energy expenditure

• Relating to how much energy is produced and the sum of chemical reactions in the body

• TDEE: total daily energy expenditure

  • Resting EE (energy expenditure): energy used in sedentary

  • Activity EE

    • Exercise: structured workout

    • NEAT: non exercising activity thermo-something… physical activity, walking around activity outside of exercise

    • Thermic effect of food

• Thermic effect of food: per 100 kcals consumed of each macronutrient

  • Protein: 20-30

  • Carbs: 5-10

  • Dietary fat: 0-3

• Measurement of energy expenditure

  • Direct calorimetry

    • Efficiency of the body is about 30% ATP production

    • About 70% is lost as heat

  • Heat production increases with energy production

    • Exercise in a sealed chamber

    • Water flows through the walls

    • Increased body temperature increases water temperature

• Direct calorimetry

  • Pros: most accurate, good indication of resting metabolic measurements

  • Cons: expensive, slow, limitations with exercise equipment, human sweat causes errors, not practical or accurate for exercise

• Indirect calorimetry

  • Expired gas analysis, doubly labeled water, other

• Doubly labeled water

  • Can be used in wide range of individuals

  • An isotope is ingested (deuterium 2H and oxygen-18 18O)

  • 7-14 day period and urine samples are collected daily

  • Differences of elimination rates of isotopes is equivalent to CO2 production (98% accuracy)

• Expired gas analysis

  • Can be measured using a metabolic cart or Douglas bag technique

• How do we measure energy expenditure using indirect calorimetry

  • 1. Volume of oxygen consumption (VO2)

2. Volume of carbon dioxide expiration (VCO2)

• VO2 = volume of oxygen inspired- volume of oxygen expired

• VCO2 = volume of CO2 expired- volume of CO2 expired

• Measure volume of inspired oxygen by the fraction oxygen in the air (same

for carbon dioxide), but fraction of inspired to expired may be different!

1. Haldane Transformation

• VO2 = (VE) x {[1-(FEO2 + FECO2) x (0.265)] − (FEO2)}

• Equation used in the metabolic cart!

• Respiratory exchange ratio

  • Estimated amount of fuel usage from CHO and fats during exercise based on chemistry

  • RER=VCO2/VO2

  • Respiratory quotient=RQ (respiratory quotient)- cellular level measurement

  • How much oxygen is used to fully oxidize CHO and fats

• CHO and fat oxidation

  • RER: respiratory exchange ratio

    • Volume of expired CO2/volume of inspired O2

  • RER for 1 molecule glucose=1.0

6 O2 + C6H12O6 -> 6 CO2 + 6 H2O + 32 ATP

• RER = VCO2 / VO2 = 6 CO2/6 O2 = 1.0

This one is more efficient

• RER for 1 molecule palmitic acid = 0.70

• 23 O2 + C16H32O2 -> 16 CO2 + 16 H2O + 106 ATP

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

• Caloric equivalent we typically use to calculate caloric expenditure: 5 Kcals/L O2

• Limitations of indirect calorimetry

  • Overestimation of CO2 production

  • RER inaccurate for protein oxidation

  • RER>1.0 may be inaccurate due to excess lactate production

  • Gluconeogenesis is responsible for RER < 0.70

• Resting energy expenditure

  • 1 MET=3.5 ml/kg/min

  • Metabolic rate- rate of energy use by body

  • Typical responses at rest

    • 0.8 RER, about 0.3 L/min

    • About 2000 kcal/day

• Submax exercise: a normal exercise that isn't a max

• Maximal exercise

  • VO2 max, point where oxygen consumption doesn’t increase with higher intensity

  • GXT: graded exercise test, vo2 max

  • Best measurement of aerobic fitness, gold standard

  • Not best predictor of endurance performance

  • Plateaus after about 8-12 weeks of training

    • Performance improves

    • More training allows athlete to compete at higher percentage of VO2 max

• Factors determining endurance performance

  1. High vo2 max

  2. High lactate threshold (as % vo2 max))

  3. High economy of effort

  4. High percentage of type 1 muscle fibers/type 2a

• Excess postexercise oxygen consumption (EPOC)

  • O2 demand> o2 consumed in early exercise

    • Body incurs o2 deficit

    • O2 required-o2 consumed

    • Occurs when anaerobic pathways used for ATP production

  • O2 consumed> o2 demand in early recovery

    • Excess postexercise o2 consumption (EPOC)

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

• Lactate threshold

  • Lactate production is higher than lactate removal

  • Point at which blood lactate accumulation higher markedly

    • Lactate production rate>lactate clearance rate

    • Interaction of aerobic and anaerobic systems

    • Good indicator of potential for endurance exercise

  • Usually expressed as percentage of vo2 max

• Exercise economy

  • As athletes become more skilled, use less energy for given pace

    • Independent of vo2 max

    • Body learns energy economy with practice

  • Multifactorial phenomenon

    • Economy higher with distance of race

    • Practice-> better economy of movement (form)

    • Varies with type of exercise (running vs swimming)