oxygen utilization is directly tied to ATP and heat production, the measurement of oxygen consumption is used to quantify energy expenditure.
As movement economy increases, the amount of oxygen required to perform the exercise, and therefore the amount of energy expended, decreases. Although this does not directly affect the RMR, it does play a factor in the overall daily energy expenditure.
Estimating Total Daily Energy Expenditure using Equipment
The RMR test, using portal equipment available at research labs and fitness centers, is non-invasive, time-efficient, well validated and widely available.
It is the most accurate method because it measures oxygen uptake which directly correlates to energy expenditure.
This direct method is recommended for endurance athletes who struggle with weight management issues.
Estimating Total Daily Energy Expenditure using Body Weight
The simplest method of estimating daily calorie needs is to calculate the calories per pound (or kilogram).
This method is based on weight and training level, and takes into account the RMR, daily energy needs and additional energy needed for exercise.
To use this formula, you must know the athlete’s weight, the level of exercise intensity and/or the duration of exercise.
The Mifflin St. Jeor Equation
The Mifflin St. Jeor Equation predicts TDEE by estimating an athlete’s RMR and multiplying the RMR by a specified physical activity level factor (PAL).
Calorie Burning Data
The calorie burning data collected from a heart rate monitor or power meter can also be used to determine that day’s TDEE.
The Mifflin St Jeor equation estimates RMR. You can then multiply this by a factor of 1.2 to 1.3 for a sedentary job, or 1.4 to 1.5 if you have an active job.
Then add in the calories burned during training.
Role of Water
Water plays many vital roles that directly affect the athlete’s health and performance.
Water is also the main component of blood, which is responsible for transporting nutrients (such as glucose), gases (such as oxygen) and waste.
When the body is fully hydrated, 90% of blood is water!
Water dissipates heat through the evaporation of sweat from the skin, cooling the body and maintaining its core temperature.
Water removes lactic acid from exercising muscles, and muscle glycogen holds water, which can be an advantage to well-hydrated athletes.
Water is also responsible for lubricating joints, moistening tissue and protecting body organs.
Balancing Water Gain and Loss
The athlete must regain fluid balance by replacing water and electrolytes lost during the sweating process.
Water balance depends on the net difference between water gained and water lost.
Because endurance athletes are particularly at risk for excessive loss of water during exercise, coaches should encourage athletes to carefully monitor their hydration status and replenish fluids to meet physiological needs.
Fluid Loss
Daily water balance depends on the net difference between water gained and water lost. Athletes gain water from the consumption of foods and fluids.
Fluids are lost through sweat, oxidation of carbohydrates, proteins and fats, respiration (breathing), and the output of body waste (urine and feces).
One study found that during an IRONMAN, the average athlete’s sweat rate for the bike leg is .81 liters per hour, with ranges from .47–1.08 liters. The average sweat rate for the run is 1.02 liters per hour with ranges from .4–1.8.
Even small changes in temperature can increase the amount of sweat produced. Therefore, the athlete’s goal is to take in adequate amounts of fluid and electrolytes to compensate for the fluid and electrolyte losses.
Sodium
99% of sweat is water; the other 1% is electrolytes. Sodium is an especially critical electrolyte, particularly for endurance athletes with a high sweat rate, because compared to the other electrolytes, it has the highest concentration in sweat.
Athletes can lose between 115–2,300 milligrams of sodium per liter of sweat, and athletes with higher sweat rates or sweat sodium concentrations may exceed this range. To put this in perspective, one teaspoon of table salt has approximately 2,000 milligrams (mg) of sodium.
Note: Sodium and salt are not interchangeable. Dietary salt, or table salt, is only made up of 40% sodium. The other 60% of salt is chloride.
Other Important Electrolytes
Potassium controls fluid and electrolyte balance, assists in the conduction of nerve transmission and helps move glucose into the cell.
Magnesium regulates muscle relaxation and aids electrolytes through the cell membranes.
Calcium plays a role in skeletal muscle contraction, nerve impulse transmission and the synthesis and breakdown of muscle and liver glycogen.
