1904 EXPH: Chapter 5 Energy Expenditure

metabolic rate

is the rate of energy use by the body

basal metabolic rate (BMR)

rate of energy expenditure at rest

• in supine position

• thermoneutral environment

• after 8hr sleep

measuring energy expenditure: direct calorimetry

heat production increase with energy production

• can be measured in a calorimeter

• water flow through walls

• body temperature increases water temperature

measuring energy expenditure: direct calorimetry Pro/Con

Pro: good for RESTING metabolic measurements

Con: expensive, heat added by exercise equipment, measurement errors created by sweat, neither practical not accurate for EXERCISE

measuring energy expenditure: direct calorimetry

estimates total body energy expenditure based on O2 used and CO2 produced

• measures respiratory gas concentrations

measuring energy expenditure: indirect calorimetry Pro/Con

Pro: accurate

Con: not comfortable, expensive, time consuming, required trained personnel, participant risk due to maximal exertion

POP QUIZ- what is VO2max

the highest rate of O2 consumption attainable during maximal or exhaustive exercise

• fitness can be measured by the vol of O2 consumed while exercising

• DONE AT YOUR MAX CAPACITY

measuring energy expenditure: O2 and CO2 measurements

• VO2: vol of O2 consumed per minute

  • Rate of O2 consumption

  • Vol of Inspired O2 - Vol of expired O2

• VCO2: vol of CO2 produced per minute

  • Rate of CO2 production

  • Vol of expired CO2 - Vol of inspired CO2

measuring energy expenditure: respiratory exchange ratio

• O2 usage during metabolism depends on the type of fuel being oxidized

  • more carbon atoms in molecule = more O2 needed

  • Glucose (C6H12O6) < Palmitic Acid (sat fatty acid) (C16H32O2)

• Respiratory exchange ratio

  • ratio between rates of CO2 production and O2 consumption

  • RER=VCO2/VO2

POP QUIZ: What fuel are you mainly using at your VO2max?

use RER as the variable to tell you

RER <1

• fat metabolism

• aerobic threshold

• low intensity

RER= 0.85

• fat and glucose metabolism

• aerobic-anaerobic transition

• moderate intensity

RER>1

• glucose metabolism

• anaerobic threshold

• high intensity

exercise intensity and fuel selection

• Low intensity exercise (<30% VO2 max)

  • Fats are primary fuel during prolonged low intensity exercise

• High intensity exercise (>70% VO2 max)

  • CarboH (glucose) are primary fuel

“Crossover concept”

describes the shifts from Fat to CHO metabolism as exercise intensity increases

RER for fat (C6H32O2+ 23 O2→16 CO2 + 16 H2O

RER= VCO2/VO2 = 16 CO2 / 23 O2 = 0.70

RER for CarboH (glucose) (C6H12O6 + 6 O2→ 6 CO2 + 6 H2O)

RER= VCO2/VO2 = 6CO2/6O2 = 1.00

energy expenditure during aerobic exercise

point at which O2 consumption doesn’t increase with further increase intensity

• the primary criterion is a plateau in VO2

best single measurements of cardiorespiratory fitness

• more training allows athlete to compete at higher percentage of VO2max

oxygen consumption: O2 deficit

O2 demand > O2 consumption in early exercise

• delay in oxygen uptake at the beginning of exercise

thus, body incurs O2 deficit

• occurs when anaerobic pathways are used for ATP

(@ ANAEROBIC PATHWAY) → not enough Oxy at early exercise!

oxygen consumption: steady state O2 consumption

a state where oxygen consumption has reached a level that MATCHES the oxygen demand of the exercise

• occurs when aerobic pathway is used for ATP production

oxygen consumption: excess postexercise O2 consumption (EPOC)

• O2 consumed > O2 demand in early recovery

• replenishes ATP/PCr stores, coverts lactate to glycogen, replenishes hemo/myoglobin, clears CO2

• REPAYMENT FOR O2 deficit

EPOC notes

excess postexercise O2 consumption

• EPOC →all oxy that not provided at early exercise will provide at the end of exercise

• (replenish everything) → “repayment for O2 deficit

• if larger oxy deficit = larger EPOC

• if smaller oxy deficit = smaller EPOC

true or false: smaller EPOC in athlete

true, athlete more efficient transmit quick to aerobic and spend less time in APCr and glycolic = smaller oxy = smaller EPOC

true or false: smaller O2 deficit in athlete

true, athlete have smaller O2 deficit bc they transition to aerobic faster due to more capillaries and mitochondria

oxygen consumption: LESS LACTATE PRODUCATION AT THE BEGINNING OF EXERCISE

• less lactate at early exercise

• better developed aerobic bioenergetic capacity due to:

  • cardiovascular adaption (more capillaries)

  • muscular adaptions (greater mitochondria vol)

energy expenditure during maximal aerobic exercise

• absolute VO2 max expressed in L/min

• relative VO2 max normalized for body weight

  • ml O2 * kg -1 * min^-1 (mili per kg per min)

  • more accurate comparison for different body size/ BW

oxygen uptake: trained vs untrained

untrained: reach VO2 max faster

train: reach VO2 slower due to more capillaries + mitochondria (staying longer induration)

what is lactate

produced at glycolic system (2)

• if no oxy, produced lactate through lactate dehydrogenase

• can be used for: oxidized in mitochondria, can be transmitted to lactate shuttle to be oxidized, lactate can convert into glucose → gluconeogenesis

anaerobic energy expenditure: lactate threshold

• lactate threshold: point at which blood lactate accumulation increases markedly → while exercise, accumulation blood lactate, point where it significantly increases (LT)

  • lactate production rate > lactate clearance rate

  • (LPR >LCR) → body not able to clear lactate at same speed that produce which marks the increase

• higher lactate threshold = better endurance performance

• for two athletes with same VO2max higher lactate threshold predicts better performance.

energy expenditure: successful endurance athletes

• high VO2 max

• high lactate threshold (as % VO2 max)

• high percentage of Type I muscle fibers (aerobic cell respiration)

  • (type 1 more successful bc it’s a aerobic cell respiration)

energy expenditure during maximal aerobic exercise notes

• plateau→ the true VO2 max

• EPOC→ O2 consumed > O2 demand in early recovery

  • (EPOC restores ATPCr , lactate →glycogen (gluconeogenesis), body temp CO2 recovery

• O2 deficient→ O2 demand > O2 consumption at early exercise. (Anaerobic pathway for ATP

  • when start of exercise, muscle demand oxy