what is energy? energy is defined as the capacity to do work one of the more common ways to express...

What is Energy?What is Energy?

• Energy is defined as the capacity to do work

• One of the more common ways to express energy is Calorie

• A calorie is a measure of heat

• There are 1000 calories in a kilocalorie

• A kilocalorie is commonly referred to as a Calorie

What is Energy?What is Energy?

• 1 gram of carbohydrate = 4 C

• 1 gram of fat = 9 C

• 1 gram protein = 4 C

• The calories in food represent a form of potential energy

How is energy stored in the body?How is energy stored in the body?

• Energy is stored in the body in the form of adenosine triphosphate (ATP)

• ATP is a complex molecule that contains a pair of high energy bonds

• When the bond is split by enzymes, energy is quickly released

• This energy is used to fuel body processes (eg. muscle contraction)

ATPATP

• ATP can be regenerated from ADP in three ways:

1. Interaction of ADP with CP

2. Anaerobic metabolism

3. Aerobic metabolism

Creatine PhosphateCreatine Phosphate

• CP is another high-energy compound stored in the muscles

• ADP + CP → C + ATP

• CP donates its P to regenerate ATP

• Process lasts around 10 seconds

Creatine PhosphateCreatine Phosphate

• Recent creatine supp. studies have shown:– increases muscle total creatine (20 g/day for 5

days)– the extent of the increase that is normally

observed is inversely related to the presupplementation level (e.g. vegetarians)

– increased performance in situations where the availability of creatine phosphate is important (high intensity activity with short recovery)

Carbohydrate (CHO) MetabolismCarbohydrate (CHO) Metabolism

• We will continue our discussion of ATP production with CHO metabolism

• Why CHO?– Only food that can create energy anaerobically

– Preferred fuel (requires less O2)

– If you understand CHO metabolism, it’s easy to understand fat and protein metabolism

Carbohydrates (CHO)Carbohydrates (CHO)

• Monosaccharides, disaccharides, polysaccharides

• Most come from plants (exception is lactose found in animal and human milk)

• Most common monosaccharides are glucose and fructose

• Complex CHO are polysaccharides: starch, glycogen, and cellulose


• All CHO must be broken down into glucose before it can continue through the metabolic pathways

• The complete breakdown of glucose is afour-step process


• Imagine the four stages as the four quarters of a football game

• Each step of the is like a single football play

• String the series of plays (steps) together to form an offensive drive (metabolic pathway)

• Two differences– Plays must follow the same order– The final score is predetermined


• First Quarter = Glycolysis

• Second Quarter = Formation of Acetyl CoA

• Third Quarter = Krebs Cycle

• Fourth Quarter = Oxidative Phosphorylation

First Quarter: GlycolysisFirst Quarter: Glycolysis

• Prepares glucose to enter the next stage of metabolism

• Glucose Pyruvate (Lactate)

• ATP is also produced

First Quarter: GlycolysisFirst Quarter: Glycolysis

Glucose

2 Pyruvate

2 ATP 4 ATP

2 NAD+ 2 NADH

Second Quarter: Acetyl CoASecond Quarter: Acetyl CoA

2 Pyruvate

2 Acetic Acid

2 Acetyl coenzyme A

2 CO2

2 NADH

Third Quarter: Krebs CycleThird Quarter: Krebs Cycle

• Krebs cycle begins and ends with the same substance

• No ATP used

• Forms– 2 ATP– 6 NADH– 2 FADH

– 4 CO2

Fourth Quarter: Oxidative PhosphorylationFourth Quarter: Oxidative Phosphorylation

• Series of reactions where ATP is created from the hydrogen atoms that we have accumulated

• Produces 3 ATP for every NADH & 2 ATP for every FADH

The Final ScoreThe Final Score

Quarter Process Product # ATP1st Glycolysis 2 ATP 2 ATP

2nd Pyruvate Acetyl CoA 2 NADH + H+

3rd Krebs Cycle 2 ATP

6 NADH + H+

2 FADH2

2 ATP

4th Oxidative Phosphorylation 2 NADH + H+

8 NADH + H+

2 FADH2

4 ATP *

24 ATP

4 ATP

Final Score 36 ATP

LipidsLipids

• 95% of lipids in our diet are triglycerides

• Triglycerides are divided into:– Saturated fats– Unsaturated fats

• Monounsaturated fats (olive and peanut oils)• Polyunsaturated fats (fish, safflower, sunflower, corn oil)

• The more saturated the product, the harder it is at room temperature

LipidsLipids

• How is percentage of fat in food calculated?– One gram of fat= 9 Calories– Multiply number of grams of fat by 9 and represent

the number of Calories as a percentage of the total Calories per serving.

– e.g. • Calories per serving = 120 Calories• Total fat = 7 grams• 7 x 9 = 63 Calories → 63 / 120 = 52.5% fat

LipidsLipids

Lipids: An Important Energy SourceLipids: An Important Energy Source

• Lipids as an energy source– The part of the lipid molecule that is used for

energy production is the free fatty acid (FFA)– FFA are metabolized by a process called beta-

oxidation– Acetyl-CoA is formed from beta-oxidation

Lipids: An Important Energy SourceLipids: An Important Energy Source

• Lipids as an energy source– Most of the acetyl-CoA enters the mitochondria

and the Krebs cycle– During rest, nearly 60% of the energy supply is

provided by the metabolism of fats

ProteinProtein

• Chains of amino acids

• 20 different amino acids– Essential amino acids (9)– Non-essential amino acids

• Used to synthesize protein in the body

• Also used as a source of energy

• Excess amino acids stored as glycogen or fat

Cellular RespirationCellular Respiration

• Cellular respiration can be either anaerobic or aerobic

• Not an “either/or” situation – both systems work concurrently

• When we describe muscular exercise, aerobic and anaerobic refer to which system predominates

