Lab 2: Metabolic Rate Flashcards
What does the term metabolism reflect?
all chemical and cellular reactions, as well as mechanical work that occurs in living cells
What type of reactions yield energy?
catabolic
What type of reactions require energy input?
anabolic
What is the second law of thermodynamics?
two isolated systems in contact with each other, which differ in any way (temp, density, or pressure) will equalize if given the opportunity
How can the rate of heat loss be measured when humans transform energy to do work?
as a reflection of the metabolic rate of an organism
How is metabolic rate measured?
direct or indirect calorimetry
What variable does a calorimeter measure (and in what unit)?
heat in calories
What is a calorie?
the amount of heat required to raise the temperature of 1 gram of water by 1 degree celsius
How does a direct calorimeter work?
1) subject placed in chamber surrounded by insulated water jacket
2) thermometers in the water jacket measure temperature changes in the water
3) knowing the specific heat of water ( 1cal/deg*g) and the mass of water in the jacket (g), the heat loss (C) from the subject to the walls of the chamber can be calculated
What does the direct calorimeter procedure provide a measurement of?
all heat production in the body including both aerobic and anaerobic metabolism
When can indirect calorimetry be used?
when metabolism is predominantly aerobic
How does an indirect calorimeter work?
measures oxygen uptake to indirectly determine metabolic rate
What factor changes the relationship between oxygen consumption and energy production?
the substrate utilized (carb, fat, or protein)
What is open circuit spirometry?
determines the rate of oxygen uptake (VO2) by subtracting the amount of oxygen expired (VEO2) from the amount of oxygen inspired (VIO2)
What is the Douglas bag technique?
subject breathes through mouthpiece attached to a two-way valve (Daniel’s valve) that permits the entry of atmospheric air on the inspired side and the removal of expired air through the other
How is the volume of expired air collected via the Douglas bag technique?
collected into plastic douglas bags and analyzed for the concentrations of fractional expired oxygen and carbon dioxide using gas analysis machines (PARVO)
How is the volume of expired air determined in the douglas bag technique?
using a volumeter
How is the inspired minute ventilation calculated?
by assuming the amount of nitrogen inspired equals the amount of nitrogen expired
What factors do we need to determine the rate of oxygen consumption?
-volume of expired air (pulmonary ventilation in L/min)
-fraction of expired oxygen (FeO2)
-fraction of expired carbon dioxide (FeCO2)
-room temperature and barometric pressure (required for standardization of different environmental conditions)
What variables are always known by the technician when measuring oxygen consumption?
-fraction of inspired oxygen (FiO2) = 0.2093
-fraction of inspired carbon dioxide (FiCO2) = 0.0003
How is the expired minute ventilation measured and what problem does it pose?
expired minute ventilation is measured as it comes out of mouth from the lungs, it is saturated with water vapor and is at ambient temperature and pressure (ATPS)
To fix the problem posed by minute ventilations collected in Douglas bags, what is done?
all expired minute ventilations collected in a Douglas bag are corrected to a dry gas and standard temperature and pressure (STPD) using a correction factor based on ambient conditions
Ve(STPD) =
Ve(ATPS) x STPD correction factor
what is gross mechanical efficiency (ME)
the ratio of mechanical power (mechanical work rate) to metabolic power (rate of energy expenditure required to maintain this specific mechanical work rate)
normal values of ME for humans
0-30%
what does ME depend on?
intensity, exercise modality, contraction type, muscle fiber type, etc.
what is the main component of total daily energy expenditure (TDEE)
basal metabolic rate (BMR)
what does BMR include? what proportion of TDEE does this account for?
energy used to sustain all cellular, chemical, and mechanical work at rest (60-70% of TDEE)
what is the thermic effect of food (TEF)? what proportion of TDEE does this account for?
energy cost for the digestion of food and absorption of nutrients (10% of TDEE)
what are the two subcomponents of total daily activity thermogenesis (TDAT)?
exercise activity thermogenesis (EAT) and non-exercise activity thermogenesis (NEAT)
what does EAT account for?
the energy expenditure associated with sport-specific exercising
what does NEAT account for?
energy cost of all other forms of physical activity
what is the dynamic energy balance equation?
rate of change of energy stores = rate of change of energy intake -rate of change of energy expenditure
