EXSC 460 Chapter 8 Notes PDF

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CARDIORESPIRATORY RESPONSES TO ACUTE EXERCISE CHAPTER 8 EXSC 460

NOTA BENE §If you need a review of cardiovascular and respiratory systems, you are encouraged to read chapters 6 and 7.

§Always looks at the graph axes and captions!

CHAPTER OBJECTIVES – CARDIOVASCULAR VARIABLES 1. Heart Rate (HR)

REST

2. Stoke Volume (SV) 3. Cardiac Output (Q) 4. Fick Equation 5. Blood Pressure (BP) 6. Blood Flow 7. Fluid shifts

ACUTE SUBMAXIMAL STEADY -STATE AEROBIC ACUTE MAXIMAL INCREMENTAL AEROBIC

RESISTAN CE EXERCISE

CHAPTER OBJECTIVES – RESPIRATORY VARIABLES 8. Pulmonary Ventilation (VE)

REST

9. Ventilatory Threshold 10. Respiratory regulation pH • Chemical buffers

ACUTE SUBMAXIMAL STEADY-STATE AEROBIC ACUTE INCREMENTAL MAXIMAL AEROBIC

HEART RATE – RESTING • Best time to measure • Average resting values • Bradycardia and tachycardia • Sex differences • Explanations

• Easily affected • Anticipation or stress • Environment • Stimulants • Dehydration

HEART RATE – MAXIMUM • Ways to determine • Declines with age • Onset, rate, explanation

HR RESPONSE TO EXERCISE

Response to aerobic exercise proportional to intensity Time to attain steady state HR affected by intensity & training statuss

EXTRINSIC REGULATION OF HR • Parasympathetic innervation • Effect on intrinsic HR

• Mechanisms allowing ↑ HR with onset of exercise • Linear relationship between HR and exercise intensity • Strongest >110 bpm

YMCA SUBMAXIMAL GXT

HR RESPONSE – EFFECT OF FITNESS • Measurement of HR during submaximal aerobic capacity testing to estimate VO2max • Plot & extrapolate; use metabolic equations to estimate VO2max

• Response to submaximal aerobic exercise reflective of training status

Incremental submaximal aerobic capacity test

STROKE VOLUME • Volume of blood ejected from ventricles with a single contraction • Difference between end diastolic volume (EDV) and end systolic volume (ESV)

STROKE VOLUME VENTRICULAR FILLING CAPACITY

• Occurs during diastole • Influenced by

VENTRICULAR EMPTYING CAPACITY

• Occurs during systole • Influenced by

• Ventricular distensibility • Volume blood returned to heart

• Determine EDV (pre-load) • Volume stretches myocardium and affects force of subsequent contraction to empty ventricles

• Ventricular contractility • Aortic mean pressure (afterload)

• Affects force with which blood is ejected • Force facilitates flow

• Frank-Starling’s Law

VENTRICULAR FILLING CAPACITY • Ventricular distensibility • Volume of blood returned to heart • Processes that facilitate venous blood • 1 • 2 • 3

VENTRICULAR EMPTYING CAPACITY • Ventricular contractility • Processes that facilitate contraction • 1 • 2

• Aortic mean pressure • Effect of greater versus lesser afterload on emptying

• Process that reduce afterload • 1

SV RESPONSE TO EXERCISE

Despite less time to fill

Mechanisms explaining acute increase at lower versus higher intensities

STROKE VOLUME – EFFECT OF BODY POSITION • Resting values in supine/recumbent positions • Explanation

• Exercise-induced increase in supine/recumbent positions • Optimal position for cardiovascular recovery ?

Men's Health (2015)

CARDIAC OUTPUT (Q)

Major purpose of increased Q during exercise

Q RESPONSE TO EXERCISE

How does Q increase above 40-60% VO 2 max?

