CVS changes during Exercise
The Cardiovascular system changes to match supply and demand.
Components of the CV system during exercise
Heart rate 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. 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)
Cardiac Output 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 .
Effects of Incremental Exercise on BP
Cardiovascular Adjustments to Exercise
Cardiac Output Components in Trained & Untrained Subjects Untrained Rest 70 72 5.0 Max Exercise 195 113 22.0 Endurance Trained Rest 50 100 5.0 Max Exercise 195 179 35.0 Heart rate Stroke volume Cardiac output Subject/Activity (beats/min) (ml/beat) (L/min)