KIN 210 final part 3 CDV responses to exercise

msu

Cardiovascular Responses to Acute Exercise

• increases blood flow (ie. oxygen) to working muscle

• involves altered heart function, peripheral circulatory adaptations

Fixed Workload Exercise

the intensity (velocity in running, power output in cycling) of the exercise does not change across time during the bout.

Fixed Workload Exercise example

running on the treadmill at 8mph for 40 minutes without changing the speed

Progressive/Graded Exercise

the intensity of the exercise slowly increases across time during the bout of exercise, typical approach to VO2max testing.

Progressive/Graded Exercise example

start running at 3.5mph on the treadmill and increase the speed by 0.5mph every 2 minutes

Interval Exercise

intensity of exercise increases and decreases across the duration of the bout

Interval Exercise example

walk for 2 minutes, sprint for 30 seconds, walk for 2 minutes, repeat

Calculation of tissue O2 consumption depends on:

• blood flow to the tissue

• O2 extraction by the tissue

VO2 = Q x (arterial-venous) O2 difference

VO2 = HR x SV x (a-v) O2 difference

Maximal HR (HRmax) is…

highest HR achieved in all-out effort to volitional fatigue

• highly reproducible

• slight decline with age

• estimated HRmax = 220 - (age in years)

Steady-state HR is…

point of plateau, optimal HR for meeting circulatory demands at a given submaximal intensity

• if intensity increases, so does steady-state HR

• adjustment to new intensity takes 2 to 3 min

Stroke Volume relative to CDV response to exercise

• Increases with intensity to 40%-60% VO2max

• (beyond this, plateau to exhaustion, possible exception: elite endurance athletes)

• Maximal exercise SV ~ double standing SV

a-VO2 difference CDV response to exercise

• Material oxygen content = 18 mL O2 / 100 mL blood

• Venous oxygen content = 11 mL O2 / 100 mL blood

a-VO2 difference = 7 mL O2 / 100 mL blood ~40% O2 extraction

a-VO2 difference during exercise: Arterial oxygen content ______ even as exercise becomes more difficult.

stays the same

a-VO2 difference during exercise: Blood returning to the heart (mixed venous content) is ____ as exercise becomes more difficult.

lower

T/F - a-VO2 difference is greater as exercise becomes more difficult.

True

Effects of Aerobic Fitness-Heart Rate: Heart rate at a submaximal level (see 100 Watts) is _____ if a person is more fit.

lower

Effects of Aerobic Fitness-Heart Rate: Maximal HR is similar as long as both people are the same age, but HRmax happens at a higher speed/power output in ____ people. 

more fit

Blood flow redistribution:

↑ cardiac output → ↑ available blood flow

↑ blood flow redirected to areas with greatest metabolic need (exercising muscle)

• Blood shunted away from less active regions by sympathetic vasoconstriction

─            Splanchnic circulation liver, pancreas, GI)

─            Kidneys

Blood flow:

Local vasodilation permits additional blood flow in exercising muscle.

As temperature rises, skin _____ also occurs.

vasodilation

Blood Pressure during Exercise

During endurance exercise, increase in mean arterial pressure (MAP)

• Systolic BP ↑ proportional to exercise intensity

• Diastolic BP slightly ↓ or slightly ↑ (at max exercise)

MAP =

Q x total peripheral resistance (TPR)

• Q ↑ TPR ↓ slightly

• Muscle vasodilation versus sympatholysis

Myocardial oxygen consumption (RPP)  ____________ (blood pressure during exercise)

increases

Resistance exercise can cause periodic, large increases in blood pressure.

• Up to ___/___ mmHg

• Common during Valsalva

480/350

CDV responses to exercise: H+/Lactate

• A primary by-product of metabolism in glycolysis, Kreb’s Cycle, ß-oxidation of fats, and the electron transport chain are Hydrogen Ions.

• Typically, H+ are buffered by the bicarbonate buffering system

• Bicarbonate is produced by the the kidneys , and reabsorbed into the blood in response to buildup of H+ ions.

• This system works really well at low-intensities, but is a bit too slow as exercise becomes more intense.

Carbonic acid-bicarbonate buffer system

HCO3- + H+    ↔   H2CO3   ↔ H2O + CO2

Minute Ventilation =

Respiratory Rate x Tidal Volume

Minute ventilation _____ steadily as intensity increases, and most rapidly after the ventilatory threshold (moderate exercise).

increases

During light to moderate exercise, large increases in _____ occur but plateaus as exercise becomes more intense.

tidal volume

Breathing frequency (breaths per minute) increase slowly over time, but is most important between ______ exercise intensity.

moderate and maximal

Ventilation ____ proportional to metabolic needs of muscle.

increase

At low exercise intensity, only tidal volume _____.

increases

At high exercise intensity, rate also _____.

increases

Ventilation recovery after exercise delayed

• recovery of minute ventilation usually takes several minutes

• may be regulated by blood pH, PCO2, temperature

Excess lactic acid + sodium biocarbonate in circulation, result: …

excess sodium lactate, H20, CO2

• lactic acid, CO2 accumulated simultaneously

Following acute, intense/maximal exercise, lactate concentration begins to return to _______.

resting values

Clearance of excess lactate is expedited by _____ versus simply just stopping at the end of maximal exercise.

active recovery (very light exercise)

Oxygen Consumption (VO₂) remains elevated for ________ after the end of exercise, depending on intensity.

30 mins to several hours

Excess post-exercise oxygen consumption (EPOC)

is the elevated metabolic rate following the end of exercise

Adults 18-65 years old

150 min of moderate PA per week is key

Dose-response

improved results when exceeding recommendations

Warm-up

• Elevate body temperature

• Increase metabolic rate (VO2)

• Increase joint movement and ROM

• Decrease injury risk

• Typically, 5-10 minutes of slow walking, jogging, or dynamic stretching

Conditioning

• 20-60 minutes of aerobic, resistance/circuit, or sports activities

• Exercise bouts as short as 10 minutes are acceptable as long as individual accumulates 20-60 minutes/day of aerobic exercise

Cool-down

• Gradual recovery (return HR, and BP closer to resting values

• Dissipate body heat

• Active recovery promotes H⁺ and lactate clearance

• Typically, ~5 minutes of slower jogging/walking

Stretching

• At least 10 minutes of stretching, preferably dynamic stretching, performed after the cool-down phase.