The Energy ContinuumThe Energy Continuum

• ATP-PC systempredominates in activitieslasting 10 seconds or less

• Continues to provide at least 8% for maximal activities up to 2 minutes


• Anaerobic metabolism (ATP-PC & LA) predominates in supplying energy for exercises lasting less than 2 minutes

• Continues to provideup to 15% energyrequirements forexercise as longas 10 minutes


• The O2 system is the dominant system five minutes into exercise

• The longer the exercise, the more important it becomes


0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.167 0.5 1 2 4 5 10 30 60 120

Time of Event (min)

% c

on

trib

uti

on

an

aero

bic

Aerobic O2

Anaerobic LA

ATP-PC

Lactic Acid / Lactate ProductionLactic Acid / Lactate Production

• Lactic acid is produced in muscle cells

• NADH + H+ transfers its hydrogen to pyruvate which forms lactic acid

• The amount of lactic acid present depends on the balance between its production and its removal

Lactic Acid / Lactate ProductionLactic Acid / Lactate Production

• What conditions lead to lactic acid production?– Muscle contraction results in lactic acid production– Fast twitch fibers produce lactic acid when they

contract– Insufficient amounts of oxygen

Why is Lactic Acid a Problem?Why is Lactic Acid a Problem?

• It is the H+ that comes from the lactic acid that is the problem

• Normally we can buffer the H+ to maintain pH

• When the amount of H+ exceeds the capacity to buffer, the pH becomes acidic

• At this point, pain is perceived and performance suffers

Why is Lactic Acid a Problem?Why is Lactic Acid a Problem?

• Pain sources:– Activities that rely on the ATP-PC and LA systems– H+ ions accumulate and stimulate pain nerve

endings located in the muscle

• Performance– Metabolic fatigue– Muscular fatigue

Lactate RemovalLactate Removal

• Lactate is removed from the bloodstream relatively quickly following exercise

• There are wide interindividual differences, but generally half of the lactate is removed in about 15 - 25 minutes (half-life)

• Near-resting levels can be achieved in 30 - 60 minutes

Lactate RemovalLactate Removal

• Evidence suggests that lactate removal occurs more quickly when individual exercises during recovery

• Intensity of the exercise peaks at about 40% VO2max

• Careful! Active recovery can deplete glycogen stores and delay glycogen resynthesis

Lactate Threshold (LT)Lactate Threshold (LT)

• The LT represents an exercise level where the production of lactic acid exceeds its removal

• Function of LT– Indicator of aerobic training status– Predicts endurance performance– Establishes effective training intensity

Aerobic MetabolismAerobic Metabolism

• The aerobic system provides long-term energy

• Occurs in mitochondria

• Includes Krebs cycle and oxidative phosphorylation (3rd & 4th quarters)

Aerobic MetabolismAerobic Metabolism

Exercise time (min)

Oxy

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Con

sum

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n m

l/kg/

min Steady State

Rest

Steady StateSteady State

• Lactic acid does not accumulate in the blood under steady state conditions

• Steady state is different for different people

• Depends on – The capacity to deliver oxygen to the muscles– The ability of the muscles to use the oxygen

Training the Anaerobic System Training the Anaerobic System

• Anaerobic training (sprint/power training)– Increases in resting levels of ATP, CP, creatine &

glycogen and increases in strength– Increases in the quantity of enzymes that control

glycolysis– Increased capacity to generate high levels of

blood lactate

Training the Aerobic System Training the Aerobic System

• Aerobic training – Larger, more numerous mitochondria in muscle– Enhanced breakdown of fat (conserves glyocgen)– Enhanced ability to breakdown CHO during max

exercise– Delay the onset of blood lactate during exercise of

progressively increasing intensity– Body composition changes

Training the Aerobic System Training the Aerobic System

• Aerobic training – Performance changes– Psychologic benefits

Factors That Influence Aerobic Training Factors That Influence Aerobic Training

1. Initial level of aerobic fitness

2. Training intensity

3. Training frequency

4. Training duration


1. Initial level of aerobic fitness• Great improvements can be made if aerobic

fitness is low to start• Aerobic fitness improvements generally range

between 5 & 20% with endurance training



2. Training intensity• Adaptations depend on the intensity of the

overload• %HR is commonly used to set intensity• Aerobic capacity will improve if intensity regularly

maintains heart rate between 55 and 70% of max• “Conversational pace”



2. Training intensity• Relationship between %HRmax and %VO2max

%HRmax %VO2max

50 28

60 40

70 58

80 70

90 83

100 100




3. Training frequency• Number of days/week varies• Some studies report that frequency influences

cardiovascular improvement• Others report that intensity and duration is more

important and frequency is less important




3. Training frequency• Increased frequency is important when weight

loss is desired• To effect meaningful weight loss, exercise session

should be at least 60 min. at an intensity to expend 300 kCal or more




3. Training frequency

4. Training duration• No magic number (depends on exercise intensity)• Duration needs to increase if intensity is lower

• e.g. 60 min at exercise intensities < 70% HRmax


• ACSM Recommendations– Cardiovascular function

• Exercise has an additive effect (3 x 10 min nearly equals 1 x 30 min)

• Intensity = 40-50 to 85% VO2max (55-65 to 90% HRmax)

• Duration = at least 20 to 60 minutes• Frequency = more than 2 days weekly

what is energy? energy is defined as the capacity to do work one of the more common ways to express...

Documents

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calorie slide

protein metabolism slide

aerobic metabolism slide

predetermined slide

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cellulose slide

form of potential energy