New Super Intervals from Norway (#238)

Norway has contributed a lot to the world: A-ha, Kygo, cod, cheese slicers, Petter Northug, and the Ingebrigtsen brothers – not to mention fascinating sports research, especially regarding endurance training. In the past decade, there has been a significant emphasis on high-intensity training. The classic 4x4 minutes gained considerable attention with promising results for VO2max. Then, studies indicated that 4x8 minutes, and even shorter intervals, could be just as effective or even better.

In cycling, short high-intensity intervals like 60/30, 40/20, and 30/15 have been popular for quite a while. Research suggests they're effective in boosting VO2max and enhancing cycling-specific Time Trial performance – in other words, maintaining a steady effort over a prolonged period and then going all-out at the finish. This was demonstrated in a Norwegian study that compared 30/15 intervals with 4x5-min intervals among trained cyclists.

The same research team, headed by Bent R Rønnestad, recently published a new study. The setup is similar, but this time involving elite-trained cyclists. The better trained you are, the more stimulus – both in intensity and volume – seems necessary for the body to sustain and improve performance. Let's take a closer look at this study now.

The study aimed to compare the effects of 3 weeks of high-intensity training (consisting of 9 HIT sessions) among 18 elite cyclists (VO2max 73 ± 4 ml/kg/min). One group, SI (short-intervals), completed 3 sets of 30/15 intervals (totaling 9.5 minutes of interval time per session) with a 3-minute rest between sets. The other group, LI (long-intervals), did 4 sets of 5-minute intervals with a 2.5-minute rest. Overall, SI completed 19.5 minutes and LI completed 20 minutes of interval time, along with 15 and 7.5 minutes of rest at 50% of the interval intensity, respectively.

The figure below indicates that RPE (perceived exertion) was similar, even though the average power was significantly higher in the SI group (73 watts / 16.5% higher).

They measured VO2 max, cycling economy, efficiency, and power at VO2 max at 4 mmol lactate, as well as a 20-minute Time Trial (TT) test. The cyclists were divided into two homogeneous groups, matched as closely as possible in VO2 max, height, weight, and age. Leading up to the testing period, they trained with high volume (17 hours) and low intensity, then switched to high intensity and halved weekly volume (9 hours) for the testing period.

Previous research has often involved untrained or moderately trained subjects where short intervals showed good results, although longer intervals also led to improvements. The question was whether the results would differ for elite cyclists.

After 3 weeks of interval training, no significant percentage change in VO2max was observed between the groups, although SI showed a slight increase while LI stayed the same. However, SI improved their Wmax — the power maintained at VO2max — by +3.7 ± 4.3% (about 10 watts), whereas Wmax in the LI group remained unchanged (−0.3 ± 2.8%).

No changes in movement economy were detected, which was expected as all participants were experienced elite cyclists and the test period was brief (3 weeks). When measuring power at 4 mmol lactate, SI improved, while LI slightly declined. The results become even more intriguing in the 20 min TT test: SI enhanced their anaerobic capacity and increased their power, while LI actually worsened. Exact numbers can be found here.

SI boosted their average power by 4.7 ± 4.4% compared to LI, which either remained unchanged or dropped by −1.4 ± 2.2%. The average power for SI was 343 watts before the test period and increased to 358 watts after, marking an improvement of 15 watts in just 3 weeks. This clearly demonstrates an improvement in threshold watts over a relatively short period.

In summary, the results suggest that short intervals led to greater improvements in the measured parameters than longer intervals, where the results were unchanged or even worse for elite cyclists.

Conclusions & Reflections

It's not entirely unexpected that VO2max didn't change significantly, as seen in previous studies on well-trained cyclists, but it is somewhat surprising that the SI group's VO2max didn't improve more. However, a 16-watt increase in Wmax over 3 weeks is a commendable outcome. The time frame, number of interval sessions, and the participants being elite cyclists likely contributed to the limited VO2max increase. It’s important to note that three interval sessions per week isn’t substantial; there have been studies involving elite athletes with more frequent interval sessions showing increased VO2max. As mentioned, the better trained you are, the more stimuli you need to achieve further adaptation.

The highest VO2max doesn't win all the races. What's more intriguing here are the enhancements in performance factors during the 20-minute test. The SI group managed to sustain a higher average power output and higher lactate levels than before the interval period, indicating improved ability to perform at higher lactate thresholds. A possible explanation is the higher average power SI maintained compared to LI: 94% versus 79% of pre-Wmax.

Before drawing any major conclusions, it's important to remember that the test group was small, the testing period was brief, and the participants reduced their overall training volume during this period. However, the takeaway should still be that short intervals appear effective for both untrained and well-trained individuals, leading to improvements in cycling performance.

Over time, it's likely best to mix short and long intervals to expose your body to various stimuli. Observing the performance increase in your ability to produce watts and tolerate lactate, this should be an excellent program to get race-ready and fine-tune your form—perhaps something to try for your race debut!

As always: you get good at what you train!

You can find the full study here:

https://onlinelibrary.wiley.com/doi/full/10.1111/sms.13627