Copyright © 2015 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8 Energy Expenditure During Rest and Physical Activity

Copyright © 2016 Wolters Kluwer All Rights Reserved Chapter Objectives Define basal metabolic rate and indicate three factors that affect it. Explain the effect of body weight on the energy cost of different forms of physical activity. Identify three factors that contribute to the total daily energy expenditure. Outline two different classification systems to rate physical activity intensity. Describe two ways to predict resting daily energy expenditure. Explain concepts of exercise efficiency and exercise economy. List three factors affecting energy cost of walking and running. Identify three factors that contribute to lower exercise economy of swimming compared with running. 2

Copyright © 2016 Wolters Kluwer All Rights Reserved Energy Expenditure During Rest Resting energy expenditure determined by: 1.Resting metabolic rate 2.Thermogenic influence of food consumed 3.Energy expended during PA and recovery 3

Copyright © 2016 Wolters Kluwer All Rights Reserved Basal (Resting) Metabolic Rate (BMR) Represents minimum energy requirement to sustain functions in the waking state –BSA provides a common denominator for expressing BMR BMR = kcal m -2 h -1 –BMR averages 5% to 10% lower in females at all ages –Three standardized conditions: 1.No food consumed for a minimum of 12 h before measurement (postabsorptive state) 2.No undue muscular exertion for at least 12 h before 3.Measured after person has been lying quietly for 30 to 60 min in a dimly lit, temperature-controlled, thermoneutral room 4

Copyright © 2016 Wolters Kluwer All Rights Reserved BMR as a Function of Age and Gender 5

Copyright © 2016 Wolters Kluwer All Rights Reserved Estimating Resting Daily Energy Expenditure Metabolic rateh -1 = BMR x surface area (BSA) –BSA,m 2 = X Stature X Body mass –Women: RDEE = (9.6 X BM) + (1.85 X Stature) – (4.7 X Age) –Men: RDEE = (13.7 X BM) + (5.0 X Stature) – (6.8 X Age) 6

Copyright © 2016 Wolters Kluwer All Rights Reserved Contribution of Diverse Tissues to RMR 7

Copyright © 2016 Wolters Kluwer All Rights Reserved Three Factors Affect Total Daily Energy Expenditure (TDEE) 1.Physical Activity –Accounts for 15% to 30% of TDEE 2.Dietary-Induced Thermogenesis (DIT or TEF) –10% to 35% of ingested food energy 3.Climate: Three factors produce increased environmentally induced thermogenic effect 1.Elevated core temperature 2.Additional energy required for sweat gland activity, 3.Altered circulatory dynamic Pregnancy 8

Copyright © 2016 Wolters Kluwer All Rights Reserved Energy Expenditure During PA Body size plays an important contributing role in PA energy requirements –Heavier people expend more energy to perform the same activity than people who weigh less Energy expenditure can be predicted during weight-bearing PA from body mass with almost as much accuracy as lab measured VO 2 9

Copyright © 2016 Wolters Kluwer All Rights Reserved Classification of PA by Energy Expenditure Two factors affect how researchers rate task difficulty –Duration of effort –Intensity of effort 10

Copyright © 2016 Wolters Kluwer All Rights Reserved Rating “Strenuousness of PA PA ratio (PAR) –Ratio of energy required to resting energy requirement Metabolic equivalent (MET) –250 mL O 2 · min -1 –3.5 mL O 2 ·kg -1 ·min -1 –1.0 kcal·kg -1 ·h -1 HR during activity 11

Copyright © 2016 Wolters Kluwer All Rights Reserved Heart Rate to Estimate Energy Expenditure HR and VO 2 relate linearly throughout broad range of aerobic PA intensities – HR during PA provides VO 2 estimate and thus energy expenditure during diverse activities 12

Copyright © 2016 Wolters Kluwer All Rights Reserved Body Size Contributes to Energy Expenditure Relationship between body mass and VO 2 during submaximal treadmill walking 13

Copyright © 2016 Wolters Kluwer All Rights Reserved Five-Level Classification of PA Intensity 14

Copyright © 2016 Wolters Kluwer All Rights Reserved Energy Expenditure of Recreational and Sport Activities 15

Copyright © 2016 Wolters Kluwer All Rights Reserved Average Rates of Daily Energy Expenditure 16