Slight, transient decrease in SV upon standing causes transient decrease in BP which triggers baroreceptor reflex

REST & MAXIMAL AEROBIC EXERCISE

Less trained

HRrest

SVrest

Qrest

HRmax

SVmax

Qmax

(bpm)

(ml/beat)

(L/min)

(bpm)

(ml/beat)

(L/min)

83

60

185

100

18.5

50

100

180

200

36.0

Highly trained

Q – REDISTRIBUTION DURING EXERCISE EXTRINSIC CONTROL OF BLOOD FLOW

BLOOD PRESSURE (BP) • Optimal resting values • Typical response during aerobic exercise • Systolic Pressure • Incremental vs. steady-state moderate duration • Potential response to prolonged steady-state • Mechanisms for potential decrease & associated problems

• Diastolic Pressure • Incremental and steady-state moderate duration

• Necessity of ↑ SBP to support exercise • Facilitates blood flow through vasculature • Determines volume of plasma that shifts from systemic circulation (intravascular space) to muscle (interstitial space)

BP RESPONSE – INCREMENTAL AEROBIC EXERCISE

Balance between constriction and dilation in upper and lower body

BP RESPONSE – RESISTANCE EXERCISE • Higher muscular forces on intramuscular blood vessels • Increases TPR • Sum total of all resistance to blood flow outside aortic valve

BP RESPONSE – DYNAMIC RESISTANCE EXERCISE

Performing maximal effort lifts, going to failure, and perfor ming the Valsalva maneuver all heighten the blood pressure response to resistance exercise.

STATIC UPPER BODY RESISTANCE versus DYNAMIC LOWER BODY AEROBIC

VALSALVA MANEUVER ADVANTAGES

DISADVANTAGES

• ↑ thoracoabdominal pressure

• Exerts compressive forces on heart

• Reduce effort required of spinal stabilization muscles • Correct posture and body alignment

• Compromises venous return • Compromises systemic blood flow • Extreme momentary elevation in arterial pressure to overcome elevated pressures & compensate for reduced venous return • Dizziness, blackouts, vessel rupture

VALSALVA MANEUVER

• Eddie Hall

• Mikhail Shivlyakov

BLOOD FLOW • Extrinsic control • (At rest), sympathetic nervous system maintains tonic level of vasoconstriction to all tissues to ensure adequate blood pressure • Passive vasodilation • Active vasodilation*

• Intrinsic control • Exercise metabolism • Myogenic contraction • Endothelium-mediated vasodilation

PLASMA VOLUME • Exercise moves fluid from systemic circulation to muscle fiber • BP pushes fluid into cell • Metabolic by-products pull fluid into cell

• Purposes of fluid shift • Perfuse muscle with O2ated blood • Dilute metabolic by-products

EXERCISE-INDUCED FLUID SHIFTS • Exercise • Plasma moves from intravascular space to interstitial space • Driven by pressures • Results in increased osmotic/oncotic pressure of intravascular fluid

• Exercise accompanied by sweating • Additional plasma losses primarily from interstitial fluid • Results in increased osmotic pressure of interstitial fluid → additional water movement from intravascular to interstitial • 10-15% ↓ plasma volume compromise the cardiovascular system

Reductions in plasma volume compromise stroke volume, blood pressure, exercise capacity, and ability to thermoregulate.

COMPETITION FOR Q DURING EXERCISE

VO2 drift may also occur

CARDIOVASCULAR DRIFT

Explanations for cardiovascular drift

CARDIOVASCULAR STRAIN

BLOOD – OXYGEN CONTENT

BLOOD – OXYGEN CONTENT

Blood is always saturated with oxygen, except in very few circumstances such as EIAH, which results from high Q and high V E .

ALTITUDE TRAINING MASKS • Marketed as devices that simulate high altitude training • Do not decrease the concentration of oxygen in air one breathes • Do increase resistance to respiration • Strengthen respiratory muscles and perhaps improve breathing mechanics

PULMONARY VENTILATION • Initial Phase

• Respiratory control centers • Receive input from various receptors once exercise begins

• Second Phase

• By-products of aerobic metabolism (H+, PCO2) • Chemoreceptors stimulate inspiratory center to increase rate and depth of respiration • Brain, carotid bodies, lungs, muscles

• Recovery

• Various metabolic processes, H +, CO2, heat

Steady state of varying intensities

VENTILATORY THRESHOLD • Pulmonary ventilation increases linearly with intensity • Low intensity via • High intensity via

• Ventilatory Threshold • Coincides with lactate threshold • Metabolic acids bind with bicarbonate and form CO2

• Reflects disproportionate increase in CO2 production relative to O2 consumption • RER implications Progressive aerobic

ACID-BASE BALANCE • Chemical buffers • Provide means to acutely regulate pH • Transport acids to lungs or kidney

pH & LACTATE RECOVERY...