METABOLIC calculations

METABOLIC calculations - Importance of Metabolic...

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Unformatted text preview: Importance of Metabolic Calculations Metabolic Calculations Calculations Chapter 5 and Appendix D Metabolic Topics Work, Work, Energy, Power as they relate to calorimetry Expressions Expressions of oxygen uptake Concept of the MET Metabolic Metabolic calculations Case Case studies It It is imperative that the exercise physiologist is able to interpret test results and estimate energy expenditure. di Optimizing Optimizing exercise protocols. Exercise Exercise prescription. Weight Weight loss. Work and Energy Work Work - Application of force through distance Work Work = Force x distance (i.e.kg x m) (i. Force Force is constant W = 70 kg x 0.75 meters 52. kg• 52.5 kg•m or 515 Joules Energy Energy – capacity to perform work 1 kcal = 4,186 J CHO CHO = 5.05 kcal • LO2 Fat Fat = 4.74 kcal • LO2 Each L of O2 consumed = 5 kcal 1 Power (on different modes) • Power – Amount of work per unit time • Bike • work/time (I.e. kgm/min; Watt) • 1 W = 6 kgm•min-1 • Note = For cycle ergometry you must account for • kg • distance the flywheel moves the kg with one turn • rev•min-1 • I.e. Monarch = 6 m • rev -1 • Power = (2 kg x 6 m • rev -1 x 60 rev•min-1) = 720 kgm•min-1 or W Power (on different modes) • Power – Amount of work per unit time • Step – • step height (m) • 4 cycle steps / minute (f) • Treadmill • Speed (m/min) • Grade (% grade – use decimal) Energy Expenditure Understanding Understanding energy expenditure is important for weight loss, work tasks, exercise prescription, etc. Calorie Calorie - basic unit of measure of energy expenditure Direct Direct and Indirect Calorimetry can be used to estimate energy expenditure Calorimetry Direct Calorimetry Calorimetry Metabolic Chamber (enclosed) Slide 8 Indirect Calorimetry Calorimetry Closed or Open Circuit Spirometry Indirect Calorimetry, Slide 11, Slide 10 2 Calorimetry Calorimetry Indirect Calorimetry Calorimetry Calorimetry 3 Indirect Calorimetry: Variables Obtained Oxygen Oxygen consumption and carbon dioxide production (VO2, VCO2) Respiratory Respiratory exchange ratio (RER or R)Noninvasive Noninvasive method to estimate the relative contribution of fat and CHO to energy metabolism RQ RQ during steady state conditions VCO VCO2/VO2 Need a link In In research and in practice, we use information obtained from open-circuit spirometry to give openus estimates of energy expenditure, aerobic power and fuel utilization power, and fuel utilization. For For example, we can use oxygen consumption measures to help us determine caloric expenditure during exercise. Calorie/ Calorie/ energy expenditure i.e. i.e. 1 liter of VO2 = ~ 5 kcals For example: How How many calories are you burning if you exercise in a step class using an 8 inch bench? If we need to know the oxygen If we need to know the oxygen consumption consumption (workload) for someone exercising at 6 mph at 5% grade….. If If we need to figure out, how long it will take an individual to loose a certain amount of weight…. 4 Expressions for O2 uptake (VO2) We We will be using metabolic calculations to calculate oxgyen consumption and calories Oxygen Oxygen consumption in humans can be expressed in two different forms expressed in two different forms Absolute (L· Absolute – (L·min-1 or ml·min-1): Can be used in a or ml· form that will yield rate of energy expenditure (1 (1 L of O2 = 5 kcal) (ml•kg (ml•kg-1•min-1): Relative Relative – used to compare individuals of different body size and to better quantify aerobic fitness level MATH AND UNITS ?? Make Make sure that you have your answer is in the right units. Make Make sure your answer units make physiological sense Make Make sure your answer units agree with the problem (i.e. apples = apples NOT apples = oranges) Make Make sure you cancel out units correctly i.e. i.e. 3 L/K X 5 K/ P = 15 L/Ps Expressions for O2 uptake (VO2) Absolute (L· Absolute – (L·min-1 or ml·min-1): Can be or ml· UNITS ! UNITS ! yield rate!of used in a form that will UNITS energy expenditure good for converting energy expenditure ; good for converting oxygen oxygen consumption into calories (1 (1 L of O2 = 5 kcal) Relative (ml•kg Relative – (ml•kg-1•min-1): used to compare individuals of different body size and to better quantify aerobic fitness level Example 5 apple/oranges X 6 orange/ bananas = ??? apple/oranges 30 30 apple / bananas ÷ 6 oranges = ??? 5 apple/ banana/ oranges apple/ Expressions Expressions of units a/ a/ b/ c is the same as a•b-1•c-1 5 MET METs Clinically, Clinically, the MET or “Metabolic equivalent” is used to express energy expenditure and to prescribe prescribe exercise in clinical settings. 