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Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8 Energy Expenditure During Rest and Physical Activity.

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Presentation on theme: "Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8 Energy Expenditure During Rest and Physical Activity."— Presentation transcript:

1 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8 Energy Expenditure During Rest and Physical Activity

2 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins ObjectivesObjectives Define the basal metabolic rate, and indicate factors that affect it. Explain the effect of body weight on the energy cost of different forms of physical activity. Identify the factors that contribute to the total daily energy expenditure. Outline the different classification systems for rating the strenuousness of physical activity. Describe two means to predict resting daily energy expenditure. Explain the concepts of exercise efficiency and exercise economy. List factors that affect the energy cost of walking and running. Identify the factors that contribute to the lower exercise economy of swimming compared with running.

3 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Total Daily Energy Expenditure Determined by: –Resting metabolic rate –Thermogenic influence of consumed food –Energy expended during physical activity and recovery

4 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Total Daily Energy Expenditure (Cont.)

5 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Basal (Resting) Metabolic Rate For each individual, a minimum energy requirement sustains the body’s functions in the waking state. Body surface area frequently provides a common denominator for expressing basal metabolism. BMR averages 5% to 10% lower in females compared with males at all ages.

6 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Basal (Resting) Metabolic Rate (Cont.)

7 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Estimating Resting Daily Energy Expenditure Metabolic rate/hour = BMR x surface area (BSA)

8 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Predicting Resting Energy Expenditure Women: RDEE = (9.6 x BM) + (1.85 x S) - (4.7 x A) Men: RDEE = (13.7 x BM) + (5.0 x S) - (6.8 x A)

9 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Factors Affecting Total Daily Energy Expenditure (TDEE) Physical Activity: Accounts for 15%-30% of TDEE Dietary-Induced Thermogenesis: 10%-35% of the ingested food energy Climate: (1) Elevated core temperature, (2) Additional energy required for sweat-gland activity, (3) Altered circulatory dynamics Pregnancy

10 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Factors Affecting Total Daily Energy Expenditure (TDEE) (Cont.)

11 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Energy Expenditure During Physical Activity Body size plays an important contributing role in exercise energy requirements –Heavier people expend more energy to perform the same activity than people who weigh less. Energy expenditure can therefore be predicted during weight-bearing exericse from body mass with almost as much accuracy as measuring oxygen uptake under controlled laboratory conditions.

12 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins METMET Metabolic EquivalenT Provides a convenient way to rate exercise intensity from a resting baseline One MET is an adult’s average, seated resting oxygen consumption or energy expenditure. –3.5 mL O 2 ·kg -1 ·min -1 –1.0 kCal·kg -1 ·h -1

13 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins MET (Cont.)

14 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Efficiency of Energy Use Mechanical Efficiency: % of total chemical energy expended that contributes to external work output –Most affected by energy needed to overcome friction Gross Mechanical Efficiency: The total oxygen uptake during the exercise Net Mechanical Efficiency: Resting energy expenditure subtracted from total energy expended during exercise Delta Efficiency: Ratio of the difference between work output at two levels of work output to the difference in energy expenditure determined for the two levels of work output

15 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Factors Influencing Exercise Efficiency Work rate: As work rate increases, efficiency decreases. Movement speed: Any deviation from the optimal movement speed decreases efficiency. Extrinsic factors: Improvements in equipment design have increased efficiency in many physical activities. Muscle fiber composition: Work done by slow-twitch muscle fibers is more efficient than the same work done by fast-twitch fibers. Fitness level: More fit individuals perform a given task at a higher efficiency. Body composition: Fatter individuals perform a given exercise task at a lower efficiency. Technique: Improved technique produces fewer extraneous body movements, resulting in a lower energy expenditure, and hence higher efficiency.

16 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Economy of Movement The quantity of energy to perform a particular task relative to performance quality Can be assessed by measuring the steady-rate oxygen uptake during a specific exercise at a set power output or speed –At a given submaximum speed of running, cycling, or swimming, an individual with greater movement economy consumes less oxygen All else being equal, a training adjustment that improves economy of effort directly translates to improved exercise performance

17 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Walking Economy A curvilinear relationship exists between energy expenditure versus walking at slow and fast speeds. –A linear relationship exists between walking speeds of km·h -1 (1.9 to 3.1 mph) and oxygen uptake. –At faster speeds, walking becomes less economical so the relationship curves upward to indicate a disproportionate increase in energy cost related to walking speed. –The crossover velocity is ~6.5 km·h -1 (4.0 mph) at which running becomes more economical than walking.

18 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Walking Economy (Cont.)

19 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Walking Economy (Cont.)

20 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Walking Surface and Footwear Effects Walking Surface –Similar economies exist for level walking on a grass track or paved surface. –Energy cost almost doubles walking in sand, and is 3-fold when walking on soft snow. Footwear –More energy is needed to carry added weight on the feet or ankles than to carry similar weight attached to the torso. –Ankle weights increase the energy cost of walking to values usually observed for running.

21 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Energy Expenditure During Running Independent of fitness, it becomes more economical from an energy standpoint to discontinue walking and begin to jog or run at speeds greater than ~6.5 km·h -1 (4.0 mph). The same total caloric cost results when running a given distance at a steady-rate oxygen uptake at a fast or slow pace. For horizontal running, net energy cost per kilogram of body mass per kilometer traveled averages approximately 1 kCal or 1 kCal·kg -1 · km -1.

22 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Running Speed Running speed can increase in three ways: –Increase the number of steps each minute (stride frequency) –Increase the distance between steps (stride length) –Increase stride length and stride frequency

23 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Running Speed (Cont.)

24 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Air Resistance Effects Factors that influence how air resistance affects energy cost of running: –Air density –Runner’s projected surface area –Square of headwind velocity Drafting: Following directly behind a competitor to counter the negative effects of air resistance and headwind on energy cost

25 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Energy Expenditure During Swimming Swimmers’ energy expenditure differs from walking and running in the following ways: –Energy to maintain buoyancy while generating horizontal movement at the same time using the arms and legs, either in combination or separately –Energy needed to overcome drag forces that impede the movement of an object through a water medium These factors all contribute to a considerably lower economy swimming compared with running. –Requires 4x more energy to swim a given distance than to run the same distance

26 Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Energy Cost and Drag Three components comprise the total drag force that impedes a swimmer’s forward movement: –Wave drag –Skin friction drag –Viscous pressure drag


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