- Halvard Grendstad is a PhD candidate at the Department of Physical Performance.
- On February 10th, he will defend his dissertation: "Taking a breather: Do physiological changes induced by growth during puberty outweigh those induced by endurance training in youth athletes?"
- Read the dissertation
- Read more about the project "Growth, Maturation, and Training during Puberty."
- Watch the defense on NIH's YouTube channel.
About the study
In this project, we investigated how endurance training affects boys and girls aged 12 to 14 years. The participants were recruited from two distinct groups: one group engaged in endurance sports, and another group who was less active and did not participate in endurance training. We tracked their development of maximal oxygen uptake (VO₂max) and assessed their physical growth, including lung size, heart function, and blood volume—key factors for fitness.
Previous research shows that puberty plays a crucial role in developing VO₂max and the growth of vital organs. Our goal was to determine whether varying amounts of endurance training or types of physical activity could further influence this development.
Results
Our results revealed that children involved in endurance sports had higher levels of VO₂max than their less active peers. However, the development of VO₂max was similar across both groups throughout the study. This indicates that those who engaged in a substantial amount of endurance training did not achieve further improvements beyond what is attributed to growth. We also found that the organs measured—lungs, heart, and blood volume—grew at similar rates regardless of activity level.
To better understand the effects of different training forms, we analyzed the endurance-trained group in more detail in a short training intervention. This group was divided into two subgroups: one received additional interval training over a short period, while the other was restricted from intense training and instead participated in lower-intensity, play-based sessions and basic strength training. We found no differences in development of VO₂max between these subgroups or when compared to the less active group, which did minimal training.
Our conclusion is clear: natural growth during puberty is the most significant factor for improvements in VO₂max. Even high training volumes and intensive endurance training, including interval training, do not provide additional benefits to VO₂max at this age beyond what occurs through normal growth and development.
These findings are particularly relevant for youth sports, where there is a growing trend toward early specialization and adult-like training during adolescence. Since structured endurance training does not appear to enhance VO₂max, our study suggests that more varied and play-based activities could be a better strategy for fostering future elite athletes and retaining children in sports. This aligns with findings from extensive literature reviews showing that the best adult athletes often had a diverse athletic background and engaged in varied activities for longer than those who excelled as youth athletes.
Practical Information
- 10:15-11:00: Trial Lecture
- 13:00-16:00: Defense of the Dissertation: "Taking a breather: Do physiological changes induced by growth during puberty outweigh those induced by endurance training in youth athletes?"
Committee
Chair: Live Steinnes Luteberget, Associate Professor, Norwegian School of Sport Sciences
Opponents:
Professor Alan R. Barker, Children’s Health and Exercise Research Centre, Faculty of Health and Life Sciences, University of Exeter, UK
Research Associate Jon Peter Wehrlin, Swiss Federal Institute of Sport, Magglingen, Switzerland
Supervisors:
Main Supervisor: Jostein Hallén
The defense will be chaired by: Pro-Rector Elin Kolle
The defense is open to the public and will be streamed on NIH's YouTube channel.