VO2max

VO2max: what is it?

Every endurance effort is ultimately limited by how much oxygen you can deliver to working muscle and how much of it those muscles can extract. VO2max puts a ceiling on that. It is measured in a lab with a mask and a gas analyser on a ramp protocol, and it is expressed relative to bodyweight so a 60 kg runner and a 90 kg rower can be compared. For a coach, the number matters less than what moves it: VO2max responds to training, drops with detraining, and improves the moment a client loses fat mass, because the denominator of the ratio shrinks.

How VO2max is measured and estimated

The reference method is a graded exercise test to exhaustion with expired-gas analysis. Load rises every one to three minutes until the client cannot continue, and VO2 is confirmed as maximal when it plateaus despite rising workload. That test needs a lab, so field coaches use estimates instead.

Every field estimate works the same way: push the client to a maximal or near-maximal effort, record something easy to measure (distance covered, final stage reached, speed at exhaustion), and feed it into a published regression equation. The estimate inherits the error of the equation and the error of the client's pacing, so treat the output as a range, not a reading.

What the number means in practice

VO2max is expressed relative to bodyweight, which has two consequences a coach should say out loud. First, a client in a fat-loss phase will see their VO2max estimate rise even in a week where their engine did not change, because the same absolute oxygen uptake is now divided by fewer kilos. Second, a heavier athlete can have a very large absolute VO2 (litres per minute) and a modest relative one; for rowing or field sports the absolute figure often matters more.

Values sit broadly between the low twenties for sedentary older adults and the high seventies or above for elite endurance athletes, and they fall with age at roughly a percent a year in untrained people. Because the published norm tables split by age and sex and disagree with each other at the edges, the honest coaching use is longitudinal: compare a client to their own previous test on the same protocol, not to a chart.

How training actually moves it

VO2max improves through two separate channels. Central adaptations increase how much oxygenated blood the heart can push per beat: bigger stroke volume, higher plasma volume, greater cardiac output. Peripheral adaptations increase how much of that oxygen the muscle can extract: more capillaries, more mitochondria, higher oxidative enzyme activity.

High-intensity intervals near maximal aerobic effort are the fastest lever on the central side, which is why 4-minute intervals and short 30/30 work appear in almost every VO2max block. Long easy work is the lever on the peripheral side and on the fatigue resistance that lets a client hold a high fraction of VO2max for an hour. A programme that only does one of the two stalls quickly.

• Untrained clients gain fastest; trained clients need targeted intensity to move the number at all.
• Detraining shows up in weeks, not months, so retest after any long break.
• Retest on the identical protocol, surface and time of day, or the comparison is noise.
• A rising VO2max estimate during a fat-loss phase is partly a bodyweight effect. Say so.

Programming around a VO2max test

Use the test to set training paces, not to give the client a score. Once you know the speed or power at which VO2max is reached, every other intensity in the plan can be written as a percentage of it, which is far more useful than an abstract ml/kg/min figure.

Schedule the test at the start of a block, after two easy days, and never in the same week as a competition or a heavy strength test. Repeat it every eight to twelve weeks. More often than that and you are measuring day-to-day noise; less often and you have no feedback loop.