Sports Nutrition for Peak Performance. We have been discussing basic concepts of nutrition: - Food choices and nutritional guidelines - Food choices and

Sports Nutrition for

Peak Performance

We have been discussing basic concepts of nutrition:

- Food choices and nutritional guidelines - Digestion - Carbohydrates, lipids, and proteins - Energy balance and body composition - Vitamins - Water and mineral balance

We have been discussing basic concepts of nutrition:

- Food choices and nutritional guidelines - Digestion - Carbohydrates, lipids, and proteins - Energy balance and body composition - Vitamins - Water and mineral balance

For the rest of this course, we will discuss some specific applications of those concepts:

- Sports nutrition - Nutrition in pregnancy and various life stages - Food safety and technology - Global nutrition

As we have discussed many times, maintaining an active lifestyle is an important part of maintaining energy balance, normal weight, and healthy eating habits.


Humans evolved for both intensive short-term (anerobic) exercise such as sprinting to overtake prey, and long-term (aerobic) endurance exercise such as chasing prey over long distances.

These adaptations include how the body obtains various nutrients, as well as how the body uses these nutrients under different physiological conditions.


Thus, nutrition and physical activity are intricately linked and must be considered together:

- changes in physical activity result in changes in nutritional needs

- changes in nutrition are reflected in changes in physical activity

Nutrition in Exercise and Sports Performance

Unfortunately, in modern life our physical activity and our our dietary habits have not remained in balance.



We eat more food and more types of food, particularlyhigh-calorie carbohydratesand fats.



We eat more food and more types of food, particularlyhigh-calorie carbohydratesand fats.

At the same time, we have become more sedentary, getting less exercise in both duration and intensity. The result it that we are becoming increasingly out-of-shape physically and increasingly obese, and we are experiencing more health problems because of these.


To combat that, a variety of recommendations have been developed through both public and private organization to encourage us to get adequate exercise and to develop eating habits which are better aligned with modern lifestyles.

Exercise places strong demands on the body to provide

- Energy for strenuous and/or sustained muscle use - Building blocks for muscle and bone growth - Pathways to remove waste products of activity


We need to start out with a review of the structure and contraction of muscles and muscle cells.

Nutrition in Exercise: Muscle


In a muscle such as your rectus femoris or gastrocnemius (both in the lower limb)the muscle cells (“myocytes”, “fibers”) areall arranged in the same direction so they all pull in the same direction.



In a muscle such as your rectus femoris or gastrocnemius (both in the lower limb)the muscle cells (“myocytes”, “fibers”) areall arranged in the same direction so they all pull in the same direction.

Within each cell are bundles of contractile proteins called myofibrils.There are also many mitochondria.


Those myofibrils are composed of thousands of smaller structures called myofilaments which slide past each other during contraction. That requires the release of large amounts of calcium inside the cell, and it requires a large amount of energy.


Those myofibrils are composed of thousands of smaller structures called myofilaments which slide past each other during contraction. That requires the release of large amounts of calcium inside the cell, and it requires a large amount of energy.

You will recall that energy for all cellular processes, including muscle contraction, is provided by a molecule calledadenosine triphosphate (ATP).


Muscle cells contain a lot of pre-formed ATP.

Nutrition in Exercise: ATP

However, in exercise they quickly deplete all of that stored ATP. They have a related molecule calledcreatine phosphate (CP) which can be used to quickly make more ATP, but that too will be used up in just a few seconds of strenuous exercise.

(Your book calls this the “ATP-CP Energy System”)

Once ATP and CP are depleted, your muscle cells begin to break apart glycogen to release glucose molecules.



Through glycolysis, each molecule of glucose is converted to two molecules of pyruvate, forming two molecules of ATP in the process. This does not require oxygen, that is, it is anaerobic.

Glucose

2 Pyruvate

ATPATP



Through glycolysis, each molecule of glucose is converted to two molecules of pyruvate, forming two molecules of ATP in the process. This does not require oxygen, that is, it is anaerobic.

In the absence of oxygen, pyruvate is converted to lactic acid, which interferes with contraction. It must be removed from the muscle cells and sent to the liver.

