Muscle Metabolism- Sprint and Distance

Question 1

what can muscle use as fuel?

Answer 1

anaerobic or aerobic metabolism

• creatine phosphate
• glucose
• muscle glycogen

aerobic metabolism only

• fatty acids
• ketone bodies
• amino acids

Question 2

where does AMP come from in muscles?

Answer 2

combination of 2 ADP by adenylate kinase- makes an ATP and an AMP

Question 3

what does AMP do?

Answer 3

allosterically activates phosphofructokinase-1 to stimulate glycolysis

Question 4

what does phosphofructokinase-1 do?

Answer 4

stimulates muscle phophorylase b kinase- activates glycogen phosphorylase to break down glycogen

Question 5

when is epinephrine released?

Answer 5

intense exercise

Question 6

what does epinephrine do?

Answer 6

binds beta adrenergic receptors and activates the cAMP/PKA pathway which phospohrylates phosphorylase b kinase, which activates glycogen phophorylase

Question 7

is muscle responsive to glycogen?

Answer 7

no

only epinephrine

Question 8

what 3 things activate muscle glycogenolysis?

Answer 8

AMP
epinephrine
Ca

Question 9

how do nerves stimulate muscle glycogenolysis?

Answer 9

increase cytoplasmic Ca which stimulates glycogen phophorylase b kinase (activates glycogen phosphoylase)

Question 10

what source of energy is used in sprinting?

Answer 10

anaerobic metabolism of muscle only energy supply

Question 11

what are the sources of ATP in sprinting muscle? how long do they last?

Answer 11

ATP pool- 1 sec
creatine-phosphoate pool- 4 sec
glycogen

Question 12

why are fatty acids and ketone bodies not used in sprinting?

Answer 12

not enough time for them to diffuse into tissues

limited perfusion prevents diffusion anyway

Question 13

what is the basis of fatigue when sprinting?

Answer 13

decreased pH

• limits force of contractions
• inhibition of PFK1 which decreases rate of glycolysis

Question 14

what may combat fatigue onset in sprinting?

Answer 14

dietarty creatine and NaHCO3

Question 15

what is the source of energy during prolonged exercise?

Answer 15

aerobic metabolism of muscle glycogen, glucose, fatty acids/ketone bodies (60%)

Question 16

what type of fibers are primarily found in sprinters?

Answer 16

white fibers- few mitochondria

Question 17

what type of fibers are primarily found in endurance athletes?

Answer 17

red fibers- lots of mitochondria

Question 18

what processes are activated by epinephrine?

Answer 18

muscle glycogenolysis
liver glycogenolysis
TAG lipolysis

Question 19

what processes are activated by glucagon?

Answer 19

liver glycogenolysis and gluconeogenesis
TAG lipolysis
NO effect on muscle

Question 20

how is lactate production related to length of exercise?

Answer 20

decreases with increase duration because anaerobic glycolysis is decreased

Question 21

what is the basis of fatigue in endurance exercise?

Answer 21

fuel and O2 depletion

Question 22

what happens when glycogen is depleted?

Answer 22

major energy reduction

switch to fatty acid and blood glucose for energy source

Question 23

what happens as prolonged exercise becomes more vigorous?

Answer 23

muscles get more hypoxic, switch to anaerobic metabolism
fatty acids aren’t used as efficiently and muscle is more reliant on blood glucose (liver glycogenolysis and gluconeogenesis)

Question 24

what are the current recommendations for carbohydrate loading prior to endurance events?

Answer 24

high carb diet during training
increase to 70% carbs and decreased training 2-3 days prior to event
results in 3 times more glycogen stores

Question 25

what is the respiratory quotient?

Answer 25

ratio of CO2 exhaled to O2 consumed

Question 26

how many CO2s are released during aerobic metabolism of glucose?

Answer 26

3- PDH, isocitrate dehydrogenase, and alpha ketogluterate dehydrogenase

Question 27

how many CO2s are released when fatty acids are used?

Answer 27

2- skipped PDH step (isocitrate dehydrogenase and alpha ketogluterate dehydrogenase)

Question 28

what happens to the RQ with increased exercise duration?

Answer 28

decrease because less CO2 is being produced when muscles switch from glycogen to fatty acids for energy