1 MET = 3.5 ml•kg-1•min-1 MET ml• For For example 80 80 kg man working at 2.5 L•min-1 2,500 mL•min 80kg 2,500 mL•min-1 / 80kg = 31.25 ml•kg-1•min-1 ml• 31.25 ml• 31.25 ml•kg-1•min-1 / 3.5 = 8.9 METs Met Calc warming up Man Man weighing 200 lbs has pk O2 uptake = 4.0 L•min-1 What What is his relative oxygen consumption? How How many METs is this? A woman weighing 155 lbs has VO2 pk = 32.1 ml•kg-1 • min-1 woman ml• What What is her absolute oxygen uptake? How How many METs is this? What What is the difference between indirect and direct calorimetry? calorimetry? 6 Practice with O2 calculations Man Man weighing 176 lbs has pk O2 uptake = 4.4 L•min-1 What What is his relative oxygen consumption? How How many METs is this? A woman weighing 140 lbs has VO2 pk = 36.7 ml•kg-1 • min-1 140 lb VO 36 What What is her absolute oxygen uptake? How How many METs is this? How How many METs would 70% of her peak capacity be equivalent to? How How many calories per minute is she burning at her peak? How How many calories per minute is she burning at 70%? ACSM Metabolic Calculations Can Can estimate energy expenditure if you have Vertical Vertical component Horizontal Horizontal component Resting Resting component Useful Useful conversions (Memorize) (Memorize) Always Always convert lb to kg (lb/2.2) Centimeters = in x 2.54 Convert Convert speed from mph to m/min (mi/h X 26.8) 1Watt 1Watt = 6 kgm•min-1 kgm•min Remember Remember equivalents Watts Watts to kgm •min-1 kcals kcals (3,500 kcals = 1 lb of fat gain or loss) 1 L O2 = 5 kcals For For weight loss purposes, always account for resting metabolic rate, weekly physical activity and energy expenditure, and food intake Estimation of Energy Expenditure We We can estimate energy expenditure through American American College of Sports MedicineSM Metabolic Equations Special Special considerations for these equations Need to assure that person is at steady state in order to use th equations There There is a variance in prediction Need Need to consider environmental considerations No railNo rail-holding and make sure equipment is calibrated Gross Gross Vs. Net O2 cost Metabolic Calculations – (see also page 216) Walking Walking (S=Speed; G=Grade) VO (0.1• VO2 = (0.1• S) + (1.8 • S • G) + 3.5 Treadmill Treadmill and Outdoor Running VO (0.2• VO2 = (0.2• S) + (0.9 • S • G) + 3.5 Leg Ergometry (watch the units here) th VO VO2 = (10.8 • W • M-1) + 7 OR VO ((kgm VO2 = ((kgm • min-1) • 2) + (3.5 • W) Arm Arm Ergometry VO VO2 = (18 • W • M-1) + 3.5 Stepping Stepping VO (0.2• VO2 = (0.2• F) + (1.33 • 1.8 • H • f) + 3.5 7 Break it down – Walking equation oxygen consumption (ml/kg/min) VO [(0.1• VO2 = [(0.1• S)] + [(1.8 • S • G)] + 3.5 Horizontal component – i.e. oxygen cost of Speed (units are Speed (units are carrying m/min) m/min) body in horizontal body in horizontal direction over distance Vertical component – i.e. (units are ml/kg/m) oxygen cost of carrying body in vertically(units are ml/kg/m) grade Resting oxygen consumption (ml/kg/min) Useful calculation tips to live by Practice Calculation (from pg 311) Write Write down all known’s and do any necessary conversions first. Calculate Calculate each component separately, then complete the calculation complete the calculation A 71-year-old man weighing 180 lb walks on a 71-yearmotormotor-driven treadmill at 3.5 mph and a 15% grade. I.e. I.e. vertical, horizontal, resting Make Make sure your answer agrees with the question in numerical and unit form (always (always What is the oxygen consumption What is the oxygen consumption What What is the MET level How How many calories is he burning at this level? provide units!!!) 8 More Practice Calculations A client weighs 155 lbs was determined to client have a VO2 pk of 45 ml/kg/min. What What is his oxygen consumption in absolute terms? In In METs? How many kcals How many kcals/min is he expending? is he expending A 23-year-old woman weighing 150 lb jogs 23-yearon a motor-driven treadmill at 5.8 mph and motora 0% grade. What What is the oxygen consumption? What What is her MET level? How How many kcals/min is she expending? kcals/min …and Even More Practice Calculations - bonus A cardiac patient has just entered your cardiac cardiac rehabilitation program and has an exercise prescription to exercise 40 minutes at 6 METs, 4 days per week and the client weight 210 lbs. Calculate Calculate the following Treadmill Treadmill grade for a speed of 2.5 mph Step Step rate for a 4 inch bench Resistance Resistance for a monarch bike at 50 rpm Total Total caloric expenditure for each workout session 9 ...
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