Glucose

2 Pyruvate

ATPATP

2 Lactic Acid

(Your book calls this the “Lactic Acid Energy System”)


This anaerobic system of glycolysis can produce a small amount of ATP quickly, so it is sufficient for short periods of exercise. However, it can not produce enough to sustain long-term exercise. For that, oxygen is needed.

Oxygen is delivered to the muscle cells in the blood, and some was stored by attachment to the molecule myoglobin.


In the presence of oxygen, the pyruvate is converted to a molecule called acetyl CoA. Within the mitochondria, this is sent into a series of reactions called the Kreb’s Cycle or Tricarboxylic Acid Cycle, which generates another 18 molecules of ATP from each acetyl CoA, or 36 molecules of ATP from each glucose molecule.

Glucose

2 Pyruvate

ATPATP

2 Acetyl CoA

36 ATP6 CO2 6 O2


In the presence of oxygen, the pyruvate is converted to a molecule called acetyl CoA. Within the mitochondria, this is sent into a series of reactions called the Kreb’s Cycle or Tricarboxylic Acid Cycle, which generates another 18 molecules of ATP from each acetyl CoA, or 36 molecules of ATP from each glucose molecule.

While that produces a lot more ATP than glycolysis alone, it is much slower

Glucose

2 Pyruvate

ATPATP

2 Acetyl CoA

36 ATP6 CO2 6 O2

(Your book calls this the “Oxygen Energy System”)


Another advantage of the Kreb’s Cycle is that it can also be used to produce energy from fats (and, if absolutely necessary, proteins) through acetyl CoA.

Glucose Pyruvate Acetyl

CoAATP

CO2 O2

(Amino Acids)

(Proteins)

Fatty Acids

TriglyceridesGlycogen


Another advantage of the Kreb’s Cycle is that it can also be used to produce energy from fats (and, if absolutely necessary, proteins) through acetyl CoA.

Glucose Pyruvate Acetyl

CoAATP

CO2 O2

(Amino Acids)

(Proteins)

Fatty Acids

TriglyceridesHowever, it takes a longer time for the body to mobilize fats and send them to the muscle cells, so at least the early stages of exercise depend on the muscle cells’ store of glycogen.

Glycogen


During exercise, of course, all of these systems of producing energy (in the form of ATP) are used by muscle cells as long as glycogen is available.


During exercise, of course, all of these systems of producing energy (in the form of ATP) are used by muscle cells as long as glycogen is available.

Eventually, the stored glucogen will be depleted and muscle fatigue occurs.

The muscle cells can obtain some glucose from the blood, but this is not enough to sustain prolonged exercise.


Endurance training increases the number of mitochondria within the muscle cells, and it increases their ability to store glucose as glycogen and to store oxygen attached to myoglobin, so it

- Decreases reliance on anaerobic systems- Extends availability of glycogen- Delays fatigue


In reality, we have been oversimplifying things a bit.It turns out that not all muscle cells are the same.

All of your skeletal muscles (the organs, such as your biceps brachii or trapezius) have two types of muscle cells (“myocytes” or “fibers”)

Nutrition in Exercise: Muscle Cells

1. Fast twitch cells have large amounts of glycogen but few mitochondria and small amounts of myoglobin. They can generate ATP quickly by the anaerobic pathway and contract quickly, but they fatigue easily.

In reality, we have been oversimplifying things a bit.It turns out that not all muscle cells are the same.

All of your skeletal muscles (the organs, such as your biceps brachii or trapezius) have two types of muscle cells (“myocytes” or “fibers”)

2. Slow twitch cells have moderate amounts of glycogen, many mitochondria, and large amounts of myoglobin. They generate a lot more ATP but do it more slowly by the aerobic pathway, contracting more slowly, but fatiguing less easily.


Exercise training can change the proportion of slow-twitch and fast-twitch cells in your muscles.

Consequently, you can make your muscles more efficient for either short-term or long-term exercise.



Production of ATP for energy (from creatine phosphate, through glycolysis, and through the Kreb’s cycle) is certainly an important part of nutrition for exercise, but of course it is not the only thing which is important.


