EXERCISE AND THE HEART n Acute exercise Single

EXERCISE AND THE HEART n Acute exercise – Single bout of exercise § Steady State (Submaximal) exercise § Maximal exercise n Chronic exercise – Months of conditioning or training – Differences between training and untrained individuals

Cardiovascular Response to Acute Exercise w Heart rate (HR), stroke volume (SV), and cardiac. output (Q). . . w Blood flow (and distribution)…. w Blood pressure … w All of the above change during exercise in order to meet the increase O 2 and energy demands of the muscles.

Heart Rate and Acute Exercise n n n Why does heart rate increase during acute exercise? What causes heart rate exercise? Why does heart rate level off when the exercise intensity levels off? What is the relationship between heart and exercise intensity? How is maximum heart rate estimated?

Heart Rate and Acute Exercise Heart Rate Mile

Heart Rate and Acute Exercise n What causes heart rate to increase? n Parasympathetic n Sympathetic n Catecholamines – Epinephrine – Norepinephrine

Heart Rate and Acute Exercise n Why does heart rate level off when the exercise intensity levels off? n O 2 supply = O 2 demand

Heart Rate and Acute Exercise

Heart Rate and Acute Maximal Exercise What is the relationship between heart rate and exercise intensity? Or, how is heart affected by the intensity of exercise?

Heart Rate and Acute Maximal Exercise n Can be estimated: HRmax = 220 – age in years – – n n n Other formulas: 210 – (0. 65 x age) 208 – (0. 70 x age) – – n For 20 year old, HRmax = 200 For 43 year old, HRmax = 177 For 20 year old, HRmax = 194 For 43 year old, HRmax = 178 202 – (0. 72 x age)

Stroke Volume and Acute Exercise § § Why does stroke volume increase during exercise? What causes stroke volume to increase during exercise? Why does stroke volume stop increasing, or reach its maximum, before a person reaches their maximal effort? What is cardiovascular drift?

Stroke Volume and Acute Exercise • What causes stroke volume to increase during exercise? Hint: There is less residual volume • What is residual volume? • The amount of blood remaining in the heart after a contraction. Also called end systolic volume • • What causes the heart to beat stronger (and thus reduce the residual volume) during acute exercise? Increase sympathetic stimulation and increases in epinephrine and norepinephrine

Stroke Volume and Acute Maximal Exercise Why does stroke volume stop increasing, or reach its maximum, before a person reaches their maximal effort?

Stroke Volume and Acute Exercise n What is cardiovascular drift? happens to the amount of plasma as exercise continues? Increase or decrease? n What affect would a decrease in plasma volume have on stroke volume? n If stroke volume decreases, what would have to happen to heart rate in order to keep blood flow or cardiac output at the same level? (see next slide)

Stroke Volume and Acute Exercise Cardiovascular Drift

Cardiac Output and Acute Exercise n If heart rate and stroke volume increase during exercise, what will happen to cardiac output? n Why is it important that cardiac output increases during exercise? n How can even more blood be sent to the exercising muscles?

Cardiac Output and Acute Maximal Exercise If heart rate and stroke volume increase during exercise, what will happen to cardiac output? Why is it important that cardiac output increases during exercise?

Summary of HR, SV and Q During Acute Exercise Activity Heart rate Stroke volume (beats/min) (ml/beat) Cardiac output (L/min) Resting (supine) 55 95 5. 2 Resting (standing and sitting) 60 70 4. 2 Running 190 130 24. 7 Cycling 185 120 22. 2 Swimming 170 135 22. 9

Blood Flow and Acute Exercise n How can even more blood be sent to the exercising muscles? .

Blood Flow and Acute Exercise

Blood Flow and Acute Exercise n How can even more blood be sent to the exercising muscles? n Vasodilation of arterioles near exercising muscles – Waste products n Vasoconstriction of arterioles near nonexercising muscles and organs. – Sympathetic stimulation

Blood Pressure During Acute Exercise n How would an increase in blood flow through the blood vessels affect blood pressure? n How would vasodilation of the blood vessels affect blood pressure?

Blood Pressure During Acute Exercise Cardiovascular Endurance Exercise n What affect does CV exercise have on systolic blood pressure? n Why? n What affect does CV exercise have on diastolic blood pressure? n Why?

Blood Pressure During Acute Exercise Resistance Exercise n How does resistance exercise affect blood pressure? n Why? n Some BP increases are attributed to the Valsalva maneuver

Blood Pressure During Acute Exercise

Blood Flow and Acute Exercise n What is responsible for the increase blood flow to the muscles during exercise? – Increased cardiac output § Increased heart rate and stroke volume – Redistribution of blood flow § Vasodilation and vasoconstriction What will happen to aerobic energy production as more blood is supplied to the muscles during exercise n How is aerobic energy production measured? n n Oxygen consumption or VO 2

Oxygen Consumption VO 2 is a measure of how much and how fast O 2 is used to make energy (ATP) n In order for VO 2 to increase what must change inside the body? 1. Increase cardiac output 2. Increase extraction of oxygen from the blood n Therefore VO 2 = cardiac output x the amount of oxygen extracted from the blood n

Oxygen Consumption Oxygen Extraction at Rest n Arteries n – 20 ml or oxygen in every 100 ml of arterial blood n Veins – 15 ml/100 ml of blood. How much oxygen did the muscles use? n This amount is call the a-v. O 2 difference. n

Oxygen Consumption n n Cardiac output (Q) = how quickly an amount of blood (e. g. 100 ml) flows to the muscles a-v O 2 difference = amount oxygen of that 100 ml is extracted (or removed) from the blood VO 2 = Q x a-v O 2 difference VO 2 is how aerobic energy production is measured

Oxygen Consumption n What does VO 2 tell us? n How much oxygen is being used to make energy n Resting VO 2 = 3. 5 ml/kg/min n Exercise VO 2 n Maximal VO 2 (VO 2 max)

Exercise VO 2 ing t n i pr = 57 ml/kg/min VO 2 (ml/kg/min) S Running = 38 ml/kg/min Jogging = 24 ml/kg/min Walking = 16 ml/kg/min Time

Maximal VO 2 Results from a graded treadmill test where treadmill speed and elevation are increased every minute.

Maximal VO 2 Values PERCENTILE 20 -29 30 -39 40 -49 50 -59 60+ Men 90 51. 4 50. 4 48. 2 45. 3 42. 5 50 42. 5 41. 0 38. 1 35. 2 31. 8 10 34. 5 32. 5 30. 9 28. 0 23. 1 90 44. 2 41. 0 39. 5 35. 2 50 35. 2 33. 8 30. 9 28. 2 25. 8 10 28. 4 26. 5 25. 1 22. 3 20. 8 Women ►Average values for 18 -22 year olds: 44 to 50 ml · kg-1 · min-1 for males and 38 to 42 ml · kg-1 · min-1 for females