this lecture by Dr. Frangos, PT ND, focused on the effects of exercise on the body. we looked at both how the body responds acutely to exercise, as well as how the body adapts long term to regular endurance exercise. acute effects of exercise on the heart include a increase in cardiac output (CO) mainly due to increased heart rate, with only a slight increase in stroke volume (SV), which is dependent on myocardial contractility. regular endurance exercise also increases CO, which is mainly due to increased SV from increased myocardial contractility. other adaptive effects on the heart include a lower resting heart rate and increased maximal oxygen intake. exercise's acute effects on the lungs mainly revolve around an increase in ventilation rate (exercise intensity has a linear relationship with ventilation rate up until moderate intensities, beyond which the relationship becomes supralinear), but also includes an increase in alveolar ventilation for both rate and volume.
hormone release also markedly shifts with exercise, mainly to facilitate efficient utilization of glucose in skeletal muscle. sympathetic stimulation causes release of stress hormones such as epinephrine and cortisol, and insulin release is decreased so that glucose is available in the blood for metabolism. also, thyroid hormones such as T3 and T4 are increased so that metabolism can increase. repeated endurance training causes adaptive changes such as increased insulin receptors on cells, which increases the efficiency of glucose uptake in endurance athletes.
exercise affects skeletal muscle by increasing blood flow to muscle, body temperature due to contraction, and use of creatine phosphate / glycogen to form ATP. additionally, during intense exercise, lactic acid is produced in the muscles and can contribute to a metabolic acidosis, which can be compensated by excreting CO2 through ventilation. sustained endurance exercise increases the oxidative capacity of skeletal muscle through more mitochondria, as well as increasing the size of myofibrils through increased synthesis of myofilaments, and increased fast oxidative-type muscle fibers.
questions
acute effects of exercise on different systems...
1. describe the acute effects of exercise on the heart.
2. what are the increases in HR and SV attributed to?
3. describe the difference in SV and HR as exercise intensity increases to maximum.
4. describe the effect of exercise on mean arterial pressure.
5. describe the acute effects of exercise on the lungs.
6. describe the function of minute ventilation rate vs. exercise intensity.
7. describe the function of the lungs in maintaining pH during exercise.
8. describe how exercise affects hormone release.
9. how does exercise affect thyroid related hormones?
10. describe the effects of exercise on skeletal muscle.
11. describe the acute effects of exercise on metabolism.
12. describe how exercise affects GI function.
adaptive effects of exercise on different systems...
13. how does the heart adapt to endurance exercise?
14. how does endurance training affect hormone release?
15. how does endurance training affect skeletal muscle?
16. how does endurance training affect metabolism?
17. how does endurance training affect bone and connective tissue?
answers
1. drastic increase in CO due to increased HR (small increase in SV) and increased venous return from skeletal muscle pumps and respiratory pump.
2. increased HR due increased sympathetic stimulation of SA node and decreased parasympathetic. increased SV due to increased myocardial contractility.
3. HR continues to max, but SV plateaus relatively early.
4. increases slightly; CO is increased but total peripheral resistance is decreased.
5. increased ventilation rate, increased alveolar ventilation (rate and volume)
6. a linear relationship at low to moderate intensities, then a supralinear relationship.
7. high intensity exercise produces lactic acid in the muscles, which causes metabolic acidosis; the lungs compensate for this by increasing ventilation and excreting CO2 from the blood.
8. causes an increase in hormones related to stress (cortisol, EP, glucagon, GH) due to sympathetic stimulation. also causes a decrease in insulin release (so that glucose can be used as fuel).
9. increased TSH, T4, T3, which stimulates metabolism.
10. increased bloodflow from increased CO, increased body temperature from increased contraction, and increased use of creatine phosphate/glycogen to form ATP.
11. increased liver supply of glucose via glycogenolysis. increased lipolysis causes increase in glycerol and free fatty acids. increased utilization of free fatty acids.
12. decrease in blood flow to GI tract. slower gastric emptying and intestinal absorption. increased caloric expenditure and thus increased appetite.
13. increased contractility of myocardium increases CO, and increased mitochondria increases oxidative capacity. increased efficiency lowers resting heart rate. also, increased maximal oxygen uptake.
14. increased insulin receptor density on cells increases sensitivity to insulin and allows for increased efficiency of glucose transport into muscles.
15. increased mitochondria causes increased oxidative capacity. hypertrophy of muscle fibers due to increased synthesis of myofilaments. increased number of fast oxidative fibers. increased synthesis of glycolytic enzymes. increased capillaries surrounding muscles. finally, increased myoglobin synthesis.
16. improved GI function (motility and elimination in particular), increased BMR, increased endurance from usage of fatty acids, increased WBC count leads to better immune function.
17. decreased chance of injury due to increased strength and density of tissues. decreased joint pain.
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