Production of ATP for energy (from creatine phosphate, through glycolysis, and through the Kreb’s cycle) is certainly an important part of nutrition for exercise, but of course it is not the only thing which is important.

During exercise you need to: - consume adequate calories for your energy needs - consume adequate amino acids to maintain proteins - consume adequate vitamins and minerals - maintain fluid balance & avoid dehydration

Long-term, you also need to: - maintain proper body mass and body fat - recover from muscle damage from exercise


The most important nutritional concern of exercise and athletic performance is adequate energy intake from two primary sources: - carbohydrates - lipids


The most important nutritional concern of exercise and athletic performance is adequate energy intake from two primary sources: - carbohydrates - lipids

These are important both - short term to provide glucose and fatty acids for immediate use, and - long term to provide the molecules needed to replenish glygocen and triglycerides.

Nutrition in Exercise: Carbohydrate

For most athletes, smaller more frequent meals containing complex carbohydrates works best.

These take longer to be digested to release mosaccharides, slowing their absorption from the intestine into the blood and producing a more stable level of glucose in the blood.

This helps increase glycogen storage in liver and muscle cells as well as ensuring that a continuous supply of glucose is availabe in the blood for immediate energy needs.

Food with complex carbohydrates have the additional advantage of often also providing vitamins and minerals.

If you start early enough, you can significantly increase the amount of glycogen stored in your muscles by a process called carbohydrate loading in which you alternate shorter, less intense periods of exercise with high carbohydrate meals.


If you start early enough, you can significantly increase the amount of glycogen stored in your muscles by a process called carbohydrate loading in which you alternate shorter, less intense periods of exercise with high carbohydrate meals.

Since the muscles of most athletes have enough glycogen to last at least 60-90 minutes, this is only effective for periods of activity longer than that.


Two to four hours before strenuous exercise, mealsshould contain up to 65% oftheir calories as complex carbohydrates with low or moderate glycemic indices, and 10% to 20% each from lipids and proteins.




Just before exercise, eat easily digestable carbohydrates with higher glycemic indices.


Just before exercise, eat easily digestable carbohydrates with higher glycemic indices.

During exercise, eat or drink small amounts (large meals can cause digestiveproblems) of foods with high glycemic indices.


Immediately after strenuous exercise you should begin eating foods withmoderate to high glycemic indicesto immediately begin to replenishglycogen, and you should continueto eat carbohydrates for a few hours.


Immediately after strenuous exercise you should begin eating foods withmoderate to high glycemic indicesto immediately begin to replenishglycogen, and you should continueto eat carbohydrates for a few hours.

Of course, exercise causes significant loss of water and minerals, so it is important to also remain hydrated during exercise to maintain fluid balance. Without this, your muscle cells can not effectively use glycogen, produce energy through glycolysis or the Kreb’s cycle, or remove waste products such as lactic acid or CO2.


While carbohydrates are critical to peak performance during exercise, they are not the only important nutrients.

Fats, proteins, vitamins, and minerals are also involved.

Nutrition in Exercise:

At all times, carbohydrates and fats are the two primary fuels: fats should contribute 20%-30% of calories.

Glucose

Pyruvate

Acetyl CoA

ATP

CO2

O2

Fatty Acids


Nutrition in Exercise: Fats

At all times, carbohydrates and fats are the two primary fuels: fats should contribute 20%-30% of calories.

Glucose

Pyruvate

Acetyl CoA

ATP

CO2

O2

Fatty Acids


This is particularly true during exercise. In low-intensity exercise after glycogen is depleted from cells, fats often become the primary fuel source if carbohydrates are not consumed.


However:

- fat is digested and absorbed more slowly than carbohydrates with high glycemic indices

- fatty acids are not transported as easily in the blood as glucose

- fatty acid are not absorbed from the blood into muscle cells as easily as glucose


However:

- fat is digested and absorbed more slowly than carbohydrates with high glycemic indices

- fatty acids are not transported as easily in the blood as glucose

- fatty acid are not absorbed from the blood into muscle cells as easily as glucose

Thus, fatty acids are more difficult for muscle cells to use,

but


Like any other times: dietary fats during exercise should

- include monounsaturated & polyunsaturatedfatty acids

- minimize trans fatty acids

- include omega-3 and omega-6 fatty acids

- be part of foods that also include proteins, vitamins, and minerals


A word of caution:

Fat is sometimes erroneously seen by athletes as something “bad” to be avoided in the diet and removed from the body.

