Term
| Define direct calorimetry and indirect calorimetry and describe how they are used to measure energy expenditure. |
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Definition
| Direct calorimetry is the process of quantifying energy production by measuring the body's heat production first described by Zuntz and Hgemann in the late 1800s. This process involves keeping a person in a chamber on a treadmill where their changes in body temperature will alter the temperature of the air in the chamber, as well as the water running through a series of tubes within. Indirect calorimetry is the method of estimating total body energy expenditure by measuring the respiratory exchange of O2 and CO2 in the body. This process relies on oxidative expenditure, so subjects must be in a steady state of aerobic activity to gain an accurate reading, which closely simulates daily activities and exercise. Indirect calorimetry finds its results from the difference between O2 and CO2 concentration to determine oxygen capacity and CO2 production. |
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Term
| What is the respiratory exchange ratio (RER)? Explain how it is used to determine the oxidation of carbohydrate and fat. |
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Definition
| The ratio between the rate of CO2 released (VCO2) and oxygen consumed (VO2). The value can vary depending on the type of fuel being used. For example, FFA's have more carbon and hydrogen than glucose, but with less oxygen. The amount of oxygen needed to oxidize a molecule of carbohydrates or fat completely is proportionate to the amount of carbon in the fuel, so the measurement is reliant on what type of substrate is being used. Fat has more carbon and less oxygen, so the RER of fat measurements would be higher. It ultimately determines the amount of fuel being used by how high or low the RER is. |
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Term
| What are the basal metabolic rate and resting metabolic rate, and how do they differ? |
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Definition
| The BMR is a standardized measure of energy expenditure at rest. Measured in a supine position in a thermoneutral environment immediately after 8 hours of sleep and 12 hours of fasting. The value determined is the minimum amount of energy to carry out essential physiological functions and is generally higher if the body surface area and fat-free mass are high. The RMR is an alternate measurement of metabolism that does not require the standardized conditions of a true BMR. While not as accurate, the RMR typically falls within 5% to 10% of the BMR with the BMR slightly lower. |
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Term
| What is the maximal oxygen uptake? How is it measured? What is the relationship to sport performance? |
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Definition
| The maximal oxygen uptake (VO2MAX) is the maximal limit of a person's ability to increase their VO2. It is considered the single best measurement of cardiorespiratory endurance or aerobic fitness. It is measured by observing the amount of oxygen consumed during prolonged aerobic activity. Those with strong aerobic fitness can uptake more oxygen, which requires more oxygen to achieve their maximum value. In sports, this means those with a higher VO2MAX should be able to perform at a higher pace for a longer period of time. |
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Term
| Describe two possible markers of anaerobic capacity. |
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Definition
| The two possible markers for anaerobic capacity are EPOC, the state immediately after exercise where the body continues to generate an increased amount of O2 intake and CO2 expulsion despite it returning to a resting or low activity state, and the lactate threshold, the point at which blood lactate begins to substantially accumulate above resting concentrations during exercise of increasing intensity. |
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Term
| What is the lactate threshold? How is it measured? What is its relationship to sport performance? |
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Definition
| The lactate threshold is the point at which blood lactate begins to substantially accumulate above resting concentrations during exercise of increasing intensity. It is measured by taking a blood sample at various points of exercise to measure blood lactate to find the relationship between exercise and blood lactate. Perhaps best defined as the point in time during exercise of increasing intensity where the rate of lactate production exceeds the rate of lactate clearance, it's tied to sports performance since those with a higher lactate threshold can maintain a high performance for a longer period of time. This idea usually coincides with a higher VO2MAX. |
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Term
| What is the economy of effort? How is it measured? What is its relationship to sport performance? |
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Definition
| Economy of effort is a person's ability to use less energy performing an activity as they become more skilled. It is measured by comparing two runners with an almost identical VO2MAX and seeing if there is a performance difference between the two despite them being on nearly equal footing when it comes to oxygen production. This ties into sports performance since while there is no specific explanation as to why this is, it shows that a more economical use of one's effort can lead to a greater physical output with less energy used. Ideal for marathon athletes. |
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Term
| What is the relationship between oxygen consumption and energy production? |
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Definition
| The amount of oxygen needed to oxidize a molecule of fat or carbohydrate is generally the same as the amount of carbon in the fuel. Depending on the type of fuel being used for energy production, more or less oxygen would be needed to match with the amount of carbon being used. |
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Term
| Why do athletes with high VO2Max values perform better in endurance events than those with lower values? |
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Definition
| Athletes with a high VO2MAX value perform better in endurance events because they are less susceptible to fatigue and can perform at a higher level for longer. Because of this, they are able to reach their VO2MAX levels, being able to draw energy from more oxygen for a more gradual and sustainable period of time. Those with lower values have less oxygen to draw from, reach their maximum value with less effort, and might become fatigued before reaching their VO2MAX, instead drawing from their VO2PEAK, which is the highest oxygen consumption they could reach while still being below their maximum value. |
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Term
| Why is oxygen consumption often expressed as milliliters of oxygen per kilogram of body weight per minute (ml * kg^-1*min^-1)? |
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Definition
| Oxygen consumption is expressed this way because energy requirements vary with body size. Because of this, VO2MAX measurements must take body weight into account, so the measurement used is able to account for individuals making up a variety of sizes. |
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