Lecture 9 - Ch. 9 PDF

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Ch. 9...

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Lecture 9: Metabolic Rate

O3: (4.686 kcal / LO2) X ( 1 LO2 / 1 min) X (10 min) = (4.686) X (10) = 47 kcals Burning 100% fat and 0% carbohydrates

Respiratory Quotient (RQ) vs. Respiratory Exchange Ration (RER): • How many k/cal per liter oxygen you can get and the fuel mixture in it • Q: If you have an RQ/RER of 0.70 and a VO2 of 1 L/min. How many calories would you burn for a 10 minute exercise? • 4.686k cal/LO2 * 1L/min*10 min= 47 calories for 10 min exercise • Burning 100% fat and 0% carbohydrates • RQ vs. RER • RQ: cellular measurement; in your cells • Oxidizing carb vs fat • RER: usually measuring this, at the mouth • Producing CO2 when oxidizing carbs and fat • Also produce CO2 when doing bicarbonate buffering (breathe CO2 out to maintain blood pH) • Favoring carb oxidation – closer to 1.0 Metabolism ● Metabolism- involves all chemical reactions of biomolecules within the body that encompass synthesis (anabolism) and breakdown (catabolism) ● Three factors affect total daily energy expenditure (TDEE): ○ 1) Resting metabolic rate, consisting of basal and sleeping conditions plus the metabolic cost of arousal ○ 2) Thermogenic effect of food consumed ○ 3) Energy expended during physical activity, recovery, fidgeting ● All the reactions relating to catabolism and anabolism ● Synthesize ATP and proteins, etc Components of Total Daily Energy Expenditure: ● Thermic effect of feeding (10%) ○ Food intake; cold stress; thermogenic drugs) ○ Obligatory thermogenesis ○ Facultative thermogenesis ○ Eating something and have to chew and digest it which expends energy

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Thermic effect of physical activity (15-30%) ○ Duration and intensity -> changes a lot ○ In occupation ○ In home ○ In sport and recreation Resting metabolic rate (60-75%) ○ Fat-free body mass, gender, thyroid hormones, protein turnover -> largely dependent on your body ○ Sleeping metabolism ○ Basal Metabolism ○ Arousal Metabolism

Basal and Resting Metabolic Rates -- interchangeably used but there is a slight difference between the two ● Basal Metabolic Rate (BMR) ○ Minimum level of energy to sustain vital functions in the waking state ○ Reflects the body’s total heat production at the minimum ○ Measured under completely ideal situations in the lab ● Resting Metabolic Rate (RMR) ○ Always slightly higher than BMR ■ Influences: body size, health/fitness/, muscle mass, age, hormones, body temperature ○ Trying to estimate the BMR (plus or minus 10%) ● BMR = sum of metabolic processes requiring to sustain normal regulatory balance and body functions during the resting state ○ Largely dependent upon body size ● Oxygen consumption values for BMR range between 160 and 290 mL/min (0.8 to 1.43 kcal ● BMR in calories per day: dependent on body size ○ Depends on how we got those calories ○ Also express it in VO2 Metabolic Size Concept: ● Surface Area Law (fundamental relationship between heat production and body size) ○ BMR and RMR vary in proportion to the square of body surface area per hour (kcal/m2/h) ○ Females have 5 to 10% lower BMR than males of the same age and size from more fat and less fat-free mass ● The concept of metabolic size relates BMR to body mass raised to the 0.75 power (BM0.75) ● BMR expressed relative to BM0.75 holds true for humans and most mammals and birds that differ considerably in size and shape ● Largest determining factor is your body size

