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Chapter 3Lecture Slides

Measures of EnergyWhat is energy?

• Forms of energy– Mechanical– Chemical– Heat– Electrical– Light– Nuclear

• For sport purposes, mechanical, chemical and heat energy are most important.

Figure 3.1

Human energy

• Mechanical energy– Capacity to do metabolic work

• Chemical energy– Storage form of energy

• Heat energy– Product of metabolism

How do we measure work, physical activity, and energy expenditure

• Work and power– Work = force x distance– Power = work/time

• Measurement systems– English – Metric – International (SI)

Energy measurement systems

Work and power measurement

Measurement of work and physical activity

• Ergometer to measure work output– Cycle– Arm

• Devices to measure physical activity– Pedometer– Accelerometer– Intelligent Device for Energy Expenditure and

Activity– Global Positioning Systems

Measurement of energy expenditure

• Measurement of work is not the same as measurement of energy expenditure– Isometric muscle contraction; no work produced

• Calorimetry measures energy expenditure– Direct calorimetry– Indirect calorimetry

Direct calorimetry

Direct calorimetry

Indirect calorimetry

Indirect calorimetry

• Laboratory conditions– Measurement of oxygen uptake and carbon dioxide

production

• Real life conditions– Doubly labeled water technique

• Stable isotopes of hydrogen and oxygen are ingested• Analysis of urine and blood for hydrogen and oxygen to measure

carbon dioxide fluctuation

What is the most commonly usedmeasure of energy?

• In the United States, the Calorie. In most of the world, the joule.

• 1 gram calorie will increase the temperature of 1 gram of water 1 degree Celsius

• 1000 gram calories = 1 kilocalorie• We shall use the kilocalorie, capitalized as Calorie or

as C, as the most common measure of energy in this text.

Calories in food

The Calories in 8 ounces of orange juice providesenough energy for the average male to run a mile.

Human Energy Systems

• Energy systems for muscular activity in the human body are designed to produce energy for work at varying rates.

How is energy stored in the body?

• Adenosinetriphosphate (ATP)• Phosphocreatine (PCr)• Carbohydrate• Fat• Protein

Energy for metabolic activity

• ATP is the immediate source of energy for metabolic activity, including muscle contraction

• PCr can regenerate ATP rapidly• Both ATP and PCr are in very short supply• Carbohydrate, fat and protein can be metabolized to

produce ATP and PCr

Figure 3.6

Major energy stores in the human body

What are the human energy systems?

Predominant energy systems in runners

Anaerobic power (ATP-PCr)60-200 meters (6-20 seconds)

Anaerobic capacity (anaerobic glycolysis; lactic acid)400-800 meters (43-103 seconds)

Aerobic power (aerobic glycolysis) 5,000-10,000 meters (12-26 minutes)

Aerobic capacity (aerobic lipolysis)42.2-100 kilometers (125-360 minutes)

The ATP-PCr energy system

The ATP-PCr energy system

The lactic acid energy system (anaerobic glycolysis)

Glycolysis

The oxygen energy system

• Aerobic glycolysis– Oxidation of glycogen or glucose

• Aerobic lipolysis– Oxidation of fatty acids

• Aerobic proteolysis (limited energy production)– Oxidation of glucogenic or ketogenic amino acids

Figure 3.10

Figure 3.11

Figure 3.12

Conversion of pyruvate to acetyl CoA

Mitochondria oxidation

Energy pathways for fatty acids

Amino acids and the Krebs cycle

What nutrients are necessary for the operation of the human energy systems?

• Water– Hydrolysis

• Vitamins– B vitamins, as coenzymes, are involved in many energy

processes

• Minerals– Minerals, as metalloenzymes, are also involved in energy

processes; iron is part of hemoglobin to transport oxygen

• Dietary supplements– Carnitine, coenzyme Q10 and others marketed to athletes

Human Energy Metabolism during RestWhat is metabolism?

• ENERGY TERMINOLOGY•

• Basal Metabolic Rate (BMR) – Resting; post-absorptive• Maintain basal metabolism

• Only sleeping metabolism is lower

•

• Basal Energy Expenditure (BEE)• BMR extrapolated over 24 hours

•

• Resting Metabolic Rate (RMR)• BMR + small amounts due to prior activity

•

• Resting Energy Expenditure (REE)• RMR extrapolated over 24 hours

•

• Thermic Effect of food (TEF)

• Also known as Dietary Induced Thermogenesis (DIT)• Post-meal elevation in RMR due to digestive processes

•

• Thermic Effect of Exercise (TEE)• Also known as Exercise Metabolic Rate (EMR)

• Increase in metabolic rate associated with exercise

• Metabolic aftereffects of exercise

•• Total Daily Energy Expenditure (TDEE)

• Sum of BEE (REE), TEE, and TDEE

Human Energy Metabolism during RestWhat is metabolism?

• Metabolism represents the sum total of all physical and chemical changes that take place within the body.

• Anabolic metabolism (anabolism)– Constructive processes

• Catabolic metabolism (catabolism)– Disintegration processes

Metabolism

• Total Daily Energy Expenditure (TDEE)– Basal and resting energy expenditure– Thermic effect of food– Thermic effect of exercise

What factors account for the amount of energy expended during rest?

