This video introduces an innovative cycling workout called 30/15 micro-intervals and explains why it can be more effective than traditional long intervals while even feeling easier mentally. Based on research by world-class sports scientist Professor Bent Ronnestad, it emphasizes the importance of time spent above 90% of VO2 max and explains how 30/15 micro-intervals maximize that time. The video includes a real training attempt, data comparison, and scientific evidence showing why this session works so well.

1. Understanding Interval Training and the Importance of VO2 Max

Before introducing the session, the video clearly explains what interval training is. Interval training alternates hard riding periods with easy recovery periods and is a highly effective way to achieve specific performance goals or improve overall health and fitness.

"Interval training is alternating hard riding sections with easy recovery sections."

For high-intensity training, the video stresses that there is a direct correlation between time spent above 90% of VO2 max and training response. In other words, the more time you spend above 90% of VO2 max, the fitter you get. This is already a well-established fact, and Professor Bent Ronnestad has supported it through many studies. The problem is that 90% of VO2 max is extremely hard. This is where the "magical" workout appears.

2. The Arrival and Effect of 30/15 Micro-Intervals

The magical workout is 30/15 micro-intervals. In this format, you pedal very hard for 30 seconds, then recover for 15 seconds, and repeat. It works almost like a shortcut for spending as much time as possible above 90% of VO2 max. The video jokes that it is called a magic bullet or even the goose that lays golden eggs.

The host recently learned the session from his coach while training for the Seven gravel race and says it had a major effect. The coach told him to do three or four sets of 13 repetitions of 30/15 intervals. At first, it felt complicated and strange.

"Honestly, when Simon explained it, I thought it sounded weird. Who repeats something 13 times?"

But after doing the workout himself, he says he was genuinely shocked by the effect.

3. Road Test: 30/15 Micro-Intervals vs. 5-Minute Intervals

The host directly compares 30/15 micro-intervals with traditional 5-minute intervals in a road test.

3.1. Experiencing 30/15 Micro-Intervals

He performs 30/15 intervals by riding at 500W for 30 seconds and 200W for 15 seconds. Early in the session his legs feel stiff, but the short recovery periods make it possible to finish.

"You never have to go hard for that long. You can make it to the end." "Fifteen seconds goes by really fast." "The recovery section on a steep hill is rough."

Physically, the session is hard, but mentally it feels much less difficult. Because each interval is short, you can endure it by thinking, "It will be over soon anyway."

3.2. Experiencing 5-Minute Intervals

Next, the host attempts 5-minute intervals at a steady 430W. Unlike the 30/15 session, the 5-minute interval feels mentally heavy from the start.

"I think it is mentally harder, because you know you have to keep holding the power." "Nothing makes life feel as long as this interval workout."

In the end, the 5-minute interval feels much harder psychologically than the 30/15 session.

4. Checking the Training Effect Through Data

The host compares the data from the two sessions.

• 30/15 intervals: Over 9 minutes and 30 seconds, he averaged 418W and spent 6 minutes and 30 seconds above 450W. It took a little longer to reach 90% of VO2 max, but he stayed in that zone for more than 7 minutes.
• 5-minute intervals: He averaged 436W and reached 90% VO2 max sooner, but stayed there for only 4 minutes.

Converted to the full session, the 30/15 workout produced 22 minutes and 30 seconds above 90% of VO2 max, while the 5-minute interval workout produced only 16 minutes.

Research shows the same pattern. According to Professor Ronnestad's study, after 10 weeks, the group performing 30/15 intervals increased power in a 40-minute time trial by 12%, while the long-interval group improved by only 4%. In a 5-minute test, the 30/15 group improved by 8%, while the long-interval group did not improve at all. In a study of elite cyclists, the 30/15 group improved threshold power by 3% in just three weeks, while the long-interval group actually decreased by 3.5%. The 30/15 group also improved lactate tolerance, which is an impressive result.

5. A Deep Interview with Professor Bent Ronnestad

The host interviews Professor Bent Ronnestad, who first developed 30/15 micro-intervals, to understand the scientific background and practical application of the workout.

5.1. How 30/15 Intervals Were Created

Professor Ronnestad began researching interval-training optimization around 2010. At the time, short interval training usually meant 30 seconds of maximal effort followed by 3-4 minutes of rest, which he did not consider a fair comparison with traditional 5- or 6-minute long intervals.