Metabolic Rates of Humans: Age and Gender Comparisons ● Estimates of BMR or RMR fall within ±10% of laboratory values ● Changes in body composition (decrease in FFM and/or increase in %body fat) can explain the 2 to 3% per decade BMR reduction observed ● for adults ● Females exhibit an average 5 to 10% lower BMR than males of same age ○ Due to less fat-free mass and more body fat (fat has lower metabolic activity than muscle) ● Lean tissue has a slightly higher metabolic rate than fat tissue ● Resting metabolic rate increasingly goes down as we age: losing muscle and gaining fat ● Higher metabolic rate – lean tissue has higher metabolic rate than fat tissue Estimating Resting Daily Energy Expenditure (RDEE): ● Usually expressed in kcal/h or kcal/d ○ Can be estimated from BMR (kcal/m2/h) and surface area (m2) ○ Can be estimated from fat-free mass (FFM) ■ RDEE (kcal/d) = 370 + FFM (kg) ● Can be estimated from BMR or FFM ● FFM using body composition assessment and add to constant ● Total energy expenditure: depends levels of activity ○ Can add some factures to equation to get a more likely RDEE BMR as a Function of Age and Gender: ● As you get older, BMR goes down because you start to lose muscle (loose lean tissue) ● Slow this process down by being active Contribution of Diverse Tissues of Human Metabolism: ● Estimates of absolute and relative VO2 uptake of various adult organs and tissues ● Body is going to use different body expenditures in different organs ● When you start exercising, the % going to your muscles is going up and up and up

Organ

Oxygen Consumption (mL ∙ min−1)

% of Resting Metabolism

Liver

67

37

Brain

47

19

Heart

17

7

Kidneys

26

10

Skeletal Muscle

45

18

Remainder

48

19

250

100

5 Factors That Affect TDEE (Total Daily Energy Expenditure) 1. Physical activity a. Have the biggest ability to change/influence on this factor b. We have the most control for physical activity 2. Diet-induced thermogenesis 3. Calorigenic effect of food on exercise metabolism 4. Climate a. if you’re cold, you will maintain your own body temp by secreting hormones and/or shivering OR if it’s hot, and you have an elevated core temperature you will have a higher energy expenditure b. Goal have an ambient temperature so you will not shiver while resting 5. Pregnancy Physical Activity Effects on TDEE ● Physical activity exerts by far the most profound effect on human energy expenditure ○ Accounts for 15 to 30% of TDEE… may be a higher percentage depending on lifestyle (athletes) ● Regular physical activity stimulates resting metabolism ● Regular endurance and resistance exercise offsets the decrease in resting metabolism that usually accompanies aging ● Each 1 lb gain in FFM increases RMR by 7-10 kcal/d ● Sympathetic nervous system increases metabolic rate Diet-Induced Thermogenesis (DIT) or the Thermic Effect of Food (TEF) ● Food consumption increases energy metabolism ○ Obligatory thermogenesis: energy required to digest, absorb, and assimilate food nutrients ○ Facultative thermogenesis: activation of sympathetic nervous system and its stimulating influence on metabolism. Reaches maximum within 1 hour following a meal ● Overweight individuals often have a blunted thermic response (lowered metabolism) that contributes to excess body fat accumulation ○ Less stimulation of the sympathetic nervous system drive and feed forth a mechanism of gaining weight Calorigenic Effect of Food on Exercise Metabolism ● The calorigenic effect of food on exercise metabolism nearly doubles the food’s thermic effect at rest ● DIT of carbohydrate and protein exceeds lipid DIT ● For most individuals, it seems reasonable to encourage moderate physical activity after eating to possibly augment a diet-induced increase in caloric expenditure for weight control

Climate ● Environmental factors influence metabolic rate ○ RMR of people in a tropical climate averages 5-20% higher than those living in temperate areas ○ Have higher body temperatures ○ Temperate environment = at the most risk (ex = san diego) ● Exercising in hot weather causes about a 5% higher in O2 consumption ○ Results from an elevated core temperature, energy for sweat gland activity and altered circulatory dynamics ● Cold environments increase energy metabolism during rest and exercise ○ Depends on body fat content and effectiveness of clothing Classification of Physical Activities by Energy Expenditure 1. Classifying strenuousness of physical tasks: a. Intensity - how hard you perform; can be based on %VO2 max i. higher percentage is harder, carbohydrates burned ii. under 30% and you’ll be burning more fat b. Duration - how long you perform activity 2. Physical activity ratio (PAR) a. Classifies work as the ratio of energy required for a task to the resting energy requirement i. Light work - up to 3x the resting requirement ii. Heavy work - 6-8x resting metabolism (energy expenditure right now in class) 1. Moderate = 150 minutes of exercise a week iii. Maximal work - 9x or more rest 1. Vigorous = above 6 METs, 75 min a week 3. MET, metabolic equivalent: a. Multiples of RMR → resting metabolism i. 1 MET = resting metabolism b. Depends on body weight/size c. One MET equals resting oxygen consumption i. 250 mL/min for men ii. 200 mL/min for women d. Exercise at 2 METs requires twice the resting metabolism, 3 METs equals 3x rest, etc e. To consider variations in body size, express METs in VO2 per unit body mass i. 1 MET equals 3.5 mL/kg/min ii. Allows us to compare small vs larger sized people f. Exercise: values don’t change among different ages → absolute criteria i. Light = 1-3 MET ii. Moderate = 3-6 METs (150 min a week) iii. Vigorous = above 6 MET (75 min a week)