• Basal metabolism– Basal metabolic rate (BMR)

• Energy needed to stay alive when awake• Only sleeping metabolic rate is lower

– Basal energy expenditure (BEE)• Basal metabolism over 24-hour period

• Resting metabolism– Resting metabolic rate (RMR)

• BMR plus small amounts associated with eating, prior activity• About 10 percent higher than BMR

– Resting energy expenditure (REE)• Resting metabolism over 24 hour period

What effect does eating a meal have on the metabolic rate?

• Metabolic rate is elevated after a meal– Specific dynamic action’– Dietary-induced thermogenesis– Thermic effect of food (TEF)

• TEF is expressed as the % of meal energy content– 5-10% for a mixed meal– TEF may be a consideration in some weight-control diets

How can I estimate mydaily resting energy expenditure

• Estimate not as accurate as BMR test• May be useful for weight control programs• Other methods include effects of daily activity• Simple methods to estimate RMR

– 1 Calorie/kilogram body weight per hour– Various formulae

Estimation of RMR

Estimation of RMR

Estimation of RMR

What genetic factors affect my REE?

• Age– Infancy through adulthood

• Gender– Females REE about 10-15% lower

• Natural hormonal activity• Body surface area

– Genetically lean versus stout

How does body composition affect my REE?

• Body composition – Muscle versus fat

• Losing body weight, both fat and muscle, lower REE• Maintaining normal body weight while reducing

body fat and increasing muscle mass may raise REE• Decline in REE with aging may be associated with

loss of muscle mass

What environmental factors may also influence the REE?

• Exposure to cold weather– Thermogenesis

• Exposure to warm or hot weather– Sweating and cardiovascular demands

• Exposure to altitude– Increased ventilation

• Cigarette smoking– Nicotine

• Caffeine– One study found increases of 10 percent

What energy sources are used during rest?

• The oxygen energy system prevails during rest1. About 60 percent of energy from fat– About 40 percent of energy from carbohydrate– Small amount of energy from protein

• The diet may affect the energy source during rest– Eating a diet rich in carbohydrate or fat will,

respectively, increase energy production from carbohydrate and fat

Human Energy Metabolism during Exercise

• Exercise stresses most body systems• Neuromuscular system determines the energy

system to be used during exercise

How do my muscles influence the amount of energy I can produce during exercise

Muscle fiber types

• Three main types of muscle fibers– Type I: Slow twitch red fiber

• Slow oxidative (SO)

– Type IIa: Fast twitch red fiber• Fast oxidative-glycolytic (FOG)

– Type IIb (IIx): Fast twitch white fiber• Fast glycolytic (FG)

Muscle fiber types

What effect does muscular exercise have on the metabolic rate?

• All physical activity increases the metabolic rate• Activities of daily living (ADL)

– NonExercise Activity Thermogenesis (NEAT)

• Planned exercise activity– Exercise metabolic rate (EMR)– Thermic effect of exercise (TEE)

Exercise intensity and metabolic rate

How is exercise intensity measured?

• Actual work output– Ergometer (watts)

• Physiological cost of the activity– ATP-PCr energy system

• Muscle biopsy• Computerized imaging procedures

– Lactic acid energy system• Onset of blood lactic acid (OBLA); steady-state threshold

– Oxygen energy system• Oxygen uptake; maximal oxygen uptake (VO2max)

Figure 3.13

Figure 3.14

How is the energy expenditure of exercise metabolism expressed?

• Calories• Kilojoules• Oxygen uptake• METS

– Multiples of the RMR

Energy expenditure

MET1 MET = 3.5 ml O2/kg body weight/minute

CALORIE (KILOCALORIE)Heat to raise 1 kg of water 11 Calorie = 4.2 kilojoules (kJ)

Energy expenditure

OXYGEN1 MET resting oxygen uptake

3.5 ml O2 x 70 kg = 245 ml O2 per minute

1 Liter Oxygen = c. 5 Calories (kilocalories)

1 Liter Oxygen = 1000 milliliters

245/1000 = 0.245 liter oxygen per minute @ 1 MET0.245 L x 5 Calories/L = 1.225 Calories/minute

Exercise energy equivalencies

How can I tell what my metabolic rate is during exercise?

• Oxygen consumption is precise, but not very practical

• Other physiological measures– Heart rate– Respiratory rate

Figure 3.16

How can I determine the energy cost of exercise?

• Consult appendix B.

What are the best types of activities to increase energy expenditure?

• Activities involving large muscle groups– Walking– Running– Cycling– Aerobic dance– Home exercise equipment– Resistance or strength training (lower than aerobic)

• Intensity and duration

Physical activities to increase energy expenditure

Walking and running

• Walking: – About 1 Calorie/kg body weight/mile or 0.45

Calorie/lb/mile @ 2-4 mph

• Running:– About 1.6 Calories/kg bodyweight/mile or 0.73

Calorie/lb/mile

Cool Website

www.MyPyramid.gov

• Go to MyTracker to calculate the energy cost of your daily physical activities.

