An interventional study of CrossFit training in Children, Crossfit and Psychology, Child, sponsored by Maimónides Biomedical Research Institute of Córdoba. Not yet recruiting at 1 site in Spain. Open to participants aged 7 Years to 11 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-04-30.
Sponsored by Maimónides Biomedical Research Institute of Córdoba · Not applicable, Interventional, and Other
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.
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.
For the experimental group:
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:
Other: CrossFit training
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.
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.
Also known as: Body composition, Psychological Outcomes
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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: Week 1 (Day 1), Week 8 (Day 16)
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).
Time frame: 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.
Time frame: Week 1 (Day 1), Week 8 (Day 16)
Plan to share: No
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Maimónides Biomedical Research Institute of Córdoba