Daily Rates of Average Energy Expenditure ● The average man (19-50y) expends 2900 kcal/d ● The average woman expends 2200 kcal/d ○ Most people spend nearly 75% of their day in light energy expenditure activities ■ 8h lying down/sleeping ■ 6h standing ■ 2h walking/recreational activities ○ Size is the most important difference between the males and female = REE is higher for males ■ REE is higher in males ● Relationship between body mass and oxygen consumption during walking: ○ Larger you are, the greater amount of oxygen consumed Influence of Body Mass ● Increases in body mass raise energy expended in many activities, especially in weightbearing exercise ○ With weight-supported exercise (ex: stationary cycling), the influence body mass on energy cost decreases considerably ● For overweight persons, weight-bearing exercise generates a considerable caloric expenditure ● Expressing energy cost per kg of body mass reduces energy cost differences between individuals regardless of age, race, gender, and body mass Relationship Between Body Mass and Oxygen Consumption During Walking ● As body mass increases, oxygen consumption increases Heart Rate to Estimate Energy Expenditure ● For each individual, heart rate (HR) and VO2 relate linearly over the range of exercise intensities to about 80% of maximum ○ Exercise HR can provide an estimate of VO2 and thus energy expenditure during aerobic exercise ○ Many factors independent of and in addition to exercise limit the use of exercise HR to estimate energy expenditure ■ Environmental temperature, emotions, food intake, body position, musculature, continuous vs. discontinuous mode, static or dynamic movements ● Ex: linear relationship between heart rate and VO2 for 2 female basketball players of different aerobic fitness levels ○ Note differences in slopes of the 2 lines, indicating different fitness levels ■ Not as high of slope line = more fit ■ Higher slope line = less fit ○ Want to be player B = more lean, can exercise harder ■ HR and VO2 are in sync Gross vs. Net Energy Expenditure

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Gross energy expenditure (GEE) includes resting energy expenditure (REE) Net energy expenditure (NEE) is the true energy expenditure of an activity ○ NEE = GEE - REE (for equivalent time) Activities with variation in pace (tennis, soccer, basketball) require frequent measurement for accurate energy expenditure estimates Strenuous exercise with anaerobic involvement limits accuracy in estimating energy expenditure

Economy of Human Movement ● Movement economy: energy required to maintain a constant velocity (steady-rate) of movement ● Requires evaluation of VO2 consumed during exercise at constant power output or velocity ● Only applies to steady-rate exercise where VO2 consumed closely mirrors energy expenditure ● Takes on added importance during longer-duration exercise ○ Improvement in economy reduces VO2 uptake and usually results in improved performance Mechanical Efficiency (ME) ● Relates amount of energy required to perform a task to actual energy requirement of work done ● Reflects percentage of total chemical energy expended that contributes to external work, with remainder lost as heat ● ME (%) = external work accomplished / energy expenditure x 100 ● ME ranges between 20-25% for walking, running, and stationary cycling ● ME declines below 20% for activities with substantial drag forces ● Body size, gender, fitness level, and skill affect individual differences in ME ● Delta efficiency provides an alternative approach to ME calculations ○ Delta efficiency: Change in Work production / Change in energy expenditure x 100...