Cardiorespiratory and muscular fitness in Swedish adolescents
| ISRCTN | ISRCTN15008228 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN15008228 |
| Sponsor | Skandia's Ideas for Life Foundation |
| Funder | Skandia's Ideas for Life Foundation |
- Submission date
- 01/10/2026
- Registration date
- 02/10/2026
- Last edited
- 01/10/2026
- Recruitment status
- Recruiting
- Overall study status
- Ongoing
- Condition category
- Other
Plain English summary of protocol
Background and study aims
There is growing concern that today’s adolescents may have lower physical fitness levels than previous generations. Physical fitness, including cardiorespiratory fitness and muscular strength, is strongly linked to current and future physical and mental health. Despite this, Sweden currently lacks nationally representative data on the fitness levels of adolescents and how these levels vary across different groups.
The SWEFIT study aims to establish national reference values for cardiorespiratory fitness and muscular strength among Swedish adolescents aged 13–14 and 17–18 years. The study will also examine differences in fitness according to sex and socioeconomic background, investigate associations between fitness, lifestyle habits, and mental health, and compare current fitness levels with previous Swedish and international data.
Who can participate?
Students enrolled in grade 7 (aged 13–14 years) and grade 2 of upper secondary school (aged 17–18 years) at participating schools in Sweden are eligible to participate. Participating schools are selected by Statistics Sweden (SCB) using a nationally representative sampling procedure to ensure broad geographic and socioeconomic representation of Swedish adolescents.
Participation is voluntary. Students aged 15 years and older will provide their own informed consent, while parents or guardians will provide consent for participants younger than 15 years.
What does the study involve?
Data collection will take place at participating schools using buses equipped with testing equipment, nearby universities, or fitness centers. Students will attend a testing session with their class and rotate through several assessment stations supervised by trained research staff. Testing is expected to take 120–190 minutes per class.
The study includes:
1. A submaximal cycle ergometer test to estimate cardiorespiratory fitness.
2. Muscle strength tests, including handgrip strength, standing long jump, and bent-arm hang.
3. Measurements of height, weight, blood pressure, and resting heart rate.
4. A digital questionnaire covering physical activity, sedentary behaviour, dietary habits, sleep, tobacco and nicotine use, mental health, and background characteristics.
5. Information on parental education and household income obtained from registers maintained by Statistics Sweden (SCB) to assess socioeconomic background.
All measurements are collected on one occasion, and no intervention or treatment is provided as part of the study.
What are the possible benefits and risks of participating?
The study will also contribute important knowledge about the health and fitness of Swedish adolescents, which may help inform future public health initiatives and policies.
The study involves only low-risk procedures. Some participants may experience temporary fatigue or mild discomfort during the fitness tests, particularly during the cycling test and muscle strength assessments. Participants can stop testing at any time if they wish.
Where is the study run from?
The study is led by researchers at the Swedish School of Sport and Health Sciences (GIH) in Stockholm, Sweden, in collaboration with Karolinska Institutet.
When is the study starting and how long is it expected to run for?
October 2026 to December 2029
Who is funding the study?
Skandia Idéer för livet (Sweden)
Who is the main contact?
Prof. Gisela Nyberg, gisela.nyberg@gih.se
Contact information
Principal investigator, Scientific
Lidingövägen 1
Stockholm
114 86
Sweden
 ORCID ID |
0000-0003-0004-8533 |
|---|---|
| Phone | +46 (0)812053806 |
| gisela.nyberg@gih.se |
Public
Lidingövägen 1
Stockholm
114 86
Sweden
| ORCID ID |
0000-0002-8079-0596 |
|---|---|
| Phone | +46 (0)730913811 |
| karin.kjellenberg@gih.se |
Study information
| Primary study design | Observational |
|---|---|
| Observational study design | Cross sectional study |
| Scientific title | The SWEFIT study: a national survey of cardiorespiratory and muscular fitness in Swedish adolescents |
| Study acronym | SWEFIT |
| Study objectives | 1. To establish nationally representative reference values for physical fitness (cardiorespiratory fitness and muscular strength) among Swedish adolescents aged 13–14 and 17–18 years. 2. To investigate differences in physical fitness according to sex and socioeconomic background. 3. To examine associations between physical fitness and health-related outcomes, including physical activity, sedentary behaviour, diet, sleep, tobacco use, and mental health. 4. To compare current physical fitness levels with previous Swedish and international reference data. |
| Ethics approval(s) |
Approved 13/04/2026, Swedish Ethical Review Authority (Box 2110, Uppsala, 75002, Sweden; +46 (0)104750800; registrator@etikprovning.se), ref: Dnr 2026-01911-01 |
| Health condition(s) or problem(s) studied | Physical fitness (cardiorespiratory fitness, muscular strength), resting heart rate, and blood pressure, height, weight, physical activity, sedentary behaviour, lifestyle factors, and mental health among Swedish adolescents |
| Methodology | This is a national cross-sectional observational study including approximately 4,000 Swedish adolescents aged 13–14 years (grade 7) and 17–18 years (grade 2 of upper secondary school) from approximately 80 schools across Sweden. Schools are selected by Statistics Sweden (SCB) to provide a geographically and socioeconomically representative sample of Swedish adolescents. Participants attend a school-based assessment session conducted by trained research staff. Anthropometric measurements including height and weight are collected using standardized procedures. Resting heart rate and blood pressure are measured following a period of seated rest. Cardiorespiratory fitness is assessed using the Ekblom-Bak submaximal cycle ergometer test. Muscular fitness is assessed using a battery of field-based tests, including standing long jump, handgrip strength and bent-arm hang. Participants complete a digital questionnaire covering demographic characteristics, socioeconomic factors, physical activity, sedentary behaviour, dietary habits, sleep, tobacco and nicotine use and mental health. Mental health outcomes include anxiety symptoms, depressive symptoms, psychosomatic symptoms, life satisfaction and health-related quality of life. Register-based information on parental education and household income is obtained from Statistics Sweden (SCB) and linked to study data using personal identity numbers before the data are pseudonymised for analysis. All measurements are collected once during the study period, and no intervention is provided. The study aims to describe levels of physical fitness, health and lifestyle behaviours among Swedish adolescents and to investigate associations between these factors and socioeconomic characteristics. |
| Intervention type | Other |
| Primary outcome measure(s) |
|
| Key secondary outcome measure(s) |
|
| Completion date | 31/12/2029 |
Eligibility
| Participant type(s) | |
|---|---|
| Age group | Mixed |
| Lower age limit | 13 Years |
| Upper age limit | 18 Years |
| Sex | All |
| Target sample size at registration | 4000 |
| Key inclusion criteria | 1. Students enrolled in grade 7 (aged 13–14 years) or grade 2 of upper secondary school (aged 17–18 years) at participating schools in Sweden 2. Provision of informed consent by participants aged 15 years or older, or parental/guardian consent for participants younger than 15 years 3. Ability to understand the study information and complete study procedures |
| Key exclusion criteria | 1. Students outside the target age groups (13–14 years and 17–18 years) 2. Students attending schools not selected for participation in the study 3. Students unable to understand study information in Swedish sufficiently to provide informed consent and complete study procedures 4. Students or guardians who do not provide informed consent |
| Date of first enrolment | 02/10/2026 |
| Date of final enrolment | 28/12/2028 |
Locations
Countries of recruitment
- Sweden
Study participating centres
Results and Publications
| Individual participant data (IPD) Intention to share | No |
|---|
Editorial Notes
01/10/2026: Study's existence confirmed by the Swedish Ethical Review Authority.
