Power Power is how much work is accomplished per unit time. The unit for power is watt (W) It is defined as 1 joule per second Power = work ÷ time Power describes the rate at which work is being done  describes the intensity of exercise. 1

Work Work = product of force multiplied by distance: Work = force x distance The SI unit for force is Newtons (N) Lifting a 10kg weight up a distance of 2m the work performed Work = 97.9N x 2m = Joules 1kg = 9.79N so 10kg = 97.9N 2

Measurement of Work and Power Ergonometry = to the measurement of work output. Ergometer = to an apparatus or device used to measure a specific type of work 3

Bench Step The bench = form of ergometer It involves stepping up and down on a bench at a specified rate. E.g 70kg man steps up and down on a 50cm(0.5m) bench for ten minutes at a rate of 30 steps per minute. Work performed: Force = N (i.e., 70kg x 9.79 N/kg) Distance = 0.5m/step x 30 steps/min x 10min =150m Total work performed : N x 150m = Joules or 102.8kilojoules The power output during this exercise can be calculated as: Power = Joules/600seconds = watts 4

Cycle Ergometer =stationary exercise bicycle that permits accurate measurement of the amount of work performed. It incorporates a belt wrapped around the wheel (flywheel). Distance traveled = distance covered per revolution of the pedal (6 meters per revolution on a standard Monarch) This is multiplied by the number of pedal revolutions. 5

Evaluating Immediate Energy System Power = F x D/time Short term muscular power: e.g sprinting up flight of steps Jumping power tests: may not measure anaerobic power = too brief to evaluate ATP & PCr. 6

Evaluating Immediate Energy Systems Other power tests last 6 to 8 seconds. Power tests = high degree of task specificity.  Best sprinter may not be the best repetitive volleyball leaper. 7

Evaluating Short-Term Glycolytic Energy System Glycogen depletion in specific muscles activated = indication of contribution of glycolysis to exercise Tests demanding maximal work for up to 3min = best estimate of glycolytic power. 8

Measuring Anaerobic Capacity No clear method for measuring anaerobic capacity Accepted methods: – Maximal accumulated O 2 deficit – Wingate anaerobic test – Critical power test 9

Wingate test: Peak power output, average power output, anaerobic fatigue What is anaerobic fatigue? = percentage decline in power relative to peak power. 10

Energy Expenditure During Maximal Anaerobic Exercise No activity = 100% aerobic or anaerobic Estimates of anaerobic effort involved – Excess post exercise O 2 consumption (EPOC) – Lactate threshold 11

Anaerobic Energy Expenditure: EPOC O 2 demand > O 2 consumed in early exercise – Body = experiences O 2 deficit – Occurs when anaerobic pathways used for ATP production O 2 consumed > O 2 demand in early recovery – Excess post-exercise O 2 consumption (EPOC) 12

Anaerobic Energy Expenditure: Lactate Threshold Lactate threshold: point at which blood lactate accumulation  Lactate production rate > lactate clearance rate – Good indicator of potential for endurance exercise 13

Anaerobic Energy Expenditure: Lactate Threshold Lactate accumulation  fatigue – Ability to exercise hard without accumulating lactate = beneficial to athletic performance – Higher lactate threshold = higher sustained exercise intensity = better endurance performance For 2 athletes with same V O 2max  higher lactate threshold predicts better performance 14

Measuring & Evaluating the Aerobic System Direct Calorimetry: = Process of measuring metabolic rate via measurement of heat 15

Direct Calorimetry Theory: when body uses energy to do work, heat is given off.  measure heat production (calorimetry) gives a direct measurement of metabolic work. 16

Measuring & Evaluating the Aerobic System Airtight chamber (calorimeter) insulated from environment Exchange O 2 & CO 2 Body temperature raises temperature of water Heat production calculated 17

Measuring & Evaluating the Aerobic System Indirect Calorimetry Theory: Since direct relationship between O 2 consumed & amount of heat produced by body  measurement of O 2 consumption provides estimate of metabolic rate. Measurement of O 2 consumption is indirect, since heat not measured directly. 18

Respiratory Quotient Respiratory quotient (RQ) is ratio of volume of carbon dioxide produced to volume of oxygen consumed.  RQ for Carbohydrate is

Respiratory Exchange Ratio Respiratory Exchange Ratio is ratio of carbon dioxide exhaled to oxygen consumed when CO 2 and O 2 exchange  does not reflect food oxidation. 20

Measuring Maximal Oxygen Consumption Test of Aerobic Power Two general criteria needed: – Test that is independent of muscle strength, speed, body size, skill – Test that consists of graded exercise to point of exhaustion (without muscular fatigue) 21

Measuring Maximal Oxygen Consumption  Criteria for true max VO 2 is leveling off or peaking in oxygen uptake. Other criteria: – Oxygen uptake fails to increase by some value – Maximum lactic acid – Maximum predicted HR – R >

Maximal Oxygen Consumption The highest maximal oxygen uptakes generally recorded for cross-country skiers, runners, swimmers & cyclists. Lance Armstrong VO 2 max = 83.3 ml/kg/min 23

Measuring Maximal Oxygen Consumption Factors that affect Maximal Oxygen Uptake: – Mode – Heredity – State of training – Gender – Body composition – Age 24

Energy Expenditure During Maximal Aerobic Exercise V O 2max : – Point at which O 2 consumption doesn’t  with further  in intensity – Best single measurement of aerobic fitness – Not best predictor of endurance performance –P lateaus after 8 to 12 weeks of training Performance continues to improve More training = compete at higher percentage of VO 2max 25

Energy Expenditure: Energy Cost of Various Activities Varies with type and intensity of activity Calculated from V O 2, expressed in kilocalories/minute Values ignore anaerobic aspects, EPOC Daily expenditures depend on – Activity level (largest influence) – Inherent body factors (age, sex, size, weight, FFM) 26

Energy Expenditure: Successful Endurance Athletes 1. High V O 2max 2. High lactate threshold (as % V O 2max ) 3. High economy of effort 4. High percentage of type I muscle fibers (Slow, oxidative, fatigue resistant) 27