Energy use and recovery after exercise

Which pathway generates most ATP in a resting skeletal muscle?

A) Aerobic respiration of fatty acids | B) Anaerobic fermentation of glycogen | C) The phosphagen system | D) Glycolysis of blood glucose

Aerobic respiration of fatty acids

Which enzyme transfers a phosphate group (Pi) from one ADP molecule to another to form ATP during immediate energy demand?

A) Creatine kinase | B) Acetylcholinesterase | C) Myokinase | D) Myosin ATPase

Myokinase

Which enzyme obtains a phosphate group from creatine phosphate (CP) and donates it to ADP to make ATP?

A) Myokinase | B) Creatine kinase | C) Lactate dehydrogenase | D) Calsequestrin

Creatine kinase

What is the combination of ATP and creatine phosphate (CP) collectively called?

A) Glycogen–lactate system | B) Aerobic pathway | C) Anaerobic threshold | D) Phosphagen system

Phosphagen system

How long can the phosphagen system power maximal effort (such as sprinting or weight lifting)?

A) About 6 seconds | B) 30 to 40 seconds | C) 3 to 4 minutes | D) Over 30 minutes

About 6 seconds (or about 1 minute of brisk walking)

What is the point called when muscles exhaust the phosphagen system and transition to anaerobic fermentation, causing blood lactate to rise?

A) Steady state | B) Phosphagen threshold | C) Anaerobic threshold | D) Aerobic limit

Anaerobic (lactate) threshold

How much ATP does the glycogen–lactate system (short-term energy) produce per glucose consumed?

A) 1 ATP | B) 2 ATP | C) 15 ATP | D) 30 ATP

2 ATP (enough for 30 to 40 seconds of maximum activity)

Which energy pathway takes over after about 40 seconds of exercise once the cardiovascular and respiratory systems "catch up" with oxygen delivery?

A) Phosphagen system | B) Anaerobic fermentation | C) Myokinase transfer | D) Aerobic respiration

Aerobic respiration

How much additional ATP does aerobic respiration typically produce per glucose molecule?

A) 30 ATP | B) 2 ATP | C) 6 ATP | D) 15 ATP

30 ATP

During prolonged exercise lasting more than 30 minutes, which fuel becomes the most significant energy source once glucose and glycogen are depleted?

A) Creatine phosphate | B) Lactate | C) Fatty acids | D) Myoglobin

Fatty acids

What is muscle fatigue?

A) Progressive weakness and loss of contractility from prolonged muscle use | B) Sudden involuntary cramping of a resting muscle | C) Permanent tearing of myofibrils | D) Rapid depletion of all cellular ATP

Progressive weakness and loss of contractility from prolonged muscle use

During high-intensity, short-duration exercise, how does potassium K+ accumulation in the T tubules cause fatigue?

A) It blocks ACh receptors on the motor end plate | B) It breaks down myosin heads | C) It lowers membrane potential and interferes with Ca2+ release from the SR | D) It stops glycolysis in the sarcoplasm

It lowers membrane potential and interferes with Ca2+ release from the SR

How does ADP/Pi accumulation contribute to muscle fatigue during intense exercise?

A) ADP speeds up cross-bridge cycling too rapidly | B) ADP slows cross-bridge cycling while free phosphate (Pi) inhibits SR calcium release and myofibril force | C) (Pi) permanently binds to troponin | D) ADP causes excessive sweating and ion loss

ADP slows cross-bridge cycling while free phosphate (Pi) inhibits SR calcium release and myofibril force

What is the primary cause of "hitting the wall" during long-duration, low-intensity exercise?

A) Potassium buildup in T tubules | B) Lactic acid buildup | C) Complete ATP depletion | D) Fuel depletion

Fuel depletion

How does electrolyte loss through sweating contribute to endurance fatigue?

A) It alters the extracellular ion balance enough to reduce muscle excitability | B) It directly digests thin actin filaments | C) It stops blood flow to the liver | D) It prevents myosin from binding ATP

It alters the extracellular ion balance enough to reduce muscle excitability

What causes central fatigue during prolonged endurance exercise?

A) Damaged T tubules in skeletal muscle | B) Lack of oxygen in the lungs | C) Ammonia buildup absorbed by the brain inhibiting motor neurons in the cerebrum | D) Excess creatine phosphate in the cytosol

Ammonia buildup absorbed by the brain inhibiting motor neurons in the cerebrum

Which two former explanations for muscle fatigue have been discredited by recent research?

A) Potassium accumulation and electrolyte loss | B) Total ATP depletion and lactic acid (lactate) buildup | C) Fuel depletion and central fatigue | D) ADP/Pi accumulation and reduced Ca2+ release

Total ATP depletion and lactic acid (lactate) buildup (ATP stays nearly constant, and lactate is cleared by the liver as fast as it is made)

What is maximum oxygen uptake (VO2max)?

A) The total amount of oxygen stored in myoglobin at rest | B) The oxygen consumed only during the first 6 seconds of a sprint | C) The amount of oxygen needed to clear lactic acid after exercise | D) The point at which oxygen consumption reaches a plateau and increases no further with added workload

The point at which oxygen consumption reaches a plateau and increases no further with added workload

Around what age does a person's (VO2max) typically peak?

A) Age 20 | B) Age 12 | C) Age 35 | D) Age 50

Age 20

How does the (VO2max) of an elite endurance athlete compare to a typical sedentary adult?

A) It is about the same (~35 mL/min./kg) | B) It is half as large | C) It can be twice as great (~70 mL/min./kg) | D) It is ten times greater

It can be twice as great (~70 mL/min./kg)

What is excess postexercise oxygen consumption (EPOC)?

A) The difference between elevated oxygen consumption after exercise and the normal resting rate | B) The maximum oxygen uptake reached during a sprint | C) The oxygen stored inside myoglobin at rest | D) The oxygen used by anaerobic fermentation

The difference between elevated oxygen consumption after exercise and the normal resting rate

What is the older popularized term for excess postexercise oxygen consumption (EPOC)?

A) Anaerobic threshold | B) Steady state | C) Oxygen debt | D) Central fatigue

Oxygen debt

How is the ATP generated aerobically during the early minutes of heavy postexercise breathing immediately used?

A) To produce more lactic acid | B) To regenerate creatine phosphate | C) To break down glycogen | D) To lower body temperature

To regenerate creatine phosphate

Which oxygen-storing protein in muscle fibers receives a small amount of oxygen during EPOC recovery?

A) Tropomyosin | B) Dystrophin | C) Calsequestrin | D) Myoglobin

Myoglobin

Which organ consumes extra oxygen for up to an hour after exercise to oxidize and dispose of lactate?

A) The liver | B) The kidneys | C) The pancreas | D) The spleen

The liver

How does elevated body temperature after exercise contribute to EPOC?

A) It stops ATP production | B) It breaks down myoglobin | C) It increases metabolic rate, consumes more oxygen | D) It slows down breathing rate

It increases metabolic rate, consumes more oxygen

How high can EPOC reach compared to a person's basal (resting) oxygen consumption?

A) Two times higher | B) Six times higher | C) Ten times higher | D) Half as high

Six times higher

What does a sixfold EPOC reveal about anaerobic ATP mechanisms during intense exercise?

A) They prevent any oxygen from entering muscles | B) They only work when body temperature drops | C) They generate more ATP than aerobic respiration | D) They allow six times as much physical exertion

They allow six times as much physical exertion