B6.084 Exercise and Muscle Function

Question 1

what is VO2

Answer 1

rate of oxygen consumption

Question 2

how does rate of oxygen consumption change from rest to max

Answer 2

can increase 12x

Question 3

VO2 equation

Answer 3

VO2 = Q * (a-vO2 diff)

Question 4

how does rate of cardiac output change from rest to max

Answer 4

can increase 4x

Question 5

how does rate of tissue oxygen extraction change from rest to max

Answer 5

can increase 3x

measured by arteriovenous oxygen difference

Question 6

role of skeletal muscle in oxygen consumption

Answer 6

O2 delivery
-muscle blood flow capacity
O2 exchange
-muscle capillarity
ATP production
-mitochondrial content
-mitochondrial function

Question 7

typical resting VO2

Answer 7

3.5

Question 8

what diseases are increased in individuals with low aerobic capacity

Answer 8

CVD
stroke
metabolic syndrome
breast cancer
colon cancer
Alzheimer's
dementia
PCOS
fatty liver

Question 9

max VO2 in aerobically trained individuals vs. sedentary individuals

Answer 9

higher in aerobically trained individuals

aerobic trained age 80 = sedentary age 50

Question 10

VO2 max frailty threshold

Answer 10

18

can no longer perform ADLs below this level

Question 11

how do drugs impact the relationship between exercise and VO2 max

Answer 11

common drugs like statins and metformin can block exercise adaptations (impinge on mitochondrial function)

Question 12

what increases a-vO2 diff

Answer 12

NOT due to elevated arterial O2 content

due to enhanced extraction

Question 13

training adaptations that increase maximal exercise a-vO2 diff

Answer 13

increased muscle blood flow
increased capillaries (primary cause)
increased mitochondria (secondary cause)

Question 14

cellular signals in response to exercise that initiate changes in gene expression

Answer 14

increased AMP/ATP ratio

intracellular Ca2+

Question 15

coordinated response to changes in gene expression with exercise

Answer 15

increased angiogenic growth factors
mitochondrial genes
contractile protein genes
LEAD TO
increased O2 delivery and consumption

Question 16

where are mitochondrial most adaptive

Answer 16

subsarcolemmal mitochondrial respond to exercise/inactivity

Question 17

how do mitochondria change in response to endurance exercise

Answer 17

increased density

higher cristae density (better functioning, more ETC activity)

Question 18

enzymes that increase with exercise training

Answer 18

fat oxidation enzymes

• acyl coA synthetase
• CPT-1
• AMPK
• B oxidation
• TCA enzymes

Question 19

result of increasing fat oxidation with exercise

Answer 19

use more FFAs for energy over carbs bc more fat is available in the body

Question 20

“crossover concept”

Answer 20

with increasing aerobic power/work you increase carb utilization and decrease fat utilization

Question 21

rate limiting steps of glucose uptake by skeletal muscle

Answer 21

supply:
-perfusion
-blood glucose concentration
transport:
-surface membrane GLUT abundance
-glucose gradient
-GLUT activity
metabolism:
-hexokinase activity
-substrate flux

Question 22

function of hexokinase

Answer 22

phosphorylates glucose to keep it in the cell

Question 23

what allows for glucose transport into skeletal muscle

Answer 23

insulin receptor activity activates GLUT4 to translocate to membrane
contraction (exercise) activates GLUT4 to translocate to membrane

Question 24

best recipe for glucose uptake

Answer 24

insulin + exercise

Question 25

how does exercise aid in improving insulin sensitivity?

Answer 25

- increased protein content of GLUT4 - increased protein content and activity of glycogen synthase - increased glycogen storage - muscle fiber conversion to more oxidative/ less glycolytic - increase arteriole dilation with insulin stimulation - changes in the expression of activation of insulin signaling proteins are less consistently found

Question 26

3 types of muscle fibers

Answer 26

type 1: slow twitch red, endurance (oxidative) type 2a: fast twitch red, intermediate (oxidative and glycolytic) type 2b: fast twitch white, power/fatigability (glycolytic)

Question 27

why are slow twitch muscles red

Answer 27

very oxidative, contain a lot of iron

Question 28

fast twitch white motor units

Answer 28

larger with more fibers used in max force activities less mitochondria less capillarity

Question 29

slow twitch red motor units

Answer 29

smaller with fewer fibers used in ADLs finite movements more capillarity

Question 30

effects of exercise on blood vessels

Answer 30

induces: angiogenesis (cap density) arteriogenesis (more branches) artery enlargement (increased endothelium dependent dilation)

Question 31

flow mediated dilation

Answer 31

lower value is associated with increased mortality | measures dilatation as blood flow rushes in after constriction with cuff is removed

Question 32

how do muscles grow?

Answer 32

increased cross sectional area of myofibers

Question 33

what is responsible for early gains in strength

Answer 33

neural adaptations | different motor unit/fiber type activations

Question 34

central neural adaptations

Answer 34

motor cortex activity increases when the level of force developed increases and when new exercises or movement are being learned

Question 35

adaptations of motor units

Answer 35

``` maximal strength and power result from an: -increase in recruitment -rate of firing -synchronization of firing or a combo of the above ```

Question 36

adaptations of NMJs

Answer 36

possible changes with anaerobic training include: - increased area of the NMJ - increased end plate perimeter length and area - greater dispersion of ACh receptors within the end plate region

Question 37

order of recruitment of fibers with increased power exerted

Answer 37

slow twitch red fast twitch red fast twitch white

Question 38

muscle hypertrophy

Answer 38

increased size and number of actin and myosin fibers | NO CHANGE IN NUMBER OF MUSCLE FIBERS