Trunk Muscle Endurance and Flexibility as Determinants of Athletic Performance in Elite Adolescent Tennis Players

Investigation of the Relationship Between Trunk Muscle Endurance and Flexibility and Athletic Performance in Elite Adolescent Tennis Players

This study aims to examine how trunk (core) muscle endurance and flexibility relate to athletic performance in elite adolescent tennis players aged 11-18 years. Tennis requires speed, balance, strength, coordination, and repeated high-intensity movements. The trunk region plays an important role in transferring force between the upper and lower body and in maintaining posture and stability during sports activities. However, there is limited research on how trunk physical characteristics influence performance in young elite tennis players.

Participants who actively compete in tennis tournaments and train regularly will complete a set of standardized tests assessing flexibility, trunk muscle endurance, balance, sprint speed, agility, and strength. The results will help researchers understand whether trunk flexibility and endurance are associated with better athletic performance. Findings may guide coaches and health professionals in designing training programs that improve performance and potentially reduce injury risk in young athletes.

Study Overview

• Status: Completed
• Conditions: Athletic Performance; Physical Fitness; Sports Performance; Trunk Muscle Function
• Intervention / Treatment: Other: Physical Performance Assessment

Detailed Description

This cross-sectional descriptive study investigates the relationship between trunk muscle endurance, trunk flexibility, and athletic performance parameters in elite adolescent tennis players. Tennis is a high-intensity intermittent sport requiring rapid acceleration, deceleration, directional changes, and explosive movements. Physical performance depends on multiple components, including strength, flexibility, endurance, and neuromuscular coordination. The trunk region is biomechanically important because it provides proximal stability, supports postural control, and facilitates force transmission between upper and lower extremities during sport-specific movements.

Despite evidence suggesting that trunk function contributes to athletic performance and injury prevention, limited research has focused specifically on elite adolescent tennis players, whose neuromuscular characteristics may differ due to growth and maturation. Therefore, this study aims to clarify associations between trunk physical characteristics and performance outcomes in this population.

Elite tennis players aged 11-18 years who train regularly and compete in official tournaments will be recruited. After informed consent procedures, participants will undergo standardized testing on regular training days following a supervised warm-up protocol.

Assessments include:

Demographic measures: age, sex, height, body weight, body mass index, training frequency, and years of tennis experience.

Flexibility tests: sit-and-reach, trunk lateral flexion, trunk rotation, and trunk extension.

Trunk muscle endurance tests: Biering-Sorensen test, plank test, and side plank test.

Athletic performance tests: Y Balance Test for dynamic balance, 20-meter sprint test for speed, T-drill test for agility, push-up test for upper-extremity endurance, medicine ball throw for upper-body power, and vertical jump for lower-extremity explosive strength.

All measurements will be conducted in the same environment by an experienced assessor using standardized procedures. Statistical analyses will evaluate correlations and predictive relationships between trunk endurance/flexibility variables and performance outcomes.

The results are expected to clarify whether trunk flexibility and endurance are key determinants of athletic performance in adolescent tennis players. Understanding these relationships may support evidence-based training strategies targeting trunk function to enhance performance and reduce injury risk.

• Study Type: Observational
• Enrollment (Actual): 38

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Atakum
    • Samsun, Atakum, Turkey (Türkiye), 55270
      • Ondokuz Mayis University

Participation Criteria

Eligibility Criteria

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

• Sampling Method: Non-Probability Sample

Study Population

Elite adolescent tennis players who are licensed athletes, actively training and competing in tennis clubs. Participants represent trained youth athletes with regular high-frequency training exposure and competitive experience.

Description

Inclusion Criteria:

• Aged between 11 and 18 years
• Elite tennis players actively competing in official tournaments
• Minimum of 3 years of regular tennis training experience
• Participating in tennis training at least 4 days per week
• Ability to understand and follow instructions
• Written informed consent provided by participant and parent/guardian (if under 18)

Exclusion Criteria:

• History of musculoskeletal injury within the past 6 months affecting performance
• Presence of neurological, orthopedic, sensory, or motor disorders
• Any medical condition limiting physical activity
• Current pain that may affect test performance
• Pregnancy

