VO2 max describes what?

The maximum rate at which the body can take up and use oxygen during hard effort

The total volume of air the lungs hold at rest

The number of breaths taken per minute at rest

The oxygen content of arterial blood

Lactate produced during hard exercise is best described as what?

A fuel that the heart and other muscles take up and use

A waste product responsible for soreness two days later

A hormone released by the liver

A protein that repairs damaged fibres

Delayed onset muscle soreness usually peaks how long after unfamiliar exercise?

Immediately, then fading within an hour

A motor unit consists of what?

One motor neuron together with all the muscle fibres it controls

A single muscle fibre on its own

A muscle and its opposing muscle

A joint together with its ligaments

In an eccentric contraction, the muscle does what?

Produces force while lengthening

Produces force while shortening

During sustained aerobic exercise, heart rate rises mainly in order to do what?

Deliver more oxygenated blood to the working muscles

Increase the total volume of the lungs

Which change is typical in muscle tissue after a sustained period of endurance work?

More mitochondria and a denser network of capillaries

Fewer blood vessels reaching the fibres

A permanent rise in resting heart rate

Complete loss of fast-twitch fibres

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Health & Fitness Medium ⚡ 10 Questions ⏱️ ~7 Mins +100 XP

Muscles, Oxygen and Effort

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General exercise physiology: how muscle is powered, why it tires and what changes in it over months of use.

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About this topic

Exercise physiology is unusually good at overturning things people are confident about. Lactate was blamed for next-day soreness for most of a century and turns out to be a fuel that other tissues take up and burn. The limit on how much oxygen a healthy person can use during hard work is usually the heart rather than the lungs. Muscle soreness after unfamiliar effort tracks lengthening contractions more than exertion as such. What follows is descriptive physiology rather than guidance. It covers how a contraction is powered, how force is graded, and the changes that show up in muscle tissue after sustained endurance work — the mechanics that any specific training or health decision would sit on top of, not the decision itself.

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Muscles, Oxygen and Effort: all 10 questions and answers

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1Skeletal muscle fibres are conventionally divided into which two broad types?
- A Red blood and white blood
- B Slow-twitch and fast-twitch Correct
- C Smooth and cardiac
- D Voluntary and cardiac
Answer: B. Slow-twitch and fast-twitch

Why: Slow fibres are dense with mitochondria and resist fatigue, while fast fibres generate force quickly and tire sooner. Almost every muscle contains a mixture of both.
2VO2 max describes what?
- A The maximum rate at which the body can take up and use oxygen during hard effort Correct
- B The total volume of air the lungs hold at rest
- C The number of breaths taken per minute at rest
- D The oxygen content of arterial blood
Answer: A. The maximum rate at which the body can take up and use oxygen during hard effort

Why: In healthy people the ceiling is usually how much blood the heart can pump, not how much air the lungs can move. That is why cardiac output is treated as the limiting step.
3Which molecule is the immediate energy currency spent by a muscle contraction?
- A Insulin
- B Haemoglobin
- C Collagen
- D ATP Correct
Answer: D. ATP

Why: Muscle stores only a few seconds' worth at a time. It is continually resynthesised, first from creatine phosphate and then from glucose and fat.
4Lactate produced during hard exercise is best described as what?
- A A hormone released by the liver
- B A protein that repairs damaged fibres
- C A fuel that the heart and other muscles take up and use Correct
- D A waste product responsible for soreness two days later
Answer: C. A fuel that the heart and other muscles take up and use

Why: The old link between lactic acid and next-day soreness has not survived testing. Blood lactate returns toward resting levels within about an hour of stopping.
5Delayed onset muscle soreness usually peaks how long after unfamiliar exercise?
- A Immediately, then fading within an hour
- B One to two days afterwards Correct
- C Within ten minutes
- D About a week afterwards
Answer: B. One to two days afterwards

Why: It is associated with microscopic damage from lengthening contractions. That is why walking downhill tends to produce more of it than walking uphill.
6A motor unit consists of what?
- A One motor neuron together with all the muscle fibres it controls Correct
- B A single muscle fibre on its own
- C A muscle and its opposing muscle
- D A joint together with its ligaments
Answer: A. One motor neuron together with all the muscle fibres it controls

Why: Units serving the eye or the fingers contain only a handful of fibres, which allows fine control. Units in the thigh may contain several hundred.
7In an eccentric contraction, the muscle does what?
- A Produces force while shortening
- B Produces no force at all
- C Contracts with no nerve signal
- D Produces force while lengthening Correct
Answer: D. Produces force while lengthening

Why: Lowering a load under control is the everyday example. Muscle can resist more weight this way than it can lift while shortening.
8Tendons and ligaments differ in that a tendon connects what?
- A One muscle to another
- B Skin to underlying muscle
- C Muscle to bone Correct
- D One bone to another
Answer: C. Muscle to bone

Why: Both are dense collagen structures. Neither has anything like the blood supply of muscle, which is part of why they adapt and repair more slowly.
9During sustained aerobic exercise, heart rate rises mainly in order to do what?
- A Convert fat into glucose
- B Deliver more oxygenated blood to the working muscles Correct
- C Cool the blood directly
- D Increase the total volume of the lungs
Answer: B. Deliver more oxygenated blood to the working muscles

Why: Stroke volume, the amount pumped per beat, also increases early in the effort. Endurance-trained people often show notably low resting rates as a consequence of that adaptation.
10Which change is typical in muscle tissue after a sustained period of endurance work?
- A More mitochondria and a denser network of capillaries Correct
- B Fewer blood vessels reaching the fibres
- C A permanent rise in resting heart rate
- D Complete loss of fast-twitch fibres
Answer: A. More mitochondria and a denser network of capillaries

Why: These changes improve how much oxygen is extracted and used at the muscle itself. They are separate from any change in how much blood the heart can pump.

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