Research · 3 min read · 2026-10-15
Intervals or steady running?
Both gave large gains in maximal oxygen uptake across 28 studies. Intervals gave a little more.
Do you need intervals to get fitter, or is steady running enough? A meta-analysis of 28 studies compared the two.
What the researchers did
Researchers pooled controlled studies of healthy adults aged 18 to 45 who trained for at least two weeks, either with high-intensity intervals or with steady endurance training. In total, 723 people took part. Maximal oxygen uptake was measured before and after.
What they found
Both types of training gave large improvements compared with not training: 4.9 ml/kg/min with steady training and 5.5 ml/kg/min with intervals.
Intervals gave a slightly larger improvement than steady training, about 1.2 ml/kg/min more. People who started with lower fitness and programmes that lasted longer tended to improve more with both types.
What it means for you
Both work. Steady running builds a lot of fitness on its own, and intervals add a little more. For most runners, the best answer is both: mostly easy running, with some interval sessions.
Intervals are hard, and more of them is not always better. They work best when you are fresh enough to do them well.
What the study can't tell you
The studies measured maximal oxygen uptake, not race times. Most participants were young and not very fit when they started, and the studies were short. Trained runners usually improve less.
How we use it
PX7 Training combines easy running with harder sessions such as intervals and tempo runs. How many hard sessions you get depends on your goal, the time you have and how you recover.
Source
- Milanović, Sporiš & Weston (2015), Effectiveness of high-intensity interval training (HIT) and continuous endurance training for VO2max improvements: a systematic review and meta-analysis of controlled trials. Sports Medicine.
Written by Jørgen Larsen for PX7 Training.