The Cardiovascular system changes to match supply and demand.
Components of the CV system during exercise
Measure at the radial or carotid site.
Reflects the amount of work that it is performing to meet the demands of the body with increasing work.
Resting HR: 60 to 80 bts/min.
Anticipatory response-prior to starting exercise just knowing that you are going to have to start exercise.
220-age= predicted Max HR.
Change in HR during Exercise
As exercise begins, Para-SNS withdraws influence.
SNS stimulates heart.
Adrenal gland secretes catecholamines.
Increase in body temperature ,as in intense exercise.
Stroke Volume May increase with increasing rates of work up to intensities of 40% to 60% of maximum exercise. May continue to increase up through maximal exercise intensity, generally in highly trained athletes
Depends on position of body during exercise
upright-SV is less, supine is greater (easier to heart)
Resting is 5.0 L/min-
20 to 40 L/min during exercise.
The need for an increase is to meet the muscle’s demands during exercise.
An increase in HR and SV increases Q, (separate or together)
After 40 to 60% of max, SV plateaus, Q increases due to increase in HR .
Redistribution of Blood Flow
Blood flow to tissues is controlled in relation to tissue needs
Tissue needs may 20-30 fold, but cannot Q that much: 5 L/min 100 -150 L/min ! ? So flow is redistributed between tissues
Muscle blood flow to working skeletal muscle
Splanchnic blood flow to less active organs
Liver, kidneys, GI tract, & also to non-working muscle
Redistribution of Blood Flow During Exercise
Redistribution of Blood Flow Local Systemic Vasodilation Vasoconstriction
Metabolites Epinephrine Adrenal medulla Sympathetic Nervous System overrides
Blood pressure during endurance activities
SBP increases in proportion to exercise intensity.
DBP changes very little during endurance exercise.
There is modest increase in mean arterial pressure .