Too much vs. too little exercise?

Question 1

How does an athletes heart differ from a sedentary individual?

Answer 1

• increase mass & volume
• greater LV EDV during rest & exercise
• myocardial cell enlargement
• increased LV cavity (eccentric hypertrophy)
• thickening of walls (concentric hypertrophy)

Question 2

Does the activity an elite athlete engages in dictate the left ventricular mass gain?

Answer 2

wrestlers & shot putters had greatest mass gain

endurance runners & cross-country skiers were second

Question 3

How does oxygen consumption differ for a sedentary individual vs endurance athlete?

Answer 3

for the same given HR, O2 consumption is double for the athlete

O2 consumption
athlete –> 5L/min
sedentary –> 2/2.5L/min

Question 4

How does SV differ for a sedentary individual vs endurance athlete?

Answer 4

athlete –> SV is initially greater at start of exercise and is 1.5x greater than the sedentary individual for a given O2 consumption during exercise

Question 5

What is acute exercise-induced CV risks?

Answer 5

1. Sudden cardiac death
2. cardiac dysfunction & cardiac fatigue

Question 6

What is cardiomyopathy

Answer 6

group of disease that affects heart muscle

Question 7

What is cardiomyopathy

Answer 7

group of disease that affects heart muscle

Question 8

What is channelopathies

Answer 8

group of disease caused by dysfunction of ion channel

Question 9

Explain sudden cardiac arrest

Answer 9

Sudden cardiac death (long distance runners)
- only if underlying cardiac disease
- usually occurred at the last half of a marathon

age:
- most common in middle-aged ppl

Question 10

Explain cardiac dysfunction & cardiac fatigue

Answer 10

for given stimulus, less contraction than supposed to
- due to decreased SV for a prolonged duration of exercise

Question 11

How does prolonged exercise lead to a decrease in cardiac function?

Answer 11

1. increase in HR
   - circulating catecholamines increase
   - b-adrenergic sensitivity decreases
2. increase in heat production
   - blood volume redistribution increases
   - sweat rate increases
   - venous return decreases
3. increase in oxidative stress
   - cardiomyocyte membrane damage increases
4. possible pulmonary congestion

Question 12

What evidence suggest acute myocardial injury?

Answer 12

1. creatine kinase
   - helps catalyze ATP for energy
   - increased levels due to skeletal muscle damage, not acute myocardial injury
2. cardiac troponin’s
   - specific for cardiac muscle so good indicator
   - increases excessing value for AMI diagnosis after exercise

due to:
- increased membrane permeability of mechanical stress
- production of oxidative radicals
- cardiac ischemia

Question 13

How does endurance training & strength training change the structure of the heart?

Answer 13

endurance
- RV dilation
- LV hypertrophy (eccentric)
- both sides get enlarged

strength
- no RV dilation
- LV hypertrophy (concentric)
- only left atrial gets slightly enlarged

Question 14

What is myocardial fibrosis?

Answer 14

accumulation of collagen in extracellular matrix of heart
- common after myocyte injury from ischemia

3 categories
1. reactive interstitial fibrosis
2. infiltrative interstitial fibrosis
3. replacement fibrosis

Question 15

What is a long QT interval?

Answer 15

time between depolarization & depolarization of cardiac ventricles (via C, K, Na ion channels)