Lecture 10A: Chapter 10

LECTURE 10A: Chapter 12
Nutrition and Physical Activity: Keys to good health

FORUM:

1. This week we will be discussing physical activity. Although the focus of this course has been nutrition, there are many factors that play a role in living a healthy life, physical activity being one of them. Throughout the course the focus on healthy eating has been on making sure that your eating is both enjoyable and sustainable. It is no different when it comes to exercise. We need to find the joy in movement to make sure it is something that is enjoyable and sustainable. Below is a fun video that one of the Exercise and Movement Science students put together on how different people find joy in movement. How do you find joy in movement?

2. What did you read in Chapter 12 that was new or interesting? How can you apply this information?

First look through the major headings of this lecture.

I Benefits of Exercise
II 4 Components of Fitness & Guidelines
III Benefits of regular AEROBIC activity
IV Benefits of regular ANAEROBIC activity
V Energy Use
VI Fuel Use during AEROBIC activity
VII Fuel Use during ANAEROBIC activity
VIII Protein as Fuel
IX Fluids and Temperature
X Sports Drinks

Now use the following information to fill in Ch. 12 lecture outline.

I Benefits of Exercise

Your lecture outline lists the following benefits:

improved mental outlook
feeling of vigor
sound sleep
reduced body fat
greater bone density
reduced risk of heart disease & some cancers
improved blood sugar control

I find that often times people's primary reason for exercising is to reduce body fat. Usually people measure their progress of reducing body fat by the scale, which does not distinguish between muscle and fat. When the number on the scale does not go down, or maybe even initially goes up, people are not motivated to continue exercising. This is a shame because more research is showing that fitness is more important than fatness. So you don't necessarily need to lose body fat to gain benefits.

Nancy Clark, the author of, "Nancy Clark's Sports Nutrition Guidebook" discusses the myth that starting an exercise plan leads to a reduction of body fat. The reason why exercise alone with no dietary changes does not necessarily result in a reduction of body fat is because appetite tends to keep up with Calories burned through exercise. She states that this is especially true for women. We also tend to reward ourselves with food after exercise.

II 4 Components of Fitness

flexibility- the capacity of the joints to move through a full range of motion; the ability to bend and recover without injury.
muscular strength- the ability of muscles to work against resistance.
muscular endurance- the ability of a muscle to contract repeatedly within a given time without becoming exhausted.
cardio-respiratory endurance- the ability to perform large-muscle dynamic exercise of moderate-to-high intensity for prolonged periods.

Physical Activity Guidelines for Americans

The following graphic illustrates the physical activity guidelines for Americans.

Are you currently meeting the above guidelines? Do you perform strength training activities at least 2 times per week? Do you spend at least 150 minutes of moderate intensity aerobic activities per week? If not, what is a small realistic goal you can set for yourself to improve your activity?

III Benefits of regular AEROBIC (use oxygen) activities

Aerobic activities like jogging or brisk walking lead to lung/respiratory muscles getting stronger so you can breathe in more oxygen. Heart/cardiac muscles also get stronger so there is more oxygen rich blood pumped by the heart for every beat. (Cardiac Output increases).

With regular exercise, blood volume also increases so there are more red blood cells to carry oxygen.

All of this has the effect of decreasing an athlete's resting heart rate because the heart doesn't have to work as hard. The cardiorespiratory system is more efficient at delivering oxygen to cells.

Regular aerobic exercise can also raise HDL levels, which can decrease risk of heart disease. This has no impact on resting heart rate.

IV Benefits of regular ANAEROBIC (without oxygen) activity

ANAEROBIC activity is defined as all-out exertion lasting less than about 60 seconds. Examples include sprinting and lifting heavy weights.

Anaerobic activity increases muscle strength. Activities like lifting weights can increase muscle endurance if lifting lighter weight with more repetitions, but then the activity would likely be aerobic.

Which of the 4 components of fitness would NOT be achieved if on a regular basis you jogged one day and lifted weights the next? ______________________

Note: The answer to this is suppose to be flexibility, but I recently read a research article which found that strength training did improve flexibility. However, the researchers still concluded that stretching is still an important component to an exercise program.

V Energy Use

What does the purple arrow represent in the image below?

Does it represent glycolysis, or does it represent the Krebs cycle?

Click here if you think it represents glycolysis.

Click here if you think it represents the Krebs cycle.

You can click on the image if you want to see a larger version.

What does the blue to green to yellow spiraled arrow represent?

Click here if you think it represents glycolysis.

Click here if you think it represents the Krebs cycle.

VI Fuel Use during AEROBIC activity

The image below shows that fat and glucose (blood glucose and muscle glycogen) are the primary fuels used during aerobic activities like walking, cycling, and jogging.

You can click on the image if you want to see a larger version.

At the beginning of this bike ride, the rider is using glycogen & fat, but slightly more glycogen.

As time goes on, the rider is using more fat than glycogen.

When does glycogen run out for this bike rider?

One of the advantages of relying on fat for an energy source is that it is abundant, even in lean people. For example, a man who weights 154 lbs who has a body fat level of 10% has approximately 15 lb of body fat, which is equivalent to more than 50,000 Kcal of energy! This is significantly more energy than can be provided by his stored muscle glycogen (800-2,000 kcal)*

* Information taken from Thompson, M & Manore, M & Vaughan L. (2011). The Science of Nutrition.

