Young people perform just as well with less effort

Young people involved in endurance sports could just as easily benefit from engaging in varied, technical workouts rather than exerting themselves by doing tough interval training, for example. The results achieved on the pitch or the track would be just as good if they engaged in other, possibly more enjoyable cardio-intensive workouts, and this could also reduce the number of young people dropping out.

Landgraff measuring O2 intake on teenage girl
Hege Wilson Landgraff tested max oxygen intake among youths. The results were not as one would expect. Photo: NIH

A new study shows that endurance training or cardio-intensive workouts, which are essential in many sports, have a different impact on young people during puberty compared to adults.

Portrait of Hege Wilson Landgraff
Hege Elisabeth Wilson Landgraff works at the Department of Physical Performance at NIH. Photo: NIH

Variety and technique

"Cardio-intensive workouts and oxygen uptake are important, but instead of getting stuck into numerous interval training sessions, they could instead engage in varied exercise involving technique and coordination while allowing the fact that they are maturing to take care of increasing their oxygen uptake.

These are the words of Hege Wilson Landgraff who has been studying how endurance training affects 12-16-year-olds.

Her findings show that young people who are maturing benefit as much from varied training involving a lot of technique and coordination as they do from tough interval training. Her studies show that they are able to develop their endurance equally well if they engage in varied training. And more varied training quickly becomes more enjoyable so that fewer young people will drop out.

“But if you want to be good, you can’t avoid training, and you have to train a lot,” says Ms. Landgraff.

Fitness is equivalent to maximal oxygen uptake and indicates the maximum amount of much oxygen the body needs to take up for each kilo of body weight per minute.

Maximal oxygen uptake is largely responsible for determining performance in cardio-intensive sports.

Fitness improves without training

Hege Wilson Landgraff has compared the effects of different types of training. One group that engaged in a lot of endurance or cardio training was compared with a group which trained for around the same number of hours, but which involved much more variation and technique and less endurance.

She has studied whether or not the athletes in the two groups developed differently in terms of maximal oxygen uptake, blood volume and heart size – and what this means for their fitness.
And what did she find mattered most? That they develop, and that it is even more decisive than we might think.

During puberty, young people can grow by more than 10 cm and their weight can increase by more than 10 kg over the course of a year. When their weight increases from less than 40 kg to over 60 kg over the course of three years, the whole body also has to adjust, at least if they want to perform as well as they did previously on the cross-country skiing trail or the football pitch.

Performance in young people who are developing increases in step with their age. This happens entirely without training because heart size, blood volume and muscle mass, etc. increase with sexual maturity and weight and height increases.

Muscular strength, anaerobic capacity and maximal O2 accompany this. Boys who mature early are taller, heavier and more muscular than those who mature late.

Consequently, boys who perform best during puberty often develop early and are larger.

"If young people are to maintain their fitness, the size of their heart and their blood volume need to increase in line with any weight increases,” explains Ms. Landgraff. “And these adjustments in the heart and blood happen of their own accord, entirely without involving the need to engage in training!”

No added effects as a result of cardio-intensive training

Ms. Landgraff says that most of the young people they studied were actively involved in sports. Some of them had done a lot of exercise and consequently they were obviously more adept and often performed better when they were 15 than when they were 12. Some exercises are designed to make young people become more technically capable and their technique improves considerably when they are that age. But some exercises are designed to mainly increase capacity by increasing oxygen intake and muscular strength.

"We asked ourselves the following question: when round-the-clock hormonal changes cause such major increases in both the size of the heart and blood volume, how important is a few hours of cardio-intensive training then?”

This constituted the actual basis for this long-term, demanding project, which started back in 2013.

Hege Wilson Landgraff has been studying a mixed group og boys and girls. She has been following the same young people for several years, between the ages of 12 and 16, and their development varied considerably. The height of her 13-year-olds varied by up to half a metre, and the lightest one weighed 50 kg less than the heaviest one.

Since she started her project in 2012 she has been following up and measuring some young people actively involved in cross-country skiing and some involved in other sports where there is less focus on cardio-intensive training, mainly team sports such as football and handball.

In addition to maximal oxygen uptake, Hege Wilson Landgraff has studied the effects of training on blood volume, haemoglobin levels (red blood cells) and blood plasma levels – and more physical measurements such as muscle and fat volume.

“And we discovered that – contrary to what applies to adults – as long as the young people were active for a few hours per week, cardio-intensive training did have any extra impact on either their heart and blood or their fitness.”

Can breathe a sigh of relief

“So is cardio-intensive training a waste of time for young people? They just grow as well anyway?"

“No, absolutely not. But they could happily benefit from other, more varied ways of training than simply engaging in uniform cardio-intensive training and they can have more fun while exercising,” she says.

This also means that anyone training young people could benefit from planning sessions differently by placing greater emphasis on the more enjoyable aspects.

She says: “Trainers and even parents can breathe a sigh of relief when it comes down to the duration, number and intensity of training sessions. There is no reason why performance on the track or pitch would suffer in either the short or the long term if hard training is carried out as a relay instead of interval training.”

"Consequently, it is reasonable to suppose that fewer young people would drop out, and this in itself is one important sports goal."

Big advantage for boys

However, the study also shows that there is a difference between boys and girls. During puberty, the performance of boys increases much more than that of girls. But according to Ms. Landgraff there is an entirely natural explanation for this.

A technician takes a blood sample from a teen participant.
Blood test were necessary to check oxygen intake. Photo: NIH


“During puberty, boys have more testosterone in their bodies, and they develop more muscle. Girls also experience an increase in muscle mass, but their fat percentage also increases,” she says.

Such a change in body composition is essential if girls are to develop normally. “If this doesn’t happen, the body could suffer from other negative effects. However, because of this, girls will often experience stagnation in their performance during this phase, but it is important to know that this is entirely normal.”

“Is that why more girls than boys stop being involved in sports during their adolescence?”

A teenager receives instructions while running on a treadmill.
Photo: NIH

“Yes, that's right. They discover that they are no longer keeping up with the boys who they could previously beat. This is because girls and boys develop differently. While they experience similar increases in body weight, the muscles of boys develop more and girls gain more fat. This is entirely natural, she explains. “So, when the boys acquire more power to move the same amount of weight, it obviously becomes harder for the girls to keep up compared to previously.”

Technically speaking the girls also have reduced O2-uptake because they have less muscle mass. However, if we were to take this into account and divide their O2-uptake between their muscle mass, these differences between the genders would no longer apply.

"In other words, it is simply the different types of body composition in the two genders which constitutes the difference.”