Exercise intensity is how hard you work, from an easy effort you can keep up for a long time to short efforts close to your limit. Interval training alternates harder efforts with easier periods.
A review found that it can be an effective alternative to traditional endurance training,
producing similar or greater physiological changes when the total work is matched (PMID 22289907).
Short interval sessions can save time. The same review reports that low-volume interval training can produce physiological changes comparable to moderate continuous training,
with a much smaller time commitment (PMID 22289907). Lack of time is the most commonly cited barrier to regular exercise (PMID 22289907).
Both approaches raise aerobic fitness. A meta-analysis of 28 controlled studies in healthy adults aged 18 to 45 found large VO2max gains after endurance training and after interval
training, and somewhat greater gains after intervals (PMID 26243014).
Steps
1. **Choose intervals when time is short.** Low-volume interval training needed much less time for comparable changes (PMID 22289907).
2. **Keep some steady sessions too.** Endurance training also gave large VO2max gains (PMID 26243014).
3. **Give a programme several weeks.** Longer programmes tended to give larger gains (PMID 26243014).
Duration
The meta-analysis included programmes of two weeks or longer, and longer programmes tended to give larger gains (PMID 26243014).
Low-volume interval programmes use less total exercise time than moderate continuous training (PMID 22289907).
Limitations
- **Low-volume interval training is less well studied** than traditional endurance training, the review notes (PMID 22289907).
- **The review is narrative**, so it summarises studies rather than pooling their results (PMID 22289907).
- **The meta-analysis covered healthy adults aged 18 to 45** (PMID 26243014).
- **This guide has not been reviewed by a clinician.** `reviewStatus` above says so.
Cautions
- **Build up intensity gradually**, especially if you are new to exercise.
- **If you have a long-term health condition or take regular medicines, check with a clinician before starting hard intervals.**
Related canonical ingredients
No ingredient is linked from this guide. It covers how hard to exercise, and it does not point to a product.
Sources
| PMID | Title |
| --- | --- |
| 22289907 | "Physiological adaptations to low-volume, high-intensity interval training in health and disease" |
| 26243014 | "Effectiveness of High-Intensity Interval Training (HIT) and Continuous Endurance Training for VO2max Improvements: A Systematic Review and Meta-Analysis of Controlled Trials" |