Great news for runners: Improve performance while easing up on sprints

A group of runners jogs leisurely along a park's trails. Thirty seconds later, they accelerate to a moderate pace for 20 seconds before blasting into a ten-second sprint. 10-20-30 interval running training is a widespread training concept because it is effective at improving running times and fitness levels, even with marked reduction in the amount of training.

Now, new research from the University of Copenhagen’s Department of Nutrition, Exercise and Sports (NEXS) demonstrates that you do not necessarily need to give it all you’ve got in the final ten-second sprint to get into good shape and improve your times.

In the study, 19 runners replaced their normal training with 10-20-30 workouts for six weeks. The results came as a surprise:  Half of the group, whom the researchers had instructed to perform at only 80 percent during the final ten-second sprint, achieved as much progress in their running performance and fitness as the group that sprinted at 100 percent.

"The result of the study really came as a surprise. We think that it is related to the fact that training at 80 percent of one’s maximum still gets the heart rate up significantly higher than a runner’s typical training. A higher heart rate leads to improvements in heart function and circulation, as evidenced in their times and fitness levels," says Professor Jens Bangsbo of the Department of Nutrition, Exercise and Sports, who headed the study.    

Sprint 100 percent to achieve the maximum benefit

Over the five-kilometer distance that the researchers tested the 19 runners on, the "slow" group – who sprinted at only 80 percent of their max – achieved an average improvement in their running time of 42 seconds compared to their original time prior to the six-week interval training. Meanwhile, runners in the "fast" group only shaved an average of 24 seconds off of their times. Both groups of runners improved their overall fitness (maximum oxygen uptake) by seven percent.

At first glance, it appears as if holding back somewhat on one’s final sprint carries nothing but advantages. However, as the researchers dug deeper to better understand how the runners' muscles reacted to the two loads, one important difference emerged.

"Only the max group formed more mitochondria, which are the tiny power plants within our cells. They are important for muscular endurance and the ability of our muscles to engage in long-term work. So, if you plan on running a half or full marathon, you’ll need to sprint at 100 percent to achieve the maximum benefit," says Jens Bangsbo.

Effective training for busy lives

It may seem silly to be constantly accelerating and slowing down while out on a run, but consider what you’re missing out on by not doing so. 10-20-30 interval running is a type of workout that, besides improving running times and overall fitness, also comes with a wide range of other health benefits.

This was established in another study by Jens Bangsbo in 2020, in which diabetics lowered their blood sugar and the amount of "dangerous fat" around their organs after ten weeks of 10-20-30 exercise.

"Just as with other high intensity exercises that elevate heart rate, 10-20-30 workouts have a positive effect on health. Among other things, we also see improvements in blood pressure and cholesterol levels. At the same time, interval training is more effective, because you can get into better shape and improve your health in less time than by running at a constant pace," says Bangsbo.

According to Bangsbo, 10-20-30 training  can also feel both easier and more fun.

"Many people find that interval running is more fun due to the changes in pace. And when doing 10-20-30 training , there is also a social element, as runners with different performance level can meet after the ten-seconds period and run together, whichmakes it more enjoyable. With this study, we’ve shown that, even if you "only" run at 80 percent during the sprint, it is still a very effective form of training – which may encourage even more people to opt for this kind of training," concludes Jens Bangsbo.