FIT FIRST for the Bones (FIT FIRSTftB)

June 15, 2026 updated by: University of Southern Denmark

FIT FIRST for the Bones - Frequent Intense Training for Lifelong Bone Health

This study aims to conduct a cluster RCT intervention study with adolescents in Denmark and investigate whether the FIT FIRST concept can improve young people's bone health. We hypothesize that students from the schools randomized to the intervention arm will show greater improvements in bone health than students randomized to the control arm. The experiment will be of societal relevance in relation to evidence for the effects of implementing high-intensity physical activity in school.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Enrolling by invitation

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

In 2018, the FIT FIRST 10 concept was developed for 6-9 year olds. It included 10 sports, all of which were modified to include both strength and cardio training, but based on sports that you can go to in your spare time, as opposed to many other classic school activities such as roundball, stickball and catch. In 2020, the FIT FIRST 20 concept for 10-12 year olds was developed to include 20 sports, and the FIT FIRST Teen material with more than 20 sports has been released in 2024.

In short, all versions of the FIT FIRST concept are built on the principles of using multiple sports activities modified for the school environment, with a focus on high intensity, high commitment and inclusion. The use of several sports activities that are modified for the school environment can also affect recess and leisure sports, as students are introduced to many fun activities that are easy to organize themselves and/or go to clubs in their spare time.

The implementation of the FIT FIRST concept involves training teachers to deliver the program, which has been developed by experienced staff from the University of Southern Denmark (SDU), the Sports Confederation of Denmark (DIF) and Team Denmark. These partners have developed 3-6 lessons for each of the sports, all using exercises and activities carried out in pairs or small groups. All the lessons included in the FIT FIRST Teen manual are designed to provide high-intensity strength and cardio training and to be motivating for children to participate, according to self-determination theory.

a) Design: A cluster-randomized trial design is used, where school classes are randomly divided into an intervention group that implements the FIT FIRST training concept, and a control group that continues regular schooling.

c) Practical implementation: Schools on Funen will be invited via e-mails, newsletters from the Danish Sports Confederation and social media, and can sign up with 1-2 classes. All students at the participating schools can participate in the survey. The first 10 schools that agree to participate in the study will be randomized into two arms, intervention and control. The intervention arm will implement 3 weekly 40-minute FIT FIRST Teen lessons over the course of 18 weeks, equivalent to half a school year. The teachers who will be responsible for the teaching are trained on a 6-hour theoretical/practical course and the schools receive an equipment package with balls, cones and vests for use in the teaching. The FIT FIRST intervention contains activities that are common in physical education and movement education and will therefore involve the whole class, including the students who are not test subjects in this study. The workout is designed to have elements of high-heart rate training and elements that stimulate bones and muscles. All exercises are based on sports activities you can do in your spare time.

On the test days, all students will also join the class on a trip to the University of Southern Denmark, where only test subjects with consent will participate in trial activities, while others will only participate in sports activities organized by their teacher on the university's campuses, where there are facilities such as a swimming pool and jumping center that make it attractive for the classes to visit.

The schools in the control arm will continue their normal sports curriculum and they will receive the intervention at the end of the trial as a thank you for their efforts. Here, too, the whole class comes on a trip and is allowed to borrow the university's sports facilities.

Bone density will be measured with a whole-body DXA scan before and after the 18 weeks, and bone markers in the blood will be measured via a venous blood sample. In addition, hand grip strength is measured The project will run in 2026.

Tests and measurements:

Anthropometric measurements: Measurement of height and weight is carried out with a portable stadiometer and scale, respectively.

DXA scan: A full-body DXA scan is performed to determine bone mineralization and body composition (fat percentage and muscle mass). The DXA scanner is iDXA Lunar, GE Healthcare. The DXA scan will take place at a hospital or university located close to the school. The test is performed by a radiographer or trained research staff after 0 and 12 weeks.

Blood samples: Blood sampling is performed with a cannula from a vein in the arm for analysis of the concentrations of Osteocalcin, procollagen type I N-terminal propeptide (PINP) and β-C-terminal telopeptide of type I collagen (CTX-I). The blood is collected in 4 ml EDTA glass. Thus, a total of 8 ml of venous blood is collected from each test subject over the two visits.

Muscle strength: Handgrip strength is measured with a handgrip dynamometer (CAMRY).

Intervention The classes in the intervention group will carry out 3 weekly sessions of 40 minutes duration, where they use the FIT FIRST concept with high-intensity, fun and involving training based on sports that you can go to in your spare time. It will be their own teachers who are responsible for the teaching after they have been on a 6 hour course to learn how to use the concept.

4. Statistical considerations.

a) The size of the sample (200 students from a total of 10 classes, 5 in each group) is selected based on an expected effect size of 0.025 g/cm2 on whole-body bone density and a standard deviation of 0.035 g/cm2. Intra Cluster Correlation is expected to be 0.02 g/cm214-16 and the size of the classes is expected to be 20 students on average.

5. Subjects A. Inclusion criteria

  • Healthy boys and girls in 7th+8th grade aged 12-14.99 years.
  • Informed consent of the parents/authority holder(s).
  • Willingness to carry out training and testing.

B. Exclusion Criteria:

• Subjects who are not considered by the researchers to be suitable to follow the protocol/testing and training program.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
200

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Denmark
    • Funen
      • Odense, Funen, Denmark, 5230
        • University of Southern Denmark

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Child

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Part of participating classes

Exclusion Criteria:

  • None

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Intervention
3x40 min High Intense training pr week for 18 weeks
Behavioral: FIT FIRST
Frequent Intense Training (3x40 min pr. week for 18 weeks
No Intervention: Control
Normal behavior

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
whole-body bone mineral density
Time Frame: From enrollment to the end of treatment at 18 weeks
A full-body DXA scan is performed to determine bone mineralization
From enrollment to the end of treatment at 18 weeks

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
procollagen type I N-terminal propeptide (PINP)
Time Frame: From enrollment to the end of treatment at 18 weeks
Blood sampling is performed with a cannula from a vein in the arm for analysis of the concentrations
From enrollment to the end of treatment at 18 weeks

Other Outcome Measures

Other Outcome Measures

For clinical trials, a planned measurement described in the protocol that is used to determine the effect of an intervention/treatment on participants. For observational studies, a measurement or observation that is used to describe patterns of diseases or traits, or associations with exposures, risk factors, or treatment. Types of outcome measures include primary outcome measure and secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Osteocalcin
Time Frame: From enrollment to the end of treatment at 18 weeks
Blood sampling is performed with a cannula from a vein in the arm for analysis of the concentrations
From enrollment to the end of treatment at 18 weeks
β-C-terminal telopeptide of type I collagen (CTX-I)
Time Frame: From enrollment to the end of treatment at 18 weeks
Blood sampling is performed with a cannula from a vein in the arm for analysis of the concentrations
From enrollment to the end of treatment at 18 weeks
Leg BMD
Time Frame: From enrollment to the end of treatment at 18 weeks
full-body DXA scan is performed to determine bone mineralization
From enrollment to the end of treatment at 18 weeks

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
University of Southern Denmark

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
January 12, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
December 20, 2026

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
December 20, 2026

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
June 15, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
June 15, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
June 22, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
June 22, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
June 15, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
June 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • S-20250081

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Not possible within the Danish GDPR regulations

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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