Integration of Integration of Cardiovascular and Cardiovascular and Respiratory FunctionRespiratory Function

Oxygen consumption is the amount of OOxygen consumption is the amount of O22 taken up and consumed by the body for taken up and consumed by the body for metabolic processesmetabolic processes

It is equal to the amount of oxygen inspired It is equal to the amount of oxygen inspired minus the amount of oxygen expiredminus the amount of oxygen expired

VOVO22 is proportional to workload is proportional to workload

VOVO22 (L/min) = [V (L/min) = [VII (L/min) x %O (L/min) x %O22 inspired] - inspired] - [V[VEE (L/min) x %O (L/min) x %O22 expired] expired]

Oxygen Consumption (VO2)

Oxygen Consumption Oxygen Consumption (VO(VO22))

Theoretically, VOTheoretically, VO22 is a function of both O is a function of both O22 delivery to and Odelivery to and O22 uptake by the working muscle uptake by the working muscle and other tissueand other tissue

Another way to describe OAnother way to describe O22 uptake is a-vO uptake is a-vO22diff, diff, which represents the average amount of Owhich represents the average amount of O22 in in the arteries minus the average amount of Othe arteries minus the average amount of O22 in in the vena cavathe vena cava

Described mathematically by the Fick EquationDescribed mathematically by the Fick Equation VOVO22 (L/min) = (SV x HR) x [a-vO (L/min) = (SV x HR) x [a-vO22diff (mlOdiff (mlO22 / 100 / 100

ml of blood)]ml of blood)]

Oxygen Consumption Oxygen Consumption (VO(VO22))

Therefore, the maximal rate of oxygen Therefore, the maximal rate of oxygen consumption (VOconsumption (VO22max) would theoretically max) would theoretically occur at maximum SV, HR, and a-vOoccur at maximum SV, HR, and a-vO22diffdiff

VOVO22max is more properly defined as the max is more properly defined as the maximal amount of Omaximal amount of O22 that can be taken in that can be taken in and used for the metabolic production of and used for the metabolic production of ATP during exerciseATP during exercise

To determine VOTo determine VO22max in the lab, VOmax in the lab, VO22 is is measured using a metabolic cart and measured using a metabolic cart and computer system, while the participant computer system, while the participant performs incremental exercise to performs incremental exercise to exhaustionexhaustion

Oxygen Consumption Oxygen Consumption (VO(VO22))

Such exercise can be performed using either a Such exercise can be performed using either a cycle ergometer or a treadmillcycle ergometer or a treadmill

VOVO22 max is used as a measure of aerobic fitness, max is used as a measure of aerobic fitness, and is indicative of aerobic exercise performanceand is indicative of aerobic exercise performance

VCOVCO22 is calculated by measuring the difference is calculated by measuring the difference between the amount of CObetween the amount of CO22 expired and inspired expired and inspired

The amount of COThe amount of CO22 produced and O produced and O22 consumed consumed varies depending on the type of fuel being used varies depending on the type of fuel being used by the working muscleby the working muscle

Oxygen Consumption Oxygen Consumption (VO(VO22))

When fat is being oxidized and used to produce ATP, When fat is being oxidized and used to produce ATP, more Omore O22 is consumed as compared to the amount of is consumed as compared to the amount of COCO22 produced produced

When carbohydrate is the major fuel used to When carbohydrate is the major fuel used to produce ATP, not as much Oproduce ATP, not as much O22 is consumed relative to is consumed relative to the amount of COthe amount of CO22 produced produced

When only carbohydrate is being used, the ratio of When only carbohydrate is being used, the ratio of VCOVCO22 to VO to VO22 is equal to 1 is equal to 1

RER is close to 0.7 when the main fuel being used is RER is close to 0.7 when the main fuel being used is fatfat

Therefore, RER allows a way to estimate relative Therefore, RER allows a way to estimate relative contribution of the different fuels used in skeletal contribution of the different fuels used in skeletal muscle during exercisemuscle during exercise

Limiting Factors for Limiting Factors for VOVO22maxmax

The respiratory system could potentially limit The respiratory system could potentially limit VOVO22max through (a) inadequate ventilation max through (a) inadequate ventilation and (b) oxygen diffusion limitationsand (b) oxygen diffusion limitations

The cardiovascular system could limit VOThe cardiovascular system could limit VO22max max because of (a) inadequate blood flow and/or because of (a) inadequate blood flow and/or cardiac output, or (b) inadequate oxygen-cardiac output, or (b) inadequate oxygen-carrying capacity (hemoglobin concentration)carrying capacity (hemoglobin concentration)

Within the working muscle, a lack of Within the working muscle, a lack of mitochondria and the metabolic systems mitochondria and the metabolic systems involved with the useinvolved with the use of Oof O22 could also could also potentially limit VOpotentially limit VO22maxmax

Limiting Factors for Limiting Factors for VOVO22maxmax

Exercise physiologists are supporting the Exercise physiologists are supporting the notion that it is the cardiovascular system notion that it is the cardiovascular system that limits VOthat limits VO22max in healthy peoplemax in healthy people

It appears that the cardiovascular system is It appears that the cardiovascular system is unable to meet the demands of the working unable to meet the demands of the working muscle and deliver an adequate amount of muscle and deliver an adequate amount of OO22

The limitation to VOThe limitation to VO22 max within the max within the cardiovascular system appears to be related cardiovascular system appears to be related to cardiac output (Q)to cardiac output (Q)

VO2max for Various VO2max for Various SportsSports

The Rest to Exercise The Rest to Exercise TransitionTransition

During incremental exercise, pulmonary During incremental exercise, pulmonary ventilation initially increases at a rate proportional ventilation initially increases at a rate proportional to the increase in workloadto the increase in workload

Eventually, a point is reached where ventilation Eventually, a point is reached where ventilation increases much more rapidly than workloadincreases much more rapidly than workload

This point is called the VENTILATORY THRESHOLD, This point is called the VENTILATORY THRESHOLD, and it normally occurs at about 65-85% of VOand it normally occurs at about 65-85% of VO22 max, depending on the individual’s level of fitnessmax, depending on the individual’s level of fitness

Increase in ventilation thought to occur because Increase in ventilation thought to occur because of an increase in LACTIC ACID ACCUMULATION in of an increase in LACTIC ACID ACCUMULATION in the bloodthe blood

The Rest to Exercise The Rest to Exercise TransitionTransition

The energy demands of the exercise can no The energy demands of the exercise can no longer be met by only the aerobic metabolic longer be met by only the aerobic metabolic systemssystems

Hence, the anaerobic system are also used to Hence, the anaerobic system are also used to meet the increasing energy requirements of meet the increasing energy requirements of the exercisethe exercise

Eventually, a point is reached where blood Eventually, a point is reached where blood lactate concentrations rise exponentially, lactate concentrations rise exponentially, resulting in very high concentrationsresulting in very high concentrations

This point is referred to as the LACTATE This point is referred to as the LACTATE THRESHOLDTHRESHOLD

Lactate ThresholdLactate Threshold

The Rest to Exercise The Rest to Exercise TransitionTransition

When blood lactate levels begin to When blood lactate levels begin to accumulate rapidly, this is referred to accumulate rapidly, this is referred to as the ONSET OF BLOOD LACTATE as the ONSET OF BLOOD LACTATE ACCUMULATION (OBLA)ACCUMULATION (OBLA)

With proper aerobic training, the With proper aerobic training, the OBLA curve can be shifted to the right OBLA curve can be shifted to the right such that OBLA occurs later and such that OBLA occurs later and during higher levels of intense during higher levels of intense exerciseexercise