Muscle Adaptations in Children and Adults Following Twelve Weeks of Flywheel or Weight Stack Resistance Exercise

NCT06698055 | Completed

• 1 other identifier: RJonkopingC KidREx
• Study Type: interventional
• Target: 91
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of this trial is to compare resistance exercise using traditional techniques and flywheel training to controls in healthy children ages nine to 13 and adults ages 18 to 50. The main questions it aims to answer are:

• The degree of response to resistance exercise in children compared to adults regarding muscle hypertrophy and strength?
• Is there a negative impact on the physis of children due to resistance exercise? Participants will be randomized to one of three groups, control, traditional resistance exercise, or flywheel. Following a baseline battery of tests, they will enter a 12-week training period, using leg press and leg extension. Additionally, post-training tests are conducted, and an eight-week detraining period commences followed by new tests. Researchers will compare children and adults and each intervention arm to see if children can achieve muscle hypertrophy, the degree and rate of changes in strength, and the potential impact on the physis.

Conditions

Resistance Exercise; Muscle Hypertrophy; Skeletal Muscle; EMG; Magnetic Resonance Imaging; Growth Plate Early Closing; Children, Adult

Keywords

Skeletal Muscle; Resistance Exercise; Magnetic Resonance Imaging; EMG; Muscle Hypertrophy; Flywheel Training; Strength Training in Children and Adolescents; Growth Plate; Muscle Adaptation; Muscle Memory; Histology; Immunohistochemistry; Transcriptomics; Methylomics; Proteomics; Functional Outcomes; Physical Activity Monitoring; Physical Self Esteem

Outcome Measures

Primary Outcomes (1)

• Change from Baseline Muscle Volume Following 12 Weeks of Resistance Exercies

  The groups of children and adults will undergo magnetic resonance imaging of the anterior thigh in a standardized fashion. Subsequently, the muscle volume is calculated by contouring cross-sectional area of muscle. Primary analysis is muscle growth of the m. quadriceps femoris in the two active comparator groups compared to the control group.

  Time Frame: Before intervention start (0 weeks) and following twelve weeks of training (12 weeks)

Secondary Outcomes (22)

• Changes in muscle thickness

  Time Frame: Prior to intervention start, biweekly during the intervention period (i.e., after two, four, six and eight weeks). Additional scans will be performed following the end of intervention (12 weeks) and the end of detraining (20 weeks).

• Change from baseline in rate of physeal closure following resistance exercise

  Time Frame: Baseline (0 weeks), post training (12 weeks) and post detraining (20 weeks)

• Change in muscle volume at 20 weeks

  Time Frame: Before intervention start (0 weeks) and end of intervention (12 weeks) compared to volume following the detraining period (20 weeks)]

• Changes in peak torque during isokinetic concentric and eccentric knee extension and flexion

  Time Frame: Baseline (0 weeks), post training (12 weeks) and post detraining (20 weeks)

• Changes in power during isokinetic concentric and eccentric knee extension and flexion

  Time Frame: Baseline (0 weeks), post training (12 weeks) and post detraining (20 weeks)

Other Outcomes (6)

• Activity level (adults)

  Time Frame: Starting one week prior to intervention start and ending one week after detraining time point, a total of 22 weeks.

• Monitoring of physical activity level (children)

  All monitors will be worn for one week at three-time points (baseline, 12 weeks, 20 weeks) during the intervention

• Questionnaire based assessment of physical activity (children)

  Baseline (0 weeks), post training (12 weeks) and post detraining (20 weeks)

Study Arms (6)

aFW = Flywheel resistance exercise intervention group adults

ACTIVE COMPARATOR

FW undergo a twelve-week training intervention with alternating two to three sessions per week. At each training session the participant will perform four sets of leg press and a leg extension with seven repetitions per set in each machine were resistance is provided by a flywheel and a weight stack respectively.

Other: Flywheel Resistance Exercise

aWS = Weight stack resistance exercise intervention group adults

ACTIVE COMPARATOR

WS undergo a twelve-week training intervention with alternating two to three sessions per week. At each training session the participant will perform four sets of leg press and a leg extension with seven repetitions per set in each machine were resistance is provided by a flywheel and a weight stack respectively.

Other: Weight Stack Resistance Exercise

aCON = Control group adults

NO INTERVENTION

The CON group will continue living as normally with the aim of remaining at a constant activity level like that at baseline. All groups undergo a baseline test battery witch is repeated following the end of the training period. After the training period all groups enter in to a detraining period were no weight training of the lower limb will be conducted for eight weeks. Following the detraining period the test battery will once more be repeated.

cFW = Flywheel resistance exercise intervention group children

ACTIVE COMPARATOR

FW undergo a twelve-week training intervention with alternating two to three sessions per week. At each training session the participant will perform four sets of leg press and a leg extension with seven repetitions per set in each machine were resistance is provided by a flywheel and a weight stack respectively.

Other: Flywheel Resistance Exercise

cWS = Weight stack resistance exercise intervention group children

ACTIVE COMPARATOR

WS undergo a twelve-week training intervention with alternating two to three sessions per week. At each training session the participant will perform four sets of leg press and a leg extension with seven repetitions per set in each machine were resistance is provided by a flywheel and a weight stack respectively.

Other: Weight Stack Resistance Exercise

cCON = Control group children

NO INTERVENTION

The CON group will continue living as normally with the aim of remaining at a constant activity level like that at baseline. All groups undergo a baseline test battery witch is repeated following the end of the training period. After the training period all groups enter in to a detraining period were no weight training of the lower limb will be conducted for eight weeks. Following the detraining period the test battery will once more be repeated.

Interventions

Flywheel Resistance Exercise OTHER

FW is conducted in a leg extension machine (LegExx, Exxentric, Stockholm, Sweden) and leg press machine (YoYo™ Leg Press, nHANCE, Sweden).

aFW = Flywheel resistance exercise intervention group adults; cFW = Flywheel resistance exercise intervention group children

Weight Stack Resistance Exercise OTHER

WS is conducted in a leg extension machine (Seated leg press, Nordic Gym, Bollnäs, Sweden) and a leg press machine (Seated leg extension, Nordic Gym, Bollnäs, Sweden)

aWS = Weight stack resistance exercise intervention group adults; cWS = Weight stack resistance exercise intervention group children

Eligibility Criteria

• Age: 9 Years - 50 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Child (0-17), Adult (18-64)

You may not qualify if:

• Neuromuscular disease.
• Previous or current musculoskeletal injury, primarily of the lower limb, preventing resistance exercise.

Sponsors & Collaborators

• Björn Alkner: lead
• Karolinska Institutet: collaborator
• Umeå University: collaborator
• Medical Research Council of Southeast Sweden: collaborator
• Swedish Research Council for Sport Science: collaborator
• Linkoeping University: collaborator
• The Swedish Research Council: collaborator

Study Sites (1)

Department of Orthopaedic Surgery, Höglandssjukhuset District Hospital Eksjö

Eksjö, Region Jönköping County, 57581, Sweden

Location

Study Officials

• Björn A Alkner, MD, PhD

  Department of Orthopaedic Surgery, Eksjö, Region Jönköping County and Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: OUTCOMES ASSESSOR
• Purpose: OTHER
• Intervention Model: PARALLEL
• Sponsor Type: OTHER GOV
• Responsible Party: SPONSOR INVESTIGATOR
• PI Title: Principal Investigator, MD, PhD, Associate professor

Model Details: Randomized controlled resistance exercise intervention study

Study Record Dates

• First Submitted: May 29, 2023
• First Posted: November 20, 2024
• Study Start: August 28, 2022
• Primary Completion: February 2, 2025
• Study Completion: February 12, 2025
• Last Updated: December 16, 2025

Record last verified: 2025-04

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ICF, CSR, ANALYTIC CODE
• Time Frame: Upon study completion
• Access Criteria: Upon reasonable request

Locations

SE (1)