Copyright © 2016 Wolters Kluwer All Rights Reserved Energy Expenditure During Walking, Running, Swimming Efficiency and economy of human movement –Three factors determine success in aerobic performance: 1.Aerobic capacity (VO 2max ) 2.Sustained effort at large percentage of VO 2max 3.Efficiency of energy use (movement economy) 17

Copyright © 2016 Wolters Kluwer All Rights Reserved Efficiency of Human Movement Mechanical Efficiency (ME): % total chemical energy expended that contributes to external work output Gross ME (%) = Work Output ÷ Energy Expended X 100 Net ME (%) = Work Output ÷ Energy Expended Above Rest X 100 –Most affected by energy to overcome friction 1.Gross Mechanical Efficiency: Total VO 2 during PA 2.Net Mechanical Efficiency: Resting energy expenditure subtracted from total PA energy expenditure 3.Delta Efficiency: Ratio of difference between work output at 2 levels of work to difference in energy expenditure determined for the 2 levels of work 18

Copyright © 2016 Wolters Kluwer All Rights Reserved Factors Influencing PA Efficiency Work rate: As work rate increases, efficiency decreases Movement speed: Any deviation from optimal movement speed decreases efficiency Extrinsic factors: Improvements in equipment design have increased efficiency in many PA Muscle fiber composition: Work done by slow-twitch muscle fibers more efficient than same work done by fast-twitch fibers Fitness level: More fit individuals perform given task at a higher efficiency Body composition: Fatter individuals perform a given task at lower efficiency Technique: Improved technique produces fewer extraneous body movements, resulting in a lower energy expenditure and hence higher efficiency 19

Copyright © 2016 Wolters Kluwer All Rights Reserved Movement Economy Quantity of energy to perform a particular task relative to performance quality –Assessed by measuring steady-rate VO 2 during specific activity at set power output or speed –At a set submax speed of running, cycling, or swimming, individual with greater movement economy consumes less oxygen All else being equal, a training adjustment that improves economy of effort directly translates to improved performance 20

Copyright © 2016 Wolters Kluwer All Rights Reserved Economy of Movement Relationship between submax VO 2 running at 268 m/min and 10-km rate time in elite male runners with same aerobic capacity 21

Copyright © 2016 Wolters Kluwer All Rights Reserved Energy Expenditure and Economy of Walking Relationship between walking speed and VO 2 remains linear between km h −1 (1.9 to 3.1 mph) As walking economy decreases at faster speeds, relationship curves upward with disproportionate increase in energy expenditure with increasing speed Per unit distance traveled, faster but less-efficient walking speeds require more total kcal per unit distance traveled 22

Copyright © 2016 Wolters Kluwer All Rights Reserved Prediction of Energy Expenditure (kcal min −1 ) From Speed of Level Walking and Body Mass 23

Copyright © 2016 Wolters Kluwer All Rights Reserved Different Terrain Effects on Walking EE between 5.2 and 5.6 km h -1 24

Copyright © 2016 Wolters Kluwer All Rights Reserved Walking Surface and Footwear Effects Walking Surface –Similar economies exist for level walking on grass track or paved surface –Energy cost almost doubles walking in sand, and 3-fold when walking on soft snow Footwear –More energy required to carry added weight on feet or ankles than to carry similar weight on torso –Ankle weights increase energy cost of walking to values observed for running 25

Copyright © 2016 Wolters Kluwer All Rights Reserved Energy Expenditure During Running More economical to discontinue walking and begin to jog or run at speeds greater than ~6.5 km·h -1 (4.0 mph); effect independent of fitness Same total caloric cost when running a given distance at steady-rate VO 2 at fast or slow pace For horizontal running, net energy cost per kg of body mass per km traveled averages approximately 1 kcal or 1 kcal kg -1 km -1 26

Copyright © 2016 Wolters Kluwer All Rights Reserved Running Speed Running speed can increase in three ways: 1.Increase number of steps each minute (stride frequency) 2.Increase distance between steps (stride length) 3.Increase stride length and stride frequency Well-trained runners run at a stride length “selected” through years of training The body naturally attempts to achieve a level of “minimum effort ” –No “best” style exists to characterize elite runners 27

