VO2max is the highest rate at which the body can take up and use oxygen during hard exercise. Laboratory tests measure it directly,
and one US registry set reference values from 22,379 tests in apparently healthy adults aged 20 to 89 (PMID 34809986). In that registry, median values were lower at older ages,
higher in men, and higher on a treadmill than on a bike (PMID 34809986).
Aerobic capacity falls with age, and the fall speeds up. In 810 healthy adults followed for a median of 7.9 years,
peak oxygen uptake fell in every decade from the 20s to the 70s (PMID 16043637). The fall was 3 to 6 percent per decade in the 20s and 30s,
and more than 20 percent per decade from the 70s (PMID 16043637).
Training raises it. A meta-analysis of 28 controlled studies in healthy adults aged 18 to 45 found large VO2max gains from both endurance and interval training,
and somewhat greater gains after intervals (PMID 26243014). In one trial, 40 moderately trained men raised VO2max more with four 4-minute intervals than with steadier running of
the same total work (PMID 17414804).
Hard work is usually a small share of training. Descriptive studies of competitive endurance athletes converge on about 80 percent of sessions at low intensity and about 20 percent
dominated by high-intensity work (PMID 20861519).
Steps
1. **Build a base of regular aerobic training.** Both endurance training and interval training raised VO2max in the meta-analysis (PMID 26243014).
2. **Add one interval format.** The 4 x 4 format is four 4-minute efforts at 90 to 95 percent of maximal heart rate, with 3 minutes of easier work between them (PMID 17414804).
3. **Keep most sessions easy.** About four in five sessions were low intensity in the athlete studies (PMID 20861519).
4. **Give a programme time.** Longer programmes tended to give larger gains in the meta-analysis (PMID 26243014).
5. **Compare a test result only with values for the same kind of test.** Reference values differed between treadmill and bike tests (PMID 34809986).
Duration
The interval trial ran three sessions a week for eight weeks (PMID 17414804). The meta-analysis included programmes of two weeks or longer,
and longer programmes tended to give larger gains (PMID 26243014). The age-related fall in peak oxygen uptake was measured over a median of 7.9 years (PMID 16043637).
Limitations
- **The meta-analysis covered healthy adults aged 18 to 45**, so it says less about older adults (PMID 26243014).
- **The 4 x 4 trial studied 40 moderately trained men**, so the size of the effect may differ in women, older adults and beginners (PMID 17414804).
- **The ageing data come from one long-running study of healthy adults**, and the rate of decline was similar across levels of self-reported leisure activity (PMID 16043637).
- **The reference values come from US laboratories** and describe groups, so they are not personal targets (PMID 34809986).
- **This guide has not been reviewed by a clinician.** `reviewStatus` above says so.
Cautions
- **If you have a long-term health condition or take regular medicines, check with a clinician before starting interval training.**
- **Build up gradually.** Add intervals only after weeks of regular easier training, and keep most sessions easy (PMID 20861519).
Related canonical ingredients
No ingredient is linked from this guide. It covers aerobic fitness and how training changes it, and it does not point to a product.
Sources
| PMID | Title |
| --- | --- |
| 34809986 | "Updated Reference Standards for Cardiorespiratory Fitness Measured with Cardiopulmonary Exercise Testing: Data from the Fitness Registry and the Importance of Exercise National Database (FRIEND)" |
| 16043637 | "Accelerated longitudinal decline of aerobic capacity in healthy older adults" |
| 26243014 | "Effectiveness of High-Intensity Interval Training (HIT) and Continuous Endurance Training for VO2max Improvements: A Systematic Review and Meta-Analysis of Controlled Trials" |
| 17414804 | "Aerobic high-intensity intervals improve VO2max more than moderate training" |
| 20861519 | "What is best practice for training intensity and duration distribution in endurance athletes?" |