While excess fat is indeed unhealthy, too little body fat is also unhealthy

Fat: Provides fatty acids for energy Protects internal organs Insulates against heat loss Regulates a number of hormones Stores some vitamins Forms phospholipids for cell membranes


The American Dietetic Association recommends that

- men have 15-18% body fat - women have 20-25% body fat. but - healthy male athletes can have 5-12% body fat - healthy female athletes can have 10-20% body fat


A group of compounds called thermogenics or “fat burners” are available.

These may include the stimulant and appetite suppressant ephedrine or similar chemicals which have been linked to high blood pressure, heart disease, stroke, and occasionally death.


In addition to carbohydrates and fats, proteins are important for peak performance during exercise.

Nutrition in Exercise: Proteins

In addition to carbohydrates and fats, proteins are important for peak performance during exercise.

However, it is a misconception that a high-protein diet will significantly enhance performance in most cases.

- Proteins are not a significant source of calories during exercise

- Excess amino acids must be broken down in the liver and their amino groups disposed of as urea in the urine. This increases urine production, pulling water out of the body and leading to dehydration.

- Excessive protein intake, such as through supplements, can overload this system and cause kidney failure


Dietary proteins are needed primarily to

- replace muscle proteins damaged during exercise

- build new proteins as muscle cells grow during training

Note that the key to the latter is the training: Additional dietary protein alone will not increase muscle mass without the stimulus of strength training or endurance training.


As noted a couple of weeks ago, the amount of protein in the diets of most Americans greatly exceeds the amounts needed, so most people usually get enough protein in their diets for moderate exercise.

Athletes in training for suchevents as marathons, strengthtraining, elite-level sports, etc.may need to increase theirdietary protein, up to doublethe normally recommendedamounts


Athletes in training for such events as marathons, strength training, elite-level sports, etc. may need to increase their dietary protein, up to double the normally recommended amounts.

These should come from the“high quality” protein foods wediscussed earlier: Lean meats, poultry, fish Low fat dairy products Legumes Grains Eggs


Proteins also play an important role after exercise:

Combined intake of carbohydrates and proteins increases the synthesis of glycogen more than the intake of carbohydrate alone.

Recommendation: 1 g protein per 2.5 g carbohydrateAs always: foods containing both such as dairy products, grains, or legumes are more effective than individual supplements.


Many reactions in the body during exercise need vitamins:

- Vitamin A helps regulate protein synthesis & cell growth - Vitamin D is necessary for healthy bones & muscles - Vitamin K regulates bone growth & blood clotting - Vitamins E and C are antioxidants to remove waste products of cellular metabolism - Many B vitamins are cofactors of the enzymes needed to extract energy from carbohydrates and fats - Many B vitamins are need for to extract and store the energy released from carbohydrates and fats

Nutrition in Exercise: Vitamins

Fortunately, the amounts of vitamins in a normal diet are sufficient to meet the needs of all but the most highly trained athletes.

Nutrition in Exercise: Vitamins

Of more concern to athletes are minerals, since these are necessary for proper fluid balance and for the health and normal functions of bones, muscle, nerves, and blood. They can also be lost in the increased amounts of sweat and urine which can occur during strenuous activity.

Nutrition in Exercise: Minerals

- Iron is needed for hemoglobin for oxygen transport - Calcium, potassium, and magnesium regulate nerve function and muscle contraction - Calcium and phosporus provide strength to bone - Sodium, chloride, and potassium regulate fluid movement among compartments


As with vitamins, the amounts of minerals in healthy diets are sufficient to meet most of the needs of all but the most highly trained athletes.

The most common problem arises from excessive sweating which can cause the loss of chloride, sodium, potassium, calcium, magnesium, and smaller amounts of other minerals.


