CV Response to Exercise Flashcards
Mechanical Effects of Endurance Exercise
When muscles are relaxed blood can go retrograde through the valves, and vice versa
During exercise, HR increases, you think that preload might decrease, the skeletal muscle pump will help maintain the preload and venous return to the heart
As you inspire, the chest wall will expand and diaphragm depresses and the pleural cavity becomes more negative to cause the lung to expand along with the atria and ventricles to expand so the pressure decreases in the heart to allow for venous return to increase via this respiratory pump
Metabolic Effects of Exercise
Vasodilation metabolites = adenosine, PO4, lactate, CO2, K+, and H+
Increases the blood flow to the working muscles and the heart to increase O2 delivery to the tissues
Causes SVR (systemic vascular resistance) to decrease overall
Autonomic Effects of Exercise
Cerebral cortex, when you are thinking about exercise before you start exercise, the cortex sends signals to hypothalamus and the BP starts to increase and sympathetic outflow as well
Constricting the vessels to the splanchnic circulation (non-active muscles)
All of these things start before exercise begins
Baroreceptor reflex must kick in to prevent BP from decreasing
Muscle and joint afferents are part of the exercise pressor reflex; as you start to stretch the muscles and joints it will lead to an increase in HR and BP; also stimulated by chemical stimuli; going to get increase in
BP (pressor portion) and as afferents are activated the adrenal glands will cause sympathetic activation of the blood vessels to get constriction
Overall Changes in Blood Flow Due to Exercise
As we start to exercise, flow to skeletal muscles increases by 10x; active hyperemia
Flow to the heart increases about 3x
Flow to the brain doesn’t change because don’t want to decrease and not necessary to increase either
Increase blood flow to skin to dilate and give off extra heart; decrease blood flow to kidneys and splanchnic organs
All of these are because of metabolic and autonomic effects
Exercise ABP
Systolic pressure is increase (200mmHg) based on workload
MAP: slowly increases because baroreceptor reflex is increasing to maintain
Diastolic pressure doesn’t really change or sometimes decreasing because of decrease in systemic vascular resistance (SVR)
Increase in HR, SV, CO, and blood flow to working skeletal muscles and the heart
Decreased SVR, increased systolic BP and MAP, and little to no change in diastolic BP
CV Adaptations to Chronic Exercise
Variable – cardiac remodeling occurs in ~ ½ of trained athletes
Left atrial and/or Ventricular chamber enlargement
Reduced aortic stiffness
Increased number and density of capillaries
Increased vessel cross-sectional area
Increased coronary collateral formation
Increased sensitivity of resistance vessels to vasodilators
Acute Effects of Static Exercise
Isometric (static) exercise
Muscle Blood Flow:
Sustained contractions decrease blood flow in working muscles – compression
Flow to all muscles decreased by SNS
Post-exercise increase in working muscle blood flow – reactive hyperemia
Decreased Renal and Splanchnic blood flow (SNS)
Increased SVR
Increased HR
Increase in thoracic vena cava pressure via compression activates baroreceptor reflex to increase HR and decrease pressure because the Valsalva maneuver increases pressure
ABP, CO, and HR Response to Static Exercise
Arterial BP increases overall
Light to moderate exercise: still increasing
Resting to light/moderate to heavy = all increases (systolic, MAP, and diastolic)
HR and CO increase, but less than occurs during endurance exercise
ABP increases more in resistance exercise than during endurance exercise
Exercise and HF
At rest CHF: HR is higher, SV and CO is lower, MAP is a little lower, VO2 is the same at rest, and arterial – venous is higher because more O2 leaving arteries into the tissues and heart has to work harder
Exercise CHF: one of the hallmarks is intolerance to exercise
Maximal CO is decreased
Max HR is limited by dyspnea and fatigue
Normal increase in SV are reduced
LV failure causes pulmonary HTN because limits RV output by increasing its afterload
Skeletal muscle fatigue from insufficient O2 delivery to working muscles due to reduced perfusion
Reduced arterial pressure because increase in CO is not sufficient to maintain AP as SVR decreases
Exercise Recommendations for CHF Patients
Isometric exercise is discouraged but has not been well evaluated in CHF patients due to increased LV wall stress – unwanted ventricular remodeling
Monitored cardiac rehabilitation and aerobic exercise:
Stable compensated chronic heart failure
Consistently improves functional capacity
Inconsistent improvement of LV function
