what is energy? energy is defined as the capacity to do work one of the more common ways to express...
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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
Carbohydrate (CHO) MetabolismCarbohydrate (CHO) Metabolism
• 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
Carbohydrate (CHO) MetabolismCarbohydrate (CHO) Metabolism
• 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
Carbohydrate (CHO) MetabolismCarbohydrate (CHO) Metabolism
• 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
LipidsLipids
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
The Energy ContinuumThe Energy Continuum
• 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 Energy ContinuumThe Energy Continuum
• The O2 system is the dominant system five minutes into exercise
• The longer the exercise, the more important it becomes
The Energy ContinuumThe Energy Continuum
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
gen
Con
sum
ptio
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
Factors That Influence Aerobic Training Factors That Influence Aerobic Training
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
Factors That Influence Aerobic Training Factors That Influence Aerobic Training
1. Initial level of aerobic fitness
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”
Factors That Influence Aerobic Training Factors That Influence Aerobic Training
1. Initial level of aerobic fitness
2. Training intensity• Relationship between %HRmax and %VO2max
%HRmax %VO2max
50 28
60 40
70 58
80 70
90 83
100 100
Factors That Influence Aerobic Training Factors That Influence Aerobic Training
1. Initial level of aerobic fitness
2. Training intensity
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
Factors That Influence Aerobic Training Factors That Influence Aerobic Training
1. Initial level of aerobic fitness
2. Training intensity
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
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• No magic number (depends on exercise intensity)• Duration needs to increase if intensity is lower
• e.g. 60 min at exercise intensities < 70% HRmax
Factors That Influence Aerobic Training Factors That Influence Aerobic Training
• 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
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