VO2 max, lactate threshold, and aerobic capacity

What VO2 max actually measures

VO2 max is the maximum rate of oxygen the body can use during exercise. Measured in ml/kg/min. It's the gold-standard test of aerobic capacity.

A sedentary 30-year-old male might score 35 ml/kg/min. A trained recreational runner might score 50. Elite endurance athletes hit 70-85. World-class cross-country skiers have hit 95+.

VO2 max is partly genetic (~50%) and partly trainable (~50%). The trainable portion comes from:

Cardiac output (heart pumps more blood per beat)
Capillary density (blood reaches muscles faster)
Mitochondrial density (cells use oxygen more efficiently)
Lung diffusion capacity (oxygen transfers faster from air to blood)

How to train VO2 max

The classic protocol: 4×4 minute intervals at 90-95% max HR with 3-minute recoveries. 2-3 sessions per week, 6-8 weeks.

Other valid options:

8-10×30-second sprints with 1:1 rest
Hill repeats
Tabata-style 20:10 protocols

The training must be hard enough to spend significant time near VO2 max. Easy cardio doesn't move VO2 max much — it builds an aerobic base.

Lactate threshold

VO2 max is the ceiling. Lactate threshold is the speed/intensity at which lactate begins accumulating faster than the body can clear it.

For endurance athletes, lactate threshold matters more than VO2 max because most racing happens below VO2 max but near or at threshold.

Estimated thresholds:

Untrained: ~50% of VO2 max
Trained: 75-90% of VO2 max

This means two athletes with identical VO2 max can perform very differently if their thresholds are different.

Training lactate threshold

Tempo work: 20-40 minute efforts at "comfortably hard" — the pace you could hold for ~1 hour. Trains the body to clear lactate efficiently.

For general-pop clients

Most clients don't need maximal VO2 max testing. Use perceived exertion or HR zones:

Zone 2 (easy, can hold a conversation) — 70-80% of weekly cardio volume
Zone 4-5 (hard, can't talk) — 20-30% of weekly cardio volume, in interval form

This 80/20 split is what elite endurance athletes do — and it works for general fitness too.

TL;DR

VO2 max = maximum oxygen utilization rate. Lactate threshold = intensity where lactate accumulates. Both are trainable. Most clients improve fastest with 80% easy + 20% hard intervals — not constant moderate effort.