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Elite Adolescent Tennis Players; Elite tennis players aged 11 to 18 years who actively compete and train regularly. Participants undergo standardized assessments of trunk muscle endurance, flexibility, and athletic performance. No intervention is applied; all measurements are observational and conducted under standardized conditions.	Other: Physical Performance Assessment; Participants undergo a standardized assessment protocol including trunk muscle endurance tests, flexibility measurements, balance, sprint, agility, strength, and power performance tests. No therapeutic or training intervention is applied. All procedures are observational and conducted under standardized testing conditions.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
20-Meter Sprint Time	Sprint performance is assessed using a 20-meter sprint test. Participants perform a maximal sprint over a 20-meter distance, and time is recorded in seconds using a stopwatch. Lower time values indicate better sprint performance.	Baseline
T-Drill Agility Test Time	Agility performance is measured using the T-drill test. Participants complete a standardized agility course involving forward sprinting, lateral shuffling, and backward running. Completion time is recorded in seconds. Lower time values indicate better agility performance.	Baseline
Vertical Jump Height	Lower extremity explosive power is assessed using a vertical jump test. Jump height is measured in centimeters. Higher jump height values indicate better explosive strength performance.	Baseline
Medicine Ball Throw Distance	Upper extremity explosive power is evaluated using a medicine ball throw test. The distance the ball is thrown is measured in centimeters. Greater distances indicate better upper body explosive strength performance.	Baseline
Dynamic Balance Performance (Y Balance Test)	Dynamic balance is assessed using the Y Balance Test. Reach distances in the anterior, posteromedial, and posterolateral directions are measured and normalized to leg length (expressed as percentages). Higher percentage values indicate better dynamic balance performance.	Baseline

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Sit-and-Reach Test Distance (cm)	The Sit-and-Reach Test will be used to assess hamstring and lower back flexibility. Participants will sit barefoot with their feet flat against a standardized testing box and reach forward without bending their knees. The final position will be held for 2 seconds. Two trials will be performed, and the best value will be recorded in centimeters.	Baseline
Biering-Sørensen Test Duration	The Biering-Sørensen Test will be used to assess trunk extensor muscle endurance. Participants will be positioned prone on a treatment table with the lower extremities stabilized using straps or manual fixation. The upper body will be positioned beyond the edge of the table at the level of the anterior superior iliac spines. Participants will cross their arms over the chest and maintain the horizontal trunk position as long as possible. The test will be terminated when the trunk position can no longer be maintained. Duration will be recorded in seconds.	Baseline
Trunk Lateral Flexion Distance	Trunk lateral flexion flexibility will be assessed in standing position with feet shoulder-width apart and arms alongside the body. The participant will slide the hand down the thigh while bending laterally without trunk rotation. The distance between the initial and final positions of the third fingertip will be measured in centimeters. Three trials will be performed for each side, and the best value for each side will be recorded in centimeters.	Baseline
Trunk Extension Distance	Trunk extension flexibility will be assessed in standing position facing a wall with the pelvis stabilized. The distance between the suprasternal notch and the wall will be measured at rest and during maximal trunk extension. The difference between the two measurements will be recorded in centimeters. Three trials will be performed, and the highest value will be recorded.	Baseline
Trunk Rotation Distance	Trunk rotation flexibility will be assessed in standing position with feet shoulder-width apart and arms extended at shoulder level. Participants will rotate the trunk maximally to the right and left without moving the pelvis or feet. The distance reached by the fingertips will be recorded using a wall-mounted scale in centimeters. At least two trials will be performed for each direction, and the highest value will be recorded.	Baseline
Plank Test Duration	The plank test will be used to assess anterior trunk muscle endurance. Participants will assume a prone bridge position supported on the forearms and toes, maintaining a straight line from head to heels. The position must be held without hip elevation or sagging. The test will be terminated when proper alignment is lost. Duration will be recorded in seconds.	Baseline
Side Plank Test Duration	The side plank test will be used to assess lateral trunk muscle endurance. Participants will lie on one side with the forearm perpendicular to the body and feet together. When ready, participants will lift the hips off the surface, supporting their body weight on the forearm and feet, maintaining a straight body alignment. The test will be terminated when alignment is lost. The test will be performed on both sides, and duration will be recorded in seconds.	Baseline

Collaborators and Investigators

• Sponsor: Hacettepe University
• Investigators: Principal Investigator: SÜMEYYE ZEHRA Z GÜLER, MSc, Ondokuz Mayıs University

Study record dates

Study Major Dates

• Study Start (Actual): April 1, 2025
• Primary Completion (Actual): June 1, 2025
• Study Completion (Actual): June 1, 2025

Study Registration Dates

• First Submitted: February 26, 2026
• First Submitted That Met QC Criteria: February 26, 2026
• First Posted (Actual): March 3, 2026

Study Record Updates

• Last Update Posted (Actual): March 5, 2026
• Last Update Submitted That Met QC Criteria: March 3, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Trunk; Endurance; Flexibility; Sports performance
• Other Study ID Numbers: OMÜKAEK2024/172

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: The individual participant data will not be shared because of participant privacy considerations and institutional policy

Drug and device information, study documents

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