Copyright © 2016 Wolters Kluwer All Rights Reserved Air Resistance Effects Three factors influence how air resistance affects energy cost of running: 1.Air density 2.Runners projected surface area 3.Square of headwind velocity Drafting: Following directly behind a competitor to counter the negative effects of air resistance and headwind on energy cost 28

Copyright © 2016 Wolters Kluwer All Rights Reserved Energy Expenditure During Swimming Swimming energy expenditure differs from walking and running in two ways: 1.Energy to maintain buoyancy while generating horizontal movement at the same time using the arms and legs, either in combination or separately 2.Energy needed to overcome drag forces impeding object’s movement through water medium These factors contribute to a lower swimming economy compared with running –Requires 4x more energy to swim a given distance than run the same distance 29

Copyright © 2016 Wolters Kluwer All Rights Reserved Energy Cost and Drag Three components comprise total drag force that impedes a swimmer’s forward movement: 1.Wave drag 2.Skin friction drag 3.Viscous pressure drag 30

Copyright © 2016 Wolters Kluwer All Rights Reserved Energy Cost, Swimming Velocity, Skill VO 2 measurements for two elite and two trained swimmers during three competitive strokes –Elite swimmers swim a given speed with lower VO 2 than untrained, skilled swimmers –Breaststroke “costs” most at any speed and represents least economical of the different strokes followed by backstroke –Front crawl least “expensive” and most economical mode among three strokes 31

Copyright © 2016 Wolters Kluwer All Rights Reserved Summary: Part 1 1.BMR reflects minimum energy required for vital functions in the waking state. 2.BMR relates inversely to age and gender, averaging 5% to 10% lower in women than men. 3.FFM and percentage body fat largely account for age and gender differences in BMR. 4.TDEE: sum of energy required in resting metabolism, thermic effect of food, energy generated in PA. 5.Accurate estimate of RDEE: body mass, stature, age, FFM. 6.Five factors significantly impacts TDEE: PA, dietary-induced thermogenesis, environmental factors, pregnancy. 7.DIT: increase in energy metabolism attributable to digestion, absorption, assimilation of food nutrients. 8.Hot and cold environments increases TDEE up to 5%

Copyright © 2016 Wolters Kluwer All Rights Reserved 1.Mechanical efficiency: percentage of total energy expended contributing to external work, with the remainder lost as heat. 2.Exercise economy: energy input versus energy output evaluated by oxygen uptake while exercising at preset power output or speed. 3.Walking speed relates linearly to oxygen uptake between 1.9 and 3.1 mph; walking becomes less economical at speeds faster than 4.0 mph. 4.Walking surface impacts energy expenditure—walking on soft sand requires about twice the energy expenditure as walking on hard surfaces. 5.Heavier people have a proportionally larger energy cost of weight-bearing PA. Summary: Part 2 33

Copyright © 2016 Wolters Kluwer All Rights Reserved 6.Handheld and ankle weights increase the energy cost of walking to values reported for running. 7.More economical to begin jog-run than to walk at speeds between 6.5 km.h −1 (4.0 mph) and 8.0 km.h −1 (5.0 mph). 8.Total energy cost for running a given distance remains independent of running speed. For horizontal running, net energy expenditure averages about 1 kcal.kg −1.km −1. 9.Shortening running stride and increasing stride frequency to maintain a constant running speed requires less energy than lengthening stride and reducing stride frequency. 10.Overcoming air resistance accounts for 3% to 9% of total energy cost of running in calm weather. 11.Running directly behind a competitor (“drafting”) counters negative effect of air resistance and headwind on energy cost. Summary: Part 2 (cont.) 34

Copyright © 2016 Wolters Kluwer All Rights Reserved 12.Same amount of energy to run a given distance or speed on a treadmill as on a track under identical climatic conditions. 13.Children run at a preset speed with less economy than adults; they require between 20% and 30% more oxygen per unit of body mass. 14.Swimming requires approximately four times more energy than running the same distance due to greater energy expended to maintain buoyancy and overcome drag forces. 15.Elite swimmers expend fewer calories to swim a given stroke at any velocity. 16.Three significant gender differences in swimming: body drag, economy, net oxygen uptake. 17.Women expend approximately 30% less energy to swim a given distance compared to men. Summary: Part 2 (cont.) 35