He drew inspiration from research by Bengt Saltin, a famous exercise physiologist from the 1960s. Saltin's work suggested that a 2:1 ratio between work and recovery time was especially effective for high-intensity VO2 max time and distance covered. Ronnestad was also fascinated by Veronique Billat's 1990s research on time spent at VO2 max or above 90% of VO2 max. With this background, he designed 30-second work and 15-second recovery intervals for cyclists and began comparing them with 3-minute and 5-minute intervals.

In early studies, all intervals used the same power output, maximum aerobic power. The 30/15 group lasted almost twice as long before fatigue and spent far more time above 90% of VO2 max. Later, he ran fairer comparisons that adjusted power output depending on interval type, and again proved that 30/15 intervals produced a better training response than 5-minute intervals.

5.2. Broad Training Effects and Improved Lactate Tolerance

Professor Ronnestad explains that 30/15 intervals improve not only VO2 max, but also many other performance areas. Benefits were seen in 30-second maximal sprints, 5-minute maximal efforts, 40-minute maximal power, and 4 mmol lactate-threshold power. It is especially surprising that 30/15 intervals also improved long sustained efforts such as 40-minute power.

A later study of elite cyclists found that the 30/15 group had higher lactate tolerance. This matched how participants felt during training: they sensed that they had become better at tolerating lactate.

5.3. Why Micro-Intervals Are Effective

Professor Ronnestad says the biggest reason micro-intervals work is that they allow athletes to spend more time above 90% of VO2 max. In a recent study measuring oxygen uptake directly across more than 500 interval sessions, the people who reached the highest percentage of VO2 max over the full period showed the greatest improvements in endurance-related variables.

"I think time above 90% of VO2 max, or time at a high VO2 max, is very important for adaptation because it measures the real stress placed on the body."

5.4. Applying 30/15 Intervals to Real Training Plans

The professor says that although research is conducted in controlled environments, these sessions can be included in real training plans. Studies showed benefits in mixed training environments where 30/15 intervals were integrated with other threshold training and low-intensity training.

However, he does not recommend training with all-out maximal effort exactly as in research. Instead, he offers practical advice:

"In my experience, the rule is to produce roughly the power you could hold for five minutes during the 30-second work period, then reduce that power by half during the 15-second recovery before starting again."

He adds that the exact numbers should be adjusted for individual characteristics.

5.5. Why Long Intervals Still Matter

Professor Ronnestad emphasizes that even though 30/15 micro-intervals are effective, that does not mean long intervals are unnecessary.

"It is not either-or. I think you should include both."

Holding steady power for a long time is psychologically difficult, but it remains important in certain race situations, such as time trials. To improve the effect of long intervals, he suggests a fast start method. For example, in a 5-minute interval, ride at higher power for the first 2 minutes and then lower the power for the remaining 3 minutes. This can increase time above 90% of VO2 max. Heart-rate-based training can naturally create a similar fast-start effect.

5.6. Is It a Magical Training Session?

In the end, Professor Ronnestad says 30/15 micro-intervals are not a magical workout, but they are a very effective tool to include in a training plan. They are especially useful for riders who find rapid power changes at short intervals fun and mentally easier than traditional methods.

"If you are actually doing intervals and you think short intervals are more fun than the traditional method, just keep doing them."

No matter how effective a workout is, it does not matter if you never do it. The important thing is to find training you can enjoy and keep doing consistently. He also adds that similar micro-interval ratios such as 30/15 and 40/20 are probably not very different; what matters more is the overall structure and consistency of the training.

6. Closing Thoughts

Through the interview with Professor Bent Ronnestad, the host becomes convinced of the scientific basis and practical value of 30/15 micro-intervals. He says that whatever your cycling goal is, whether peak performance or general health and fitness, doing at least some VO2 max training will bring clear benefits.

"Whatever your cycling goal is, whether top performance or general health and fitness, doing even a little VO2 max training will definitely bring major benefits."

30/15 micro-intervals are physically demanding but can feel mentally easier, while also providing a scientifically validated training effect. If you want to change your training routine or improve efficiently, this workout is worth trying.