As with vitamins, the amounts of minerals in healthy diets are sufficient to meet most of the needs of all but the most highly trained athletes.

The most common problem arises from excessive sweating which can cause the loss of chloride, sodium, potassium, calcium, magnesium, and smaller amounts of other minerals.

Fortunately, these can be quickly replenished from a variety of foods, and sports drinks are specifically formulated to provide adequate amounts.


Although the needs of these various nutrients are important components of maintaining healthy nutrition during exercise and strenuous activity, the most critical component for most athletes is maintaining water and fluid balance.

Nutrition in Exercise: Fluids

Movement among

Forms urine

Forms tears, saliva, CSF, synovial fluid, semen, lymph, etc.


Water = more than 60% of total body mass

3 major compartments: Plasma ~8% of body water Interstitial ~25% of body water Intracellular ~65% of body water

Many smaller compartments: ~ 2% Urine, Lymphatic fluid, Cerebrospinal fluid, Saliva, Synovial fluid, Digestive system contents, Semen, Respiratory system fluids, Peritoneal fluid, Tears, Occular fluids, Pericardial fluid, Pleural fluid, etc.


These fluid compartments are in equilibrium with each other


Water intake is primarily through foodand drink. Some water is gained from metabolic processes like the synthesis of proteins, lipids, and carbohydrates.

Water output is primarily through urine,sweat, transcutanous loss, respiration, and feces. These are obviously affected by such things as temperature, exercise, humidity, etc.



During exercise, additional water is lost through sweatingand must be replaced.

During exercise, additional water is lost through sweatingand must be replaced.


Sweating is necessary to coolthe body and remove the extraheat produced by the muscles.

The water in sweat is pulled from the plasma, which pulls water from allother compartments.


It must then be replaced through the digestive system.

Sweating starts early in exercise and continues well after you finish exercising, so you should consume water before, during, and after exercise. The goal should be to drink fluids at the same rate you are losing them.


Sweating starts early in exercise and continues well after you finish exercising, so you should consume water before, during, and after exercise. The goal should be to drink fluids at the same rate you are losing them.


Since minerals such as sodium, chloride, and potassium are also lost through sweat, in prolonged exercise you should also take in minerals to replace those.



Inadequate fluid intake can lead to dehydration

Supplements to enhance athletic performance, or ergogenic supplements, are a multi-billion dollar business in the United States

- Provide energy, both short-term and long-term - Provide carbohydrates, vitamins, minerals - Build muscle mass - Strengthen muscles - Strengthen bones, joints, ligaments, tendons - Enhance post-exercise recovery

Nutrition in Exercise: Supplements

Supplements to enhance athletic performance, or ergogenic supplements, are a multi-billion dollar business in the United States

- Provide energy, both short-term and long-term - Provide carbohydrates, vitamins, minerals - Build muscle mass - Strengthen muscles - Strengthen bones, joints, ligaments, tendons - Enhance post-exercise recovery


Some are beneficial, some are not.


Common ergonomic supplements include:

1. Antioxidants such as ascorbic acid (vitamin C) tocopherols (vitamin E)

carotenoids (vitamin A) glutathione melatonin lutein



2. Amino acids and proteins - muscle mass - muscle repair



3. Caffeine - stimulant - endurance



4. Carnitine - fat transport - enhanced nerve function



5. Co-enzyme Q - enhanced aerobic performance - antioxidant

http://www.puritan.com/coenzyme-q-10-055/q-sorb-co-q-10-200-mg-002092?NewPage=1



6. Ephedrine - stimulant - weight loss



7. Androgens (hormones related to testosterone) such as androstenedione dehydroepiandrosterone dihydrotestosterone

Nutrition in Exercise:

In general, however, nutrition in exercise boils down to a eating a healthy diet with four essential priorities:

1. Adequate fuel intake (carbohydrate, lipid) 2. Adequate protein intake 3. Adequate vitamin and mineral intake 4. Adequate fluid intake

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Sports Nutrition for Peak Performance. We have been discussing basic concepts of nutrition: - Food choices and nutritional guidelines - Food choices and