Frontal Plane Knee Projection Angle and Functional Performance in Adolescent Female Volleyball Players (FPPA-DBA)

Investigation of the Relationship Between Frontal Plane Knee Projection Angle and Dynamic Balance, Agility, and Ankle Dorsiflexion Mobility in Adolescent Female Volleyball Players

This observational study aims to examine the relationship between frontal plane knee projection angle, dynamic balance, agility performance, and ankle dorsiflexion mobility in adolescent female volleyball players. Frontal plane knee projection angle will be assessed during a single-leg squat using two-dimensional video analysis. Dynamic balance will be evaluated with the Lower Quarter Y-Balance Test, agility with the T-Test, and ankle dorsiflexion mobility with the Weight-Bearing Lunge Test.

All measurements will be completed in a single session under standardized field conditions, and no intervention or experimental treatment will be applied. By investigating how frontal plane knee alignment is associated with functional performance measures, this study may help improve the understanding of biomechanical factors related to movement quality and injury risk in adolescent female volleyball players.

Study Overview

• Status: Completed
• Conditions: Dynamic Knee Valgus; Agility; Dynamic Balance; Ankle Dorsiflexion

Detailed Description

This observational, cross-sectional study aims to investigate the relationship between frontal plane knee projection angle (FPPA), dynamic balance, agility performance, and ankle dorsiflexion mobility in adolescent female volleyball players. Volleyball is a sport that requires repeated jumping, landing, lateral movements, and rapid changes of direction, which place considerable biomechanical demands on the lower extremities. In adolescent female athletes, lower-limb movement patterns may be influenced by growth, maturation, and neuromuscular control, making this population important for biomechanical assessment.

The primary study variable will be frontal plane knee projection angle, assessed during a single-leg squat using two-dimensional video analysis. Secondary measures will include dynamic balance assessed with the Lower Quarter Y-Balance Test, agility assessed with the T-Test, and ankle dorsiflexion mobility assessed with the Weight-Bearing Lunge Test. All assessments will be completed in a single session under standardized field conditions. No intervention, treatment, or experimental exercise program will be applied.

The study is designed to explore whether frontal plane knee alignment is associated with functional performance measures in adolescent female volleyball players. A better understanding of these relationships may contribute to the identification of biomechanical characteristics related to lower-extremity movement quality and potential injury risk in this population.

• Study Type: Observational
• Enrollment (Actual): 70

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Ödemiş
    • Izmir, Ödemiş, Turkey (Türkiye), 35750
      • AB Volleyball Academy

Participation Criteria

Eligibility Criteria

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

• Sampling Method: Non-Probability Sample

Study Population

The study population consisted of adolescent female volleyball players aged 10 to 19 years who were regularly training at least 3 days per week at AB Volleyball Academy in Izmir, Türkiye. Only participants who had reached menarche and met all eligibility criteria were included.

Description

Inclusion Criteria:

• Being female and between 10 and 19 years of age
• Participating in regular volleyball training at least 3 days per week
• Having reached menarche

Exclusion Criteria:

• Having sustained a lower extremity injury within the previous 6 months
• Having a history of lower extremity surgery
• Using medication that could affect balance, attention, or physical performance
• Having a neurological, orthopedic, or systemic condition that could affect performance

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Adolescent Female Volleyball Players; Adolescent female volleyball players who were regularly training at AB Volleyball Academy and participated in this observational study. All participants completed biomechanical and functional assessments in a single session, including frontal plane knee projection angle during a single-leg squat, dynamic balance, agility, and ankle dorsiflexion mobility measurements. No intervention or experimental treatment was applied.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Frontal Plane Projection Angle	Frontal plane projection angle (FPPA) was assessed using SparkMotion software. FPPA was calculated from the angle between a line from the anterior superior iliac spine (ASIS) to the midpoint of the patella and a line from the patellar midpoint to the midpoint between the medial and lateral malleoli; this value was subtracted from 360° to obtain FPPA. Values ≥195° were descriptively classified as increased FPPA. Frontal-plane video was recorded using an iPad mounted on a tripod positioned 3 m from the participant and 1 m above the ground. Participants performed a single-leg squat with arms crossed over the chest at a metronome-paced tempo (2 s descent, 2 s ascent). FPPA was measured at the deepest squat position reached while maintaining balance. After 3 practice trials, 5 consecutive recorded squats were performed, and the third trial was used for