Two ways you can manipulate what you do to make glycogen last as long as possible is to:

Train so you build up the number of fat-burning enzymes you make. That means you can burn more fat for energy, conserving glycogen for as long as possible. More highly trained individuals also make more and larger mitochondria. The mitochondria is the powerhouse of the cell where aerobic metabolism takes place.
Eat plenty of whole foods with carbohydrate so you have glucose to make glycogen.

VII Fuel Use during ANAEROBIC activity

Activities like sprinting that are high in intensity and short in duration (30 seconds to 3 minutes) need an energy source that can be used quickly to provide ATP. The breakdown of carbohydrates (muscle glycogen as well as blood glucose) provides this quick energy through glycolysis.

Fat is not a fuel that is used during anaerobic activities because fat is relatively slow to breakdown, and it requires oxygen.

During glycolysis, the six-carbon glucose is converted to two molecules of three-carbon pyruvate. This breakdown does not require oxygen and creates ATP for cells to fuel their work. When oxygen is present pyruvate can continue through Aerobic metabolism, or the Krebs cycle. When oxygen is not present (like in the case of sprinting), pyruvate gets converted into lactic acid. Click here to see an animation on the glycolysis process.

Summary of Fuels Used for Activities of Different Intensities and Durations

Activity Intensity	Activity Duration	Preferred Fuel	Oxygen Needed?	Activity Example
Very High	30 sec. – 3 min.	Glucose	No	Sprinting
High	3 min. – 20 min.	Glucose	Yes	Jogging
Low to Moderate	> 20 min.	Fat	Yes	Walking

VIII Protein as Fuel

Proteins (or more specifically amino acids) are not major energy sources during exercise. Depending upon the intensity and durtion of the activity, amino acids may contribute 3% - 6% of the fuel used during activity. (Information taken from Thompson, M & Manore, M & Vaughan L. (2011). The Science of Nutrition).

Protein is not a major fuel source, but is used to build and repair muscles. The protein needs of different athletes are listed in the table below.

The rule of thumb I use is to double the RDA if you are trying to increase muscle mass, which would mean your protein needs would be 1.6 g/kg/day. (Remember the RDA is 0.8g/kg)

So if you look at your diet analysis reports and see that 60g of protein was recommended, you would need 120g of protein if your goal is to increase muscle mass through a strength training program.

The majority of Americans get plenty of protein and don't need to eat special foods to get adequate amounts of protein, as demonstrated in the table below.

RECOMMENDED PROTEIN INTAKES FOR ATHLETES

The above information taken from Nutrition Concepts and Controversies, 2012.

If you are an athlete, the extra protein you need is mainly needed to build and maintain muscle and other lean tissue. If you want to gain 1 pound of muscle per week, you only need 14 grams of extra protein per day, the amount in 2 ounces of meat (Bernardot 1992). Exercise, not extra protein, is the key to developing bigger muscles. Any excess protein that you take in beyond the above recommendations is burned for energy or, stored as glycogen or fat (depending on Calorie intake). Humans do not store excess protein as muscle, protein, or amino acids.

COMMON QUESTIONS REGARDING PROTEIN*

1. What’s the concern of too much protein? You’ll crowd out carbohydrates which fuel your muscles. When athletes focus too much on protein, and not enough on carbohydrates they often sacrifice health and performance. Your body can only use 20 to 25 grams of protein at one time. (There are about 70 grams of protein in an 8 oz. chicken breast)

2. Do I need to eat as soon as I finish exercising? There is a 45 min. post exercise window to nourish, repair, and build muscles. You can switch out of the muscle breakdown mode by eating a combination of carbohydrate and protein as soon as tolerable after you exercise. Good examples of this are a yogurt and fruit, chocolate milk, or a peanut butter sandwich.

3. Do I need to eat protein every 3 to 4 hours to support muscle growth? Yes, when amino acid levels are above normal, the muscles take up more, enhancing muscle growth. Protein containing meals and snacks should be evenly distributed throughout the day.

4. Are protein supplements better than real food? Protein supplements are a mindless way to get protein, and are often quick and convenient, but they don't offer any benefit over whole foods. The advantage of getting protein from whole foods is that protein comes packaged the way nature intended, and whole foods also contain phytochemicals and other yet-unknown bioactive compounds that might influence muscle growth. Whole foods are also typically less expensive than protein supplements.

*The above information was taken from Nancy Clark's Sports Nutrition Guidebook, 2014.

IX Fluids and Temperature

Sweat helps protect you from overheating because it absorbs a lot of heat before it changes from a liquid to a gas (evaporation).

Your lecture outline has a chart comparing
Heat EXHAUSTION and
Heat STROKE

Heat STROKE is more dangerous because the high temperature can denature body proteins, which can lead to loss of brain function and death.

X Sports Drinks

Water is all you need if exercising less than about one hour.

What sports drinks offer besides fluid, to those exercising over one hour:

Electrolytes like sodium- may accelerate glucose & water absorption from digestive tract. About 225 mg per 12 oz. (150 mg per cup) is enough.
Glucose: no more than 7%, which is about 23 grams per 12 oz. (15 grams per 1 cup). More sugar than that delays fluid going from the stomach to the small intestine where it can be absorbed.
Psychological edge
Taste

Homemade sports drink: 1 qt. water, 1 cup sugar-sweetened fruit juice, 1/3 tsp. salt