KIN 226 12-17 PDF - Cardiovascular Responses To Acute Exercise

Achange Colour Calculate TPR. A person has a: Y (SBP-DBP) + DBP Q = HR XSV TPR = MAP/Q...

Achange Colour Calculate TPR. A person has a: Y (SBP-DBP) + DBP Q = HR XSV TPR = MAP/Q MAP = ~ at rest BP = 120/90 mmHg MAP = /3(120 90) - + 90 = 80x60 = 100mmHg/4 8 L/min. HR = 80 = 4 S. 20 8 TPR units 100mmitg = = SV = 60. Maximal Oxygen Consumption: greatest amount of oxygen that the body can take in, transport, and utilize during exercise. L/min (absolute) or ml/kg/min (relative Output of heart VO2max = Qmax * A-voz diff max VOz max = SVXHRXA-VOz diff max difference in O2 between arteries & veins = muscle z utilization Limits to VO2 Max Respiratory system: O2 diffusion, ventilation, a-VO2 diff Cardiovascular system - Central factors: Q = SV x HR, arterial blood flow, Hb concentration - Peripheral: blood flow to non-exercising regions, muscle blood flow, capillary density, O2 extraction and exchange Muscle/metabolism: myoglobin, enzymes, energy stores and delivery, mitochondrial size and number Delivery of oxygen (Q): not utilization, MAIN LIMITED FACTOR Genetics (25-40%): may explain individual differences in training adaptations, fibre types CARDIOVASCULAR RESPONSES TO ACUTE EXERCISE PART 1 Cardiac Output: amount of blood pumped by the heart during a one minute period. SVX - R = pushing blood out x rate at which heart pumps At rest: Average make ~5L/min Average female ~4L/min Direct Fick Method M//min M1 2 min 100 X depends - - on units used a -VO2 diff ml per looml of blood A person consumes 250 ml O2 and the a-VO2 difference is 5 ml per 100 ml blood. What is Q? = 250m/02 5 litres - x 100 = 5000ml blood = blood 5 m/0z Q will increase with increasing demand of the system  CV responses to aerobic exercise depends on intensity and duration of the exercise. Steady state exercise: when the energy expenditure provided for exercise is balanced with the entry required (plateau reached) * Incremental exercise: keep increasing the intensity, no plateau Line of best Fit Exercise Intensity: oxygen uptake (L/min), % VO2 max, % HR max (220-age) Max HR Equation will in this class use 220-age verestimates yr olds underestimates in -. , SV plateaus because the left ventricle is only so big Untrained charcteristics of Q Endurance athletes characteristics of Q HR ~ 70 bpm HR ~ 50 bpm SV ~ 71.4 mL SV ~ 100 ml More blood ejected heart so has to beat less Mechanisms for Endurance Athletes Increased vagal tone with decreased sympathetic drive Increased blood volume Increased myocardial contractility and compliance of left ventricle Cardiac output increases rapidly during transition from rest to exercise. Increased cardiac output results in an: Increased SBP DBP does not change MAP rises only slightly, following pattern of SBP CARDIOVASCULAR RESPONSES TO ACUTE EXERCISE: PART 2 Blood Flow during Exercises: CNS: increase Heart: increase Muscle: increase (4-6x) Skin: depends on environmental factors - Ex, sweating —> increase & stay the same Kidney: decrease (rest & digest) Spleen: decrease Liver: decrease G.I tract: decrease Blood pH decreases with exercise. Ad exercise progresses, pH continues to drop due to build up of H+ and lactic acid. Becomes acidic. As intensity more Lactic acid , Exercise = loss of blood plasma, increase hematocrit CV Responses to Sub-Maximal Exercise Q increases and levels out at steady state (metabolic requirements of exercise are met) bCHR & Y SV HR increases until a steady state is reached (sympathetic nervous system act) Stroke volume increase until steady state " return blood to heart SNS decreased afterload venous of , , SBP increases (follows Q), DBP no change, MAP increases slightly P Follows SBP but determined by DBP - , more RPP increases until steady state bc HR &SBP TPR decreases rising significantly--TPR MAP bc - is vasodilation = , and TPR at rest TPR : Sub-maximal exercises TPR AP 100mmHg = = P 20 8 "min" = 100mmHg/ TPR =. mmHg = 20 8. TPRunits = Yin = 7 3 TPRUnits. 4. 8 L/min A-VO2 Diff At rest: a-VO2 diff = 6 ml of O2 20 ml of O2 per 100 ml blood in arteries 14 ml of O2 per 100 ml in blood remaining in veins A-VO2 difference increases progressively with exercise as more oxygen is needed During exercise: 20-4 =16 16 ml of O2 is expelled from the capillaries Factors Affecteding the A-VO2 Differences Redistribution of flow to active tissues during exercise Increased capillary density due to training Increased surface area and O2 extraction Increased number and size of mitochondria Increased oxidative enzymes Vascular and metabolic improvements At Max: 6:1 ratio Q:VO2 For every 6 units of blood, 1 litre of O2 is consumed As O2 consumption increases, more oxygen is extracted = decreased oxygen in venous return = increased A-VO2 difference Cardiovascular Drift: an increase in HR without an increase in exercise intensity. With prolonged sedation stage exercise, blood volume decreases due to fluid shift and redistribution of blood to periphery. Decreases SV due to decreased venous return Increases heart rate. To maintain a constant pace = Q must stay the same, increased HR is in response to SV due to decreased venous return. HR must compensate doe a decreasing SV to maintain cardiac output. Results from dehydration and reduction in SV. CARDIOVASCULAR RESPONSES TO ACUTE EXERCISE: PART 3 Blood flows to tissues in proportion to their metabolic activity by constricting to other areas. Never steal from heart, skin and brain CV Responses to Near-Max Exercise Q increase HR increases in response to SV because SV is decreasing SV increases but may decrease after due to blood volume loss BP increase RPP increase TPR decrease  ↑ Intensity and HR doesn't CV Responses to Incremental Maximal Exercise change ? Linear relationships between intensity and Q, VO2, HR, SBP, RPP You hit max HR No change in DBP therefore slight increase in MAP Inverse relationship between intensity and TPR SV increases linearly and then plateaus at 45-50% max because LV can only stretch so much. Upper vs Lower Body based VO2 values ~ therefore you not base exercise prescription on lower body Principle of specificity Upper body exercise: lower stroke volume and higher heart rate than lower body exercise (greater physiological strain) Increased sympathetic input (increase HR) Lower venous return (decrease SV because there is no activation of muscle pump) Recruitment of more torsion muscles (to stabilize) SBP, DBP, TPR and RPP are higher in upper vs lower BP change due in part by sympathetic stimulation - BPEHR VO2 max is higher 20-30% lower in upper body exercise (smaller muscle mass of upper body = & High VO2 both upper lower max cross-country skiing = = CV Responses to Sustained Static Exercise Depends on intensity and duration Q increases (mainly due to increased HR SV remains constant at low intensity, decreases at high intensity Why ? Decreased LVEDV preload) high intrathoracic pressure - - - Increased LVESV Patterload - Arterial pressure SBP & DBP increase therefore ↑ MAP CV Responses to Resistance Exercise Isometric and dynamic air contractions Increase in HR No change in SV Small increase to Q No change in SV but ↑HR , Large increase in blood pressure Valsalva manuever: during heavy lifting and stabilization of torso, forced expiration. During strain: at start slight ↑ BP followed by significant ↓ BP due to an ↑ intrathoracic pressure (collapses veins and thus ↓ venous return and SV) Release of strain: abrupt and significant overshoot ↑ in BP