Build aerobic base with easy running to raise the VO2max ceiling over time

High-intensity intervals raise VO2max faster in the short term; aerobic base training raises the long-run ceiling.

Why it works

VO2max is limited by both central cardiovascular capacity (stroke volume, cardiac output) and peripheral capacity (capillary density, mitochondrial density in muscle). High-intensity work primarily targets central factors; aerobic base training (zone 2) targets peripheral factors. Athletes with the highest VO2max have extraordinary peripheral adaptation built over years of high-volume aerobic training — which cannot be compressed into intervals alone.

How to do it

1. Commit to 3–4 hours of zone 2 aerobic running per week as the majority of your training volume.
2. Do not skip easy days to add more intervals — easy running builds the infrastructure that makes intervals effective.
3. Accept that base building takes 6–24 months to show large VO2max gains.
4. Measure progress by whether your easy pace at the same HR improves over months (aerobic efficiency).

Evidence

Peripheral adaptations (capillary and mitochondrial density) are well established as contributors to VO2max and are driven by aerobic volume. The long-term VO2max ceiling is largely a function of these adaptations rather than purely cardiac output. (observational)

The contribution of central vs. peripheral factors to VO2max varies by individual training history; elite athletes are closer to their central ceiling, making peripheral gains proportionally more important.

Sources

• Holloszy & Coyle (1984), adaptations of skeletal muscle to endurance exercise, Journal of Applied Physiology

Common mistake

Replacing all easy running with intervals under the assumption that harder is always better for VO2max — which produces short-term gains but caps long-term development.