To perform optimally, athletes must find ways to replenish these valuable electrolytes.
Factors that Affect Fluid Needs
- Sport
Even during swimming the body loses water through sweat and respiration. This water loss is increased when swimming in warm bodies of water, and in a wetsuit. Generally, sweat rates while cycling tend to be less than sweat rates while running due to the cooling effect of wind.
Running usually elicits a higher sweat rate than swimming or biking, because of heat production and/or exercise intensity.
- Skin and Clothing
Both wet skin and dehydration reduce sweat rates.
Because different materials absorb water at different rates, athletes should be encouraged to wear clothing that allows for heat dissipation and sweat evaporation. Coaches should also encourage athletes to wear light-colored clothing when training and racing in warm climates to reflect heat rays away from the body.
Heavy impermeable clothing, such as wetsuits, also increases sweat rate and inhibits the dissipation of heat. Athletes who wear wetsuits and swim in warmer water should allow for an increase in fluid and electrolyte consumption. Moisture-wicking materials worn close to the skin transfer heat and moisture from the skin to the environment, particularly in hot weather.
Wicking material is also beneficial during cold weather because dry clothing reduces the risk of hypothermia.
- Environment
Athletes exercising in warm to hot and humid climates, as well as indoors on treadmills or trainers may have a higher sweat production. Coaches should encourage athletes to monitor hydration to ensure adequate fluid intake and slightly increase sodium intake to replenish lost electrolytes.
In temperate and cooler environments, there is a reduced need for evaporative cooling. Sweat losses are relatively small but there are still respiratory fluid losses. Athletes should monitor their sweat rates at various temperatures to prepare for various race conditions and adjust their race plan.
- Heat Acclimatization and Altitude
Heat acclimatization improves the athlete’s ability to reabsorb sodium and chloride and reduces the sodium concentration in sweat.
Complete heat acclimatization requires up to 14 days. Therefore, athletes planning to race in hot environments (but living in cool climates) should be encouraged to allow extra time to acclimatize prior to the race.
Athletes living, training and racing at altitude greater than 2,500 m (8,200 ft) have increased fluid losses not associated with exercise.
According to the American College of Sports Medicine, respiratory losses may be as high as 1.9 Liters (2 quarts) in males and .85 Liters (28 ounces) in females per day. This means, to promote optimal kidney function, athletes should consume three to four liters of fluid per day, at high altitude.
Maintaining hydration by matching fluid intake with water lost through sweat is one of the most critical factors in preventing heat illness. Choosing clothing and equipment that is light-colored, loose-fitting, and moisture-wicking will help keep an athlete cool.
Athletes should progressively increase the intensity and duration of their training sessions to become fully acclimated to their environment.
- Level of Fitness and Diet
One effect of training is an increase in efficiency at regulating core temperature.
Although sweat rate is variable, training can increase the density of sweat glands producing a greater amount of sweat. Trained athletes also begin sweating sooner than untrained athletes. This is beneficial since evaporation of sweat cools the skin.
Athletes who consume more dietary sodium tend to lose more sodium in their sweat than those with a lower sodium intake.
- Body Weight, Gender, and Age
Women have more heat-activated sweat glands than men, but sweat less profusely. Women also begin sweating at a higher skin and core temperature.
Older athletes may have age-related blunting, which is a reduced sensitivity to thirst. These athletes should be encouraged to monitor fluid intake and create plans for drinking fluids while exercising based on set time intervals. Age does not have an effect on sweat electrolyte concentrations.
Guidelines for Fluid and Sodium Needs
- Fluid Replacement Before Exercise
Athletes should consume fluids several hours before exercise. At least four hours before exercise, athletes should drink about five to seven milliliters per kilogram body weight of water or a sport beverage. (This is equivalent to approximately one fluid ounce per each 10 pounds of body weight.)
If profuse sweating is expected, or if there is still a deficit in fluid balance, athletes should drink an additional three to five milliliters per kilogram body weight within two hours before exercise. (This is equivalent to approximately 0.6 fluid ounces per each 10 pounds of body weight.)
It is important to consume the fluids slowly, rather than all at once.
Consuming beverages with sodium will help
- Fluid Replacement During Exercise
During exercise, the goal of drinking fluids is to avoid dehydration. This is accomplished by replacing fluids based on the athlete’s sweat rate and according to his or her level of thirst. Consuming fluids in excess of sweat rate should be discouraged.
To increase gastric emptying, athletes should consume an average of four to eight ounces of fluid every 15–20 minutes of exercise. For example, if the athlete’s sweat rate was 16 ounces (480 ml) per hour, he or she would try to drink four ounces (120 ml) every 15 minutes.
The amount of fluid intake, as well as the rate of intake, will depend on the individual’s tolerance, the type of activity and the intensity of the activity.
- Fluid Replacement After Exercise
After exercise, the athlete should drink adequate fluids to replace sweat loss.
Coaches should encourage athletes to consume approximately 16 to 24 ounces (450 to 675 milliliter) fluid for every pound (0.5 kg) of body weight lost during exercise.
To promote rehydration, fluids should be consumed within three hours of exercise. Consuming beverages and snacks with sodium will also help restore hydration levels by stimulating thirst and retaining fluids.
Athletes needing rapid and complete recovery from excessive dehydration can drink approximately 1.5 L of fluid for each kilogram of body weight lost. (This is equivalent to 23 fluid ounces per pound of body weight lost.)
Optimal Intake
Before exercise: consume beverages with sodium (460–1150mg/liter) and/or sports nutrition products and sodium-containing foods to help to stimulate thirst and retain the consumed fluids.
During exercise: consume 500–700 mg sodium per liter or 32 fl. oz.
After exercise: consume foods and fluids that contain sodium to facilitate rehydration. This results in less urine production and improved hydration.
Sports Drinks and Nutrition Products
During exercise, coaches should encourage athletes to obtain the necessary sodium using sports drinks, and products with sodium and salty foods.
For example, sports drinks typically contain 500mg–700mg sodium per liter (33 fluid ounces).
Factors Affecting Fluid Absorption
Fluids must be absorbed through the intestines to be moved into the cells.
Factors that reduce gastric emptying time and intestinal absorption will negatively affect the athlete’s performance.
Calculating Sweat Loss
Sweat rate calculations determine how much fluid an athlete should consume during a training session by calculating the amount of fluid that is expelled through sweat during exercise.
Sweat rate is specific to the discipline being tested, so athletes should conduct this test for swimming, biking and running.
The following screens will explore how coaches and athletes can determine sweat rate. This resource covers how to calculate sweat loss. Use this as a companion resource as you continue through the next few screens of the course. You may also use this to determine the sweat rates of your athletes.
Rehydrating after Exercise
It’s just as important to hydrate after exercise as it is before and during exercise.
To adequately rehydrate, athletes should consume approximately 16 to 24 fluid ounces for every pound or 1.5 liters per kg body weight lost during exercise.
These fluids should be consumed within three hours of exercise. Beverages and snacks with sodium will also help restore hydration levels by stimulating thirst and retaining fluids.
Athletes needing rapid and complete recovery from excessive dehydration can drink approximately 1.5 liters of fluid for each kilogram of body weight lost. This is equivalent to 23 fluid ounces per pound of body weight lost.
Causes of Dehydration
Dehydration can be mild, moderate or severe, with health and performance risks increasing with progressive dehydration.
Dehydration can also be cumulative and add up over the training session or event. This is especially true when the interval between training sessions is inadequate to fully hydrate.
Engaging in vigorous exercise (especially in hot climates) with inadequate hydration is the most common cause of dehydration.
Other common causes include
intense diarrhea,
vomiting,
fever and
excessive sweating.
Signs of Dehydration
Signs of dehydration include
thirst, flushed skin, premature fatigue, increased body temperature, faster breathing and pulse rate, an increased perception of effort and a decreased exercise capacity. Other sign (that may occur later) include
dizziness, dark colored urine, chills, muscle cramping, increased weakness and labored breathing during exercise.
