The Effect of Training Frequency on Explosive Strength in Adolescent Tennis Players During a Six-Week Functional Training Program

April 23, 2026 updated by: alyildirim, Biruni University

Adolescence is a period characterized by rapid growth and development, characterized by intense structural, functional, and neuromuscular changes in the musculoskeletal system. The rapid height growth and proportional changes that occur during this period can negatively impact athletic performance by disrupting muscle strength and flexibility. Deficiencies in lower extremity muscle strength, in particular, can lead to decreased performance and increased injury risk in sports requiring high agility, balance, and explosive power, such as tennis.

Functional training programs are holistic exercise approaches that aim to improve neuromuscular control, balance, coordination, and muscle strength by simultaneously training multiple muscle groups. This type of training is particularly important in adolescent athletes because it supports the development of strength, endurance, and explosive power. Training frequency, in turn, plays a decisive role in muscle adaptation and performance enhancement by influencing the balance between loading and recovery.

Literature contains limited studies directly examining the effects of functional training frequency on explosive power performance in young athletes. Most existing research has focused on adult or professional athletes, and experimental studies comparing the effects of different training frequencies in adolescent tennis players are insufficient.

In this context, the aim of our study was to examine the effects of a six-week functional training program implemented at different training frequencies on lower extremity explosive strength parameters in adolescent tennis athletes.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Adolescence is a dynamic period accompanied by rapid growth and development, characterized by intense structural, functional, and neuromuscular changes in the musculoskeletal system. During this period, weakness in the lower extremity muscles can lead to decreased performance and increased injury risk in sports requiring agility, balance, and explosive power, such as tennis.

Functional training programs are comprehensive exercise approaches that improve neuromuscular coordination, balance, and stabilization by simultaneously activating multiple muscle groups. These types of training are particularly important for young athletes because they support sport-specific movement patterns, increase muscle strength, and optimize the energy transfer chain. Training frequency is a key variable in determining muscle adaptation, recovery time, and load balance. Therefore, studies examining the effects of different training frequencies on explosive power development in young tennis athletes are of great scientific and practical value.

Healthy adolescent tennis players who volunteer to participate will be included in the study. After recording demographic and sport-specific information, participants' explosive strength performance will be assessed using the Countermovement Jump (CMJ), Squat Jump (SJ), Single Leg Jump (SLJ), and Reactive Strength Index (RSI) tests. Participants will be randomly assigned to two groups: the first group will participate in a 60-minute functional training program once a week, and the second group will participate in a 60-minute functional training program three times a week. The programs will last six weeks, and all sessions will be conducted by the same physiotherapist. Assessments will be conducted before and after the six-week training program. The study employed a two-group, pretest-posttest design. This study aims to demonstrate the effects of different training frequencies on explosive strength development in adolescent tennis athletes, contributing to the scientific basis of training plans for young athletes and to optimize performance.

Study Type

Interventional

Enrollment (Actual)

30

Phase

  • 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

  • Turkey (Türkiye)
    • Maltepe
      • Istanbul, Maltepe, Turkey (Türkiye), 34844
        • Sportplus Tennis Academy

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

Ages Eligible for Study

  • Child
  • Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Adolescent tennis players aged 12-18 years.
  • Have at least two years of regular tennis training history.
  • Regularly practice tennis at least three days a week.
  • Have not had an acute injury or surgery affecting the lower extremities in the last six months.
  • Have the physical ability to fully complete explosive strength tests (CMJ, SJ, SLJ, RSI).
  • Individuals who voluntarily agreed to participate in the study and provided written consent from their parents.

Exclusion Criteria:

  • Those with ongoing pain, instability, or deformity in the knee, hip, ankle, or spine area.
  • Those who have undergone a musculoskeletal physical therapy or rehabilitation program within the last 6 months.
  • Those with a systemic disease that may affect neurological, vestibular, or balance.
  • Those who experience pain or fatigue to the extent that they cannot complete postural analysis or performance tests.
  • Those who do not have a regular sports history or have not trained regularly in the last 3 months.
  • Participants who exhibited a lack of cooperation during the assessment process that could compromise measurement consistency.

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: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Other: Low-Frequency Functional Training Group (LFFT)
Participants in this group performed the functional training program once per week for six consecutive weeks. Each session lasted approximately 60 minutes and included dynamic warm-up, multi-joint functional exercises, and cool-down activities supervised by the same physiotherapist.
Other: Low-Frequency Functional Training Group (LFFT)
Participants in this group performed the same functional training program once per week for six consecutive weeks. Each 60-minute session followed the same structure as the low-frequency program and was conducted under identical supervision and environmental conditions.
Other Names:
  • exercise
Experimental: High-Frequency Functional Training Group (HFFT)
Participants in this group performed the same functional training program three times per week for six consecutive weeks. Each 60-minute session followed the same structure as the low-frequency program and was conducted under identical supervision and environmental conditions.
Other: High-Frequency Functional Training Group (HFFT)
Participants in this group performed the same functional training program three times per week for six consecutive weeks. Each 60-minute session followed the same structure as the low-frequency program and was conducted under identical supervision and environmental conditions.
Other Names:
  • exercise

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Countermovement Jump Test (CMJ)
Time Frame: 6 weeks
The participant performs a rapid squat from an upright position with hands on hips, followed by a maximum vertical jump. This assesses lower extremity explosive strength and elastic energy utilization.
6 weeks
Squat Jump (SJ) Test
Time Frame: 6 weeks
The participant is fixed in a position of approximately 90° flexion of the knee and hip joints, then performs a maximum vertical jump without using the arms. It measures pure concentric muscle strength.
6 weeks
Reactive Strength Index (RSI) Test
Time Frame: 6 weeks
It's typically performed using a drop jump protocol. The participant jumps onto the platform from a specific height and bounces back up as quickly as possible after contact with the ground. RSI is calculated based on jump height and ground contact time; it measures reactive strength and stretch-shortening cycle (SSC) effectiveness.
6 weeks
Standing Long Jump (SLJ) Test
Time Frame: 6 weeks
The participant stands with their feet parallel and jumps as far forward as possible using their arms. Lower extremity explosive strength is assessed by measuring the jump distance.
6 weeks
Assessment of normal joint motion
Time Frame: 6 weeks
The Normal Joint Motion Assessment (NJM) Test is an objective method used to measure joint range of motion. In the study, participants' hip and knee joint flexion and extension angles will be assessed using the NJM test using a universal goniometer. Measurements will be made using active range of motion, and each measurement will be repeated three times and averaged.
6 weeks

Collaborators and Investigators

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

Sponsor

Biruni University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

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)

February 10, 2026

Primary Completion (Actual)

March 30, 2026

Study Completion (Actual)

April 5, 2026

Study Registration Dates

First Submitted

January 24, 2026

First Submitted That Met QC Criteria

February 6, 2026

First Posted (Actual)

February 10, 2026

Study Record Updates

Last Update Posted (Actual)

April 28, 2026

Last Update Submitted That Met QC Criteria

April 23, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 1071

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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