Does exercise affect my resting energy expenditure (REE)?

• Metabolic aftereffects of exercise– Excess postexercise oxygen consumption (EPOC)

• RMR remains elevated after intense exercise– % increase in RMR varies, but normally about 4-16%– Time of elevated RMR varies– Total number of Calories is relatively low; < 30

Does exercise affect the thermic effect of food (TEF).

• Research finding are ambiguous• An effect, if any, is believed to be minor

How much energy do I need to consume daily?

• Estimated Energy Expenditure (EER)– Total Daily Energy Expenditure (TDEE)

• Basal energy expenditure (BEE)• Thermic effect of food (TEF)• Thermic effect of exercise (TEE)

Total Daily Energy Expenditure

Estimated Energy Requirement (EER)

• Defined as the dietary energy intake needed to maintain weight in a healthy adult

• A key factor is the Physical Activity Level (PAL), which is the TDEE divided by the BEE. The PAL is used to determine the Physical Activity (PA) coefficient

Estimated Energy RequirementMales (19 years and older)

662 – 9.53 x age + [PA x (15.91 x weight + 539.6 x height)Females (19 years and older)

354 – 6.91 x age + [PA x (9.361 x weight + 726 x height)

Age: In yearsWeight: In kilograms

(Conversion: Multiply pounds by 0.454Height: In meters

(Conversion: Multiple inches by 0.0254)PA: Based on the Physical Activity Level (PAL)

Physical Activity Level (PAL)

Institute of Medicine bases the PAL on the amount of daily physical activity that is the equivalent of walking at a pace of 3-4 MPH, or 15-20 minutes per mile– Low Active (PAL 1.5): Walk 2.2 miles

– Active (PAL 1.75): Walk 7 miles

– Very Active (PAL 2.2): Walk 17 miles

You need not actually walk this amount, but do other physical activities that are the equivalent of walking a mile, such as using an elliptical trainer for 12-15 minutes

Sedentary and very active females22 years old; 132 lbs (60 kg); 55 inches (1.4 m)

Human Energy Systems andFatigue during Exercise

What energy systems are used during exercise?

• Intensity is the most important factor determining which energy system is used during exercise

• Most exercise tasks use a blend of the three major human energy systems, but use of one system will predominate depending on exercise intensity

Predominant energy systems in runnersAnaerobic power (ATP-PCr)

60-200 meters (6-20 seconds)

Anaerobic endurance (anaerobic glycolysis; lactic acid)400-800 meters (43-103 seconds)

Aerobic power (aerobic glycolysis) 5,000-10,000 meters (12-26 minutes)

Aerobic endurance (aerobic lipolysis)42.2-100 kilometers (125-360 minutes)

Major characteristics of the human energy systems

Percentage contribution from aerobic and anaerobic energy sources during different time periods of

maximal work

Aerobic energy system29% of energy in 200-meter dash84% of energy in 1500-meter run

Spencer and Gastin

What energy sources are used during exercise?

• ATP-PCr energy system– Adenosinetriphosphate– Phosphocreatine

• Lactic acid energy system– Muscle glycogen (carbohydrate)

• Oxygen energy system– Muscle glycogen and blood glucose (carbohydrate)– Muscle triglycerides and blood FFA (fat)– Protein (amino acids); minor source of energy

Energy sources during exercise

• Carbohydrate versus fat– Blood glucose and blood FFA during mild exercise; less

than 50% VO2max– Muscle glycogen and muscle triglycerides at higher

intensity

• The crossover concept– Fat is major energy source at low-intensity exercise– Carbohydrate becomes major energy source at higher-

intensity levels• Training increases ability to use both fat and carbohydrate• Elite marathon runners may need 4-5 grams per minute

What is fatigue?

• Fatigue may be chronic or acute

Chronic fatigue

• Overreaching– May impair performance– Planned phase of training

• Overtraining– Prolonged periods of fatigue

• Chronic fatigue syndrome– Genuine medical condition

• Disturbances of immune system• Infections• Mental stress

Acute fatigue

• Acute fatigue may be defined as the inability to continue exercising at a desired level of intensity.

• The site of fatigue– Peripheral– Central

Possible sites of fatigue

What causes fatigue in athletes?

• Peripheral versus central fatigue• The current thinking is that acute fatigue during

exercise is associated with an interaction between peripheral and central factors

• Central factors (brain) make the decision to reduce power output

• Peripheral factors (muscles, blood) may influence the brain

How can I delay the onset of fatigue?

• Proper sport training is the most effective means to delay the onset of fatigue– Physiological training

• Train specific energy systems– Psychological training

• Train for mental strength– Biomechanical training

• Improve biomechanical skills for energy economy

• Nutrition is also important to help delay fatigue

How is nutrition related to fatigue processes?

• Nutritional strategies have been used to help delay or prevent the development of fatigue during exercise using all human energy systems

Examples of some nutritional strategies and, theoretically, how they delay fatigue

Examples of some nutritional strategies and, theoretically, how they delay fatigue

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