Question 1

What is VO2 max and can you improve it?

Accepted Answer

**VO2 max** is the maximum rate at which your body can take in, transport and use oxygen during intense exercise, expressed in millilitres of oxygen per kilogram of body weight per minute (ml/kg/min). It is the standard measure of aerobic capacity.

**Why it matters.** Aerobic energy production requires oxygen, so the rate at which you can deliver and use it sets a ceiling on sustained effort. It is also one of the stronger predictors of **all-cause mortality** in the research literature — stronger than many conventional risk factors — which is why it attracts interest beyond sport.

**What limits it.** In most people the constraint is **central**: the heart's ability to pump oxygenated blood, primarily **stroke volume**. Peripheral factors — capillary density, mitochondrial content, haemoglobin — contribute, but cardiac output is generally the bottleneck.

**Typical values:** untrained adults commonly sit around 30–40 ml/kg/min, recreationally trained people 45–55, and elite endurance athletes above 70, with the highest recorded values in cross-country skiers and cyclists exceeding 85.

**Can you improve it?** Yes, substantially — with limits.

**Untrained people can typically improve 15–20%** or more within a few months of consistent training. Gains are largest from the lowest starting point.

**Trained people improve far less**, and highly trained athletes may be close to their ceiling, at which point performance improves through **efficiency and lactate threshold** rather than VO2 max.

**Genetics sets the range.** Heritability estimates for baseline VO2 max and for **trainability** are both substantial. Some people respond strongly to identical training and others barely — a well-documented phenomenon, and not a matter of effort.

**What training works.** Both high-intensity intervals near maximal effort and high volumes of lower-intensity work raise it; most endurance programmes combine them, with the majority of time at low intensity.

**Age reduces it** roughly 1% a year from the thirties, though training substantially slows the decline.

**Watch estimates** from smartwatches are approximations, useful for tracking trends rather than absolute accuracy.

Question 2

How quickly do you lose fitness if you stop training?

Accepted Answer

Detraining happens faster than most people fear for strength and slower than feared for skill — and the different systems decline at very different rates. Cardiovascular fitness declines fastest.

Question 3

Why does cardio get easier the fitter you get?

Accepted Answer

Because a substantial amount of your physiology genuinely rebuilds itself in response to repeated endurance work. The same run at the same pace demands less of you because the machinery delivering

Question 4

How much exercise do you actually need for health?

Accepted Answer

The major guidelines converge closely, and the figures are lower than many people assume — while the biggest benefit comes from a step most people overlook. The UK Chief Medical Officers' and WHO

Question 5

What is zone 2 training, and why has it become so popular?

Accepted Answer

Training at a low, sustainable intensity — roughly the top of the range where you can hold a conversation — for long durations. It has become fashionable recently, but it is not new: it is what

Question 6

What is the difference between aerobic and anaerobic exercise?

Accepted Answer

The distinction is which energy system dominates, and that depends on intensity and duration rather than on the activity itself. Aerobic means "with oxygen". At moderate intensity, your body meets

Question 7

What is the difference between training for strength, size and endurance?

Accepted Answer

They are different adaptations produced by different training variables, and the same exercises can serve any of them depending on how they are programmed. Strength — producing maximal force. Typical

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