Acute metabolic responses to exercise + fatigue

Question 1

What are the 2 main factors determining energy pathway utilisation?

Answer 1

Exercise intensity + Exercise duration

Question 2

What happens to the relative contribution of PCr during the first 30 seconds of a sprint?

Answer 2

Starts off as a large contributor of ATP turnover, however gradually contribtion decreases as Pcr stores are used up.

Question 3

What happens to the relative contribution of the glycolytic system during the first 30 seconds of a sprint?

Answer 3

Has a relatively high contributor of ATP turnover during the first 15 seconds, however glycolysis decreases in the second 15 seconds as stored glycogen is used up.

Question 4

What happens to the relative contribution of oxidative phosphorylation during the first 30 seconds of a sprint?

Answer 4

Contribution starts very low as predominant energy pathways are anaerobic, however as glycogen and Pcr stores deplete, contribution of oxidative phosphorylation becomes greater.

Question 5

What is the RER for glucose?

Answer 5

1

Question 6

What is the RER for representative fatty acid

Answer 6

0.7

Question 7

What causes sarcolemmal depolarization during HIE?

Answer 7

Extracellular K+ accumulation (important for development of fatigue).

Question 8

In terms of K+ accumulation and amount of Na+/K+ pumps, what can training lead to?

Answer 8

• Reduced interstitial K+ accumulation
• Change in the amount of Na+/K+ pumps

Question 9

What does having higher Na+/K+ pump activity do?

Answer 9

It reduced the net loss of K+ from contracting muscles, preserving cell excitability and force production.

Question 10

Define ‘muscle fatigue’

Answer 10

“An exercise induced reduction in the ability of muscle to produce force or power, whether or not the task can be sustained”

Question 11

What are 3 potential contributing factors to skeletal muscle fatigue?

Answer 11

• AP along sarcolemma + T-tubule
• Release of Ca2+ and re-uptake of Ca2+ from ER
• Contractile events at crossbridge

Question 12

How does the triad junction decrease rate of ATP use?

Answer 12

Plays a key role in sensing depletion of cellular ATP levels and reducing Ca2+ release. This decreases rate of ATP use by reducing crossbridge cycling and Ca2+ uptake (2 main sources of ATP hydrolysis).

Question 13

What is the exchange of a phosphate between ATP and PCr catalysed by?

Answer 13

Creatine Kinase

Question 14

What is (most likely) the predominant underlying mechanism of fatigue induced by prolonged endurance exercise?

Answer 14

Reduced CHO availability

Question 15

What muscle fibre type are glycogen and PCr utilization greater in during a 30 second sprint?

Answer 15

Type II

Question 16

Give 2 reasons why lactate production may be advantageous during muscle contraction.

Answer 16

• Allows for regeneration of NAD+
• Cell-to-cell lactate shuttles

Question 17

What do MCT proteins do?

Answer 17

Facilitate transport of lactate and H+ during HIE.

Question 18

How can ROS cause fatigue?

Answer 18

ROS are capable of attacking a variety of biomolecules, causing them to lose function. These biomolecules (in the context of fatigue) are likely to be key proteins involved during contraction.

E.g., NA+/K+ATPase - contributing to role of extracellular K+ accumulation.

Question 19

How may Pi impair force production?

Answer 19

Acts directly on myofibrils, reducing Ca2+ sensitivity as well as reducing SERCA activity (reducing Ca2+ reuptake into the SR).

Question 20

What is the point in creatine supplementation?

Answer 20

• increase resting PCr conc
• increase rate of PCr resynthesis between HI bouts

Question 21

What does HIE do
to lactate and H+ transport?

Answer 21

Enhances transport capacity. Co-transport facilitated by MCT proteins.

Question 22

What is the cell-to-cell lactate shuttle?

Answer 22

Lactate predominantly produced in glycolytic fibres can be shuttled to other cells for use as additional energy substrate.

Question 23

What is it called when lactate transports to the liver?

Answer 23

Cori cycle - glucose produced from lactate helps maintain plasma glucose levels.