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Integration of Cardiovascular and Respiratory Function

Integration of Cardiovascular and Respiratory Function. Oxygen Consumption (VO 2 ). Oxygen consumption is the amount of O 2 taken up and consumed by the body for metabolic processes It is equal to the amount of oxygen inspired minus the amount of oxygen expired

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Integration of Cardiovascular and Respiratory Function

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  1. Integration of Cardiovascular and Respiratory Function Oxygen Consumption (VO2) • Oxygen consumption is the amount of O2 taken up and consumed by the body for metabolic processes • It is equal to the amount of oxygen inspired minus the amount of oxygen expired • VO2 is proportional to workload • VO2 (L/min) = [VI (L/min) x %O2 inspired] - [VE (L/min) x %O2 expired]

  2. Oxygen Consumption (VO2) • Theoretically, VO2 is a function of both O2 delivery to and O2 uptake by the working muscle and other tissue • Another way to describe O2 uptake is a-vO2diff, which represents the average amount of O2 in the arteries minus the average amount of O2 in the vena cava • Described mathematically by the Fick Equation • VO2 (L/min) = (SV x HR) x [a-vO2diff (mlO2 / 100 ml of blood)]

  3. Oxygen Consumption (VO2) • Therefore, the maximal rate of oxygen consumption (VO2max) would theoretically occur at maximum SV, HR, and a-vO2diff • VO2max is more properly defined as the maximal amount of O2 that can be taken in and used for the metabolic production of ATP during exercise • To determine VO2max in the lab, VO2 is measured using a metabolic cart and computer system, while the participant performs incremental exercise to exhaustion

  4. Oxygen Consumption (VO2) • Such exercise can be performed using either a cycle ergometer or a treadmill • VO2 max is used as a measure of aerobic fitness, and is indicative of aerobic exercise performance • VCO2 is calculated by measuring the difference between the amount of CO2 expired and inspired • The amount of CO2 produced and O2 consumed varies depending on the type of fuel being used by the working muscle

  5. Oxygen Consumption (VO2) • When fat is being oxidized and used to produce ATP, more O2 is consumed as compared to the amount of CO2 produced • When carbohydrate is the major fuel used to produce ATP, not as much O2 is consumed relative to the amount of CO2 produced • When only carbohydrate is being used, the ratio of VCO2 to VO2 is equal to 1 • RER is close to 0.7 when the main fuel being used is fat • Therefore, RER allows a way to estimate relative contribution of the different fuels used in skeletal muscle during exercise

  6. Limiting Factors for VO2max • The respiratory system could potentially limit VO2max through (a) inadequate ventilation and (b) oxygen diffusion limitations • The cardiovascular system could limit VO2max because of (a) inadequate blood flow and/or cardiac output, or (b) inadequate oxygen-carrying capacity (hemoglobin concentration) • Within the working muscle, a lack of mitochondria and the metabolic systems involved with the useof O2 could also potentially limit VO2max

  7. Limiting Factors for VO2max • Exercise physiologists are supporting the notion that it is the cardiovascular system that limits VO2max in healthy people • It appears that the cardiovascular system is unable to meet the demands of the working muscle and deliver an adequate amount of O2 • The limitation to VO2 max within the cardiovascular system appears to be related to cardiac output (Q)

  8. VO2max for Various Sports

  9. The Rest to Exercise Transition • During incremental exercise, pulmonary ventilation initially increases at a rate proportional to the increase in workload • Eventually, a point is reached where ventilation increases much more rapidly than workload • This point is called the VENTILATORY THRESHOLD, and it normally occurs at about 65-85% of VO2 max, depending on the individual’s level of fitness • Increase in ventilation thought to occur because of an increase in LACTIC ACID ACCUMULATION in the blood

  10. The Rest to Exercise Transition • The energy demands of the exercise can no longer be met by only the aerobic metabolic systems • Hence, the anaerobic system are also used to meet the increasing energy requirements of the exercise • Eventually, a point is reached where blood lactate concentrations rise exponentially, resulting in very high concentrations • This point is referred to as the LACTATE THRESHOLD

  11. Lactate Threshold

  12. The Rest to Exercise Transition • When blood lactate levels begin to accumulate rapidly, this is referred to as the ONSET OF BLOOD LACTATE ACCUMULATION (OBLA) • With proper aerobic training, the OBLA curve can be shifted to the right such that OBLA occurs later and during higher levels of intense exercise

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