How to increase your VO₂ max.

VO₂ max is limited by oxygen delivery (cardiac output, hemoglobin) far more than by oxygen extraction at the muscle. That's why interval work targeting stroke volume — hard efforts long enough that the heart chamber fills fully — moves the number faster than low-intensity volume alone.

The trial evidence converges on three ingredients: (1) short bouts near VO₂ max, (2) a large weekly volume of easy aerobic work, and (3) strength training to preserve the muscle mass and stroke volume that VO₂ max depends on.

The most-studied VO₂-max intervention. Helgerud et al. (2007) had untrained subjects perform 4 × 4-minute intervals at 90–95% max heart rate, with 3-minute active recoveries, three times per week. After 8 weeks, VO₂ max rose 10.0% — roughly twice the gain of matched-work continuous running.

• 10-minute easy warm-up.
• 4 minutes hard (RPE 9/10, cannot speak in full sentences).
• 3 minutes easy jog. Repeat 4 times.
• 5-minute cool-down.

Once a week is the sustainable dose for most people; twice a week is the ceiling. More is not better — the stimulus depends on hitting the target intensity, and stacked sessions blunt it.

Zone-2 (conversational pace, roughly 60–70% max HR) grows the mitochondrial density and capillary bed your intervals draw against. Two to three sessions of 45–60 minutes per week is the minimum effective dose. Elite endurance athletes do 80% of their training here for a reason — it's the substrate that lets the hard sessions produce adaptation instead of just fatigue.

After 40, sarcopenia (age-related muscle loss) and reduced left- ventricular compliance both cap the ceiling of VO₂ max. Two full-body sessions per week — squat or leg press, hip hinge, horizontal push, horizontal pull, loaded carry — protect both. Heavy sets (5–8 reps) do more here than high-rep endurance work.

A metabolic cart is the reference standard. Without one, three proxies track direction reliably:

• Cooper 12-minute run. Distance covered on a track in 12 minutes. Estimated VO₂ max = (distance in metres − 504.9) / 44.73.
• 1.5-mile time trial. Well-validated against lab VO₂ max; easy to repeat monthly.
• Wrist-based estimates (Garmin, Apple Watch, Polar). Absolute values drift 5–15%, but the trend line is usable. That's what AeroGlyphics' SLAM forecast engine is built for — extracting signal from noisy wearable readings and projecting the trajectory forward.

Skip: fasted intervals, "zone-5-only" training blocks, supplement stacks marketed as VO₂-max boosters (no oral supplement has reliably moved lab-measured VO₂ max in an RCT), and altitude tents without a coach. The dose–response curve is boring and well-mapped; deviations mostly cost time.