VO2 max responds to training, but not all training methods raise it equally, and how much you personally improve depends partly on genetics. Here's what controlled research actually shows.
High-intensity interval training (HIIT) has produced larger average VO2max improvements than continuous moderate-intensity training in controlled research. A 2015 systematic review and meta-analysis of controlled trials in healthy adults (Milanović, Sporiš & Weston, Sports Medicine) found a pooled VO2max improvement of 4.9 mL/kg/min with HIIT, compared with 1.9 mL/kg/min with moderate-intensity continuous training (MICT) over similar training periods.
HIIT typically involves repeated bouts of near-maximal effort (roughly 85-95% of max heart rate) lasting 30 seconds to a few minutes, separated by recovery periods, repeated for multiple rounds. This higher-intensity stress appears to drive greater cardiovascular and muscular adaptations than sustained moderate effort alone — but it also carries higher injury and overtraining risk if introduced too quickly, and isn't appropriate for everyone (see the safety note on our VO2 Max Calculator page).
Re-test periodically with the Cooper run, Rockport walk, or heart rate ratio method to see whether your training is working.
Open the VO2 Max Calculator →Zone 2 training — sustained, conversational-pace aerobic exercise, roughly 60-70% of maximum heart rate — builds the aerobic base and mitochondrial capacity that underpins endurance performance. It's a legitimate and widely used component of structured training, particularly valuable for building a foundation in less-trained individuals and for accumulating training volume with lower injury risk than high-intensity work.
That said, based on the controlled-trial evidence above, moderate-intensity continuous training alone tends to produce smaller average VO2max gains than programs that include high-intensity intervals. The two approaches are best thought of as complementary — a base of aerobic volume, with some higher-intensity work layered in — rather than one replacing the other.
In the controlled trials that make up the evidence base here, training periods generally ranged from several weeks to a few months, with measurable average VO2max improvements typically reported from around 4-8 weeks of consistent structured training onward, and continued gains with sustained training over longer periods. Detraining (stopping exercise) reverses these gains over a similar timescale.
Not everyone improves their VO2max by the same amount from identical training. The landmark HERITAGE Family Study (Bouchard et al., Journal of Applied Physiology, 1999) put 481 previously sedentary adults through an identical, supervised 20-week endurance training program. The average VO2max gain was substantial, but individual responses varied enormously — some participants showed little to no measurable improvement, while others gained more than double the average. Statistical modelling attributed a meaningful portion of this variation (an estimated maximal heritability around 47%) to genetic factors, and the tendency to respond well or poorly to training also ran in families.
Breathing exercises and respiratory muscle training are sometimes marketed as a way to raise VO2max. The honest picture: respiratory muscle training has shown some benefit for respiratory muscle endurance and perceived breathlessness during exercise in various studies, but it has not been established as a reliable, direct method of raising VO2max itself in the way that aerobic exercise training has. We're not aware of strong, consistent controlled-trial evidence supporting breathing exercises as a standalone method for meaningfully increasing VO2max, and we won't claim otherwise. If you see strong claims to the contrary, treat them with appropriate scepticism until you can trace them to a specific, credible controlled study.
General information only — not an individualised training prescription. Based on the research summarised above, common evidence-based approaches to improving VO2max tend to share a few features:
VO2max responds to training, and controlled research consistently shows high-intensity interval training producing larger average gains than steady-state training alone, with aerobic base work as a complementary foundation. Expect measurable change over weeks to months, and remember that genetics meaningfully affects how much any individual improves — a smaller result than a friend's isn't necessarily a sign you're doing something wrong.
What is the best way to improve VO2 max?
High-intensity interval training (HIIT) has shown larger average VO2max improvements than steady-state continuous training in controlled trials — a 2015 meta-analysis found a pooled improvement of 4.9 mL/kg/min with HIIT versus 1.9 mL/kg/min with moderate-intensity continuous training. A well-rounded program combining both, done consistently, tends to work better than either alone.
How long does it take to improve VO2 max?
Measurable VO2max improvements are typically reported after 4-8 weeks of consistent structured training in exercise-science studies, with continued gains over months. Individual results vary substantially — some people respond quickly, others very little, for reasons that are only partly understood.
Does zone 2 training improve VO2 max?
Zone 2 (moderate-intensity aerobic) training builds the aerobic base and mitochondrial capacity that supports VO2max, and contributes to improvement, particularly in less-trained individuals. However, controlled trials generally show high-intensity interval training produces larger average VO2max gains than moderate-intensity continuous training alone — the two are complementary rather than interchangeable.
Can breathing exercises increase VO2 max?
The evidence here is limited. Breathing exercises may improve respiratory muscle endurance and perceived breathlessness in some contexts, but they have not been established as a reliable way to directly raise VO2max the way aerobic exercise training has. Treat claims about breathing exercises substantially raising VO2max with caution until stronger evidence exists.