Effects of 8-Week CrossFit-Based Concurrent Training on Fitness, Body Composition, and Psychological Outcomes in Schoolchildren

Effects of an 8-Week CrossFit-Based Concurrent Training Program on Physical Fitness, Body Composition, and Psychological Outcomes in Schoolchildren: A Randomized Controlled Trial Protocol

This study examines the effects of an 8-week CrossFit-based concurrent training program in boys and girls aged 7 to 11 years, comparing an experimental group (n=15) with a control group (n=15). The aim is to assess changes in strength, cardiorespiratory fitness, body composition, and psychological variables such as anxiety, stress, and self-esteem, using field-based physical tests (CMJ, Course Navette, handgrip strength, etc.) and validated questionnaires. The study follows a randomized controlled trial design with pre- and post-intervention assessments. The experimental group will complete two weekly CrossFit sessions adapted for children, while the control group will maintain their usual routine without structured physical training. The hypothesis states that the intervention will significantly improve both physical performance and psychological well-being in the experimental group compared to the control group.

Study Overview

• Status: Not yet recruiting
• Conditions: Body Composition; Children; Physical Fitness; Psychology, Child; Crossfit
• Intervention / Treatment: Other: CrossFit training

Detailed Description

This study is a randomized controlled trial designed to examine the effects of an 8-week CrossFit-based concurrent training program on both physical fitness and psychological well-being in school-aged children (boys and girls aged 7 to 11 years). The sample will be drawn from a primary school in Córdoba (Spain) and will be randomly assigned to either an experimental group (n=15) or a control group (n=15).

The experimental group will participate in a supervised CrossFit Kids program, consisting of two weekly sessions of 50 minutes each. These sessions will include functional, age-appropriate high-intensity exercises structured into four parts: warm-up (mobility and games), strength work (technical and developmental exercises), metabolic conditioning (METCON), and a final cool-down or game-based activity. The control group will continue with their usual daily routine without any structured physical training during the intervention period.

The study will assess changes in physical fitness variables, including muscular strength (countermovement jump, handgrip strength, standing long jump, and medicine ball throw), cardiorespiratory fitness (Course Navette test, burpees, abdominal endurance tests, and step tests), and body composition indicators such as BMI, waist circumference, and waist-to-height ratio. In addition, psychological outcomes will be evaluated using validated instruments measuring state and trait anxiety (State-Trait Anxiety Inventory), daily stress (Children's Daily Stress Inventory) and self-esteem (Rosenberg Self-Esteem Scale).

Measurements will be taken before and after the intervention to compare intra- and inter-group changes. The study also explores potential relationships between improvements in physical fitness and psychological outcomes.

The main hypothesis is that participation in the CrossFit-based concurrent training program will lead to significant improvements in strength, endurance, body composition, and psychological well-being (reduced anxiety and stress and improved self-esteem) compared to the control group, highlighting the potential of this training approach as an effective and comprehensive intervention for children.

• Study Type: Interventional
• Enrollment (Estimated): 30
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: José Manuel Jurado Castro; Phone Number: +34 957 21 37 00; Email: jose.jurado@imibic.org

Study Locations

• Spain
  • Córdoba
    • Córdoba, Córdoba, Spain, 14004
      • IMIBIC

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Age: 7-11 years.
• Students enrolled at CEIP Pablo García Baena (Córdoba).

For the experimental group:

• Availability to attend the Triple XXX Box (Polígono Pedroches, C. los Alfareros, Parcel 119, 14014 Córdoba), where both assessments and training sessions will be conducted.
• Availability to attend training sessions twice per week for the 8-week intervention period.
• No participation in extracurricular physical activity prior to the start of the CrossFit program.

For the control group:

No participation in extracurricular physical activity. Informed consent signed by parents or legal guardians. No medical, psychological, or behavioral contraindications that would prevent participation in physical activity.

Exclusion Criteria:

• Children with musculoskeletal injuries, diseases, or medical, psychological, or behavioral conditions that limit physical activity or interfere with the assessment of outcomes.
• Inability or anticipated difficulty in regularly attending training sessions.
• Refusal of parents or legal guardians to provide informed consent.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Crossfit training	Other: CrossFit training; The experimental arm will receive an 8-week concurrent training intervention based on a CrossFit program adapted for children, with a frequency of two 50-minute sessions per week. Each session will be structured into a warm-up (mobility exercises and games), strength training (technical and functional exercises), metabolic conditioning (METCON), and a cool-down phase. The program will be supervised by qualified professionals to ensure safety and proper execution of the exercises.; Other Names: Body composition; Psychological Outcomes
No Intervention: Control; The control arm will not receive any structured exercise intervention during the study period and will continue with their usual daily school routine. This will allow comparison of changes in physical and psychological outcomes between both groups.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Countermovement Jump Test (CMJ) - Explosive Strength Test	The countermovement jump (CMJ), is used to assess explosive strength of the lower limbs. In this test, participants begin in an upright standing position with their hands placed on their hips to avoid arm swing contribution. They are instructed to perform a maximal vertical jump following a rapid downward countermovement, descending to approximately 90° of knee flexion, and then immediately jumping as high as possible.	Week 1 (Day 1), Week 8 (Day 16)
Standing Long Jump	This test consists of performing a horizontal jump using both feet simultaneously, starting from the same level. A preliminary jump is not allowed. The maximum horizontal distance achieved is recorded, measuring from the starting line to the rearmost point of the shoe closest to that line. Upon landing, the participant must maintain balance and remain stationary.	Week 1 (Day 1), Week 8 (Day 16)
Medicine Ball Throw Test	The medicine ball throw test (2 kg) is performed from an upright standing position, holding the ball with both hands above the head. Participants are required to throw the ball as far as possible by performing a flexion-extension movement of the legs, with or without trunk extension.	Week 1 (Day 1), Week 8 (Day 16)
20 m Shuttle Run Test (Course-Navette)	In the 20 m shuttle run test, participants run back and forth between two lines set 20 m apart, with progressively increasing speed. The initial running speed is 8.5 km/h and increases by 0.5 km/h every minute. Each increase in speed corresponds to a new level.	Week 1 (Day 1), Week 8 (Day 16)
Plank Hold Time	The plank protocol requires participants to maintain a static prone position, with only the forearms and toes in contact with the ground. Proper form requires feet together with toes pointing downward, elbows positioned under the shoulders at forearm width, and hands clasped together on the floor.	Week 1 (Day 1), Week 8 (Day 16)
Burpess	To perform a burpee, participants begin with feet shoulder-width apart and lower into a squat by bending the knees. They then place their palms on the floor and jump back into a plank position with arms extended, ensuring hands face forward, feet rest on the toes, and the back remains straight. Next, they perform a push-up by bending the elbows and returning to the plank position. Then, they jump forward into a squat position, keeping hands on the ground, hips lowered, thighs parallel to the floor, and knees positioned between the elbows. Finally, they jump vertically from the squat position, extending the arms overhead during the jump.	Week 1 (Day 1), Week 8 (Day 16)
Step Test	This test consists of stepping up and down on a platform approximately 30 cm in height, maintaining a constant speed and rhythm.	Week 1 (Day 1), Week 8 (Day 16)
State-Trait Anxiety Inventory for Children	State-Trait Anxiety Inventory for Children is a psychological instrument designed to measure two dimensions of anxiety in children: state anxiety, referring to temporary or situational anxiety, and trait anxiety, which assesses the general tendency to experience anxiety.	Week 1 (Day 1), Week 8 (Day 16)
Children's Daily Stress Inventory	This test aims to assess daily stress in children by evaluating how common experiences, such as school, family, and social issues, contribute to stress levels.	Week 1 (Day 1), Week 8 (Day 16)
Rosenberg Self-Esteem Scale	The Rosenberg Self-Esteem Scale assesses an individual's self-worth through a series of statements reflecting overall self-evaluation.	Week 1 (Day 1), Week 8 (Day 16)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Body composition	Body composition will be assessed using bioelectrical impedance analysis, with particular emphasis on body fat percentage. Measurements will be conducted in accordance with the protocol established by the International Society for the Advancement of Kinanthropometry (ISAK).	Week 1 (Day 1), Week 8 (Day 16)
Perceived Exertion	Perceived exertion will be measured using a pictorial and verbal category-ratio scale designed for children.	Week 1 (Day 1), Week 8 (Day 16)

Collaborators and Investigators

• Sponsor: Maimónides Biomedical Research Institute of Córdoba
• Collaborators: Universidad de Córdoba; Escuela Universitaria de Osuna

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): June 1, 2026
• Study Completion (Estimated): July 1, 2026

Study Registration Dates

• First Submitted: April 20, 2026
• First Submitted That Met QC Criteria: April 20, 2026
• First Posted (Actual): April 27, 2026

Study Record Updates

• Last Update Posted (Actual): April 30, 2026
• Last Update Submitted That Met QC Criteria: April 25, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: children; anxiety; stress; self-esteem; body composition; exercise training; Physical Fitness; crossfit
• Additional Relevant MeSH Terms: Mental Disorders; Anxiety Disorders; Physiological Phenomena; Biochemical Phenomena; Chemical Phenomena; Body Constitution; Metabolism; Body Composition
• Other Study ID Numbers: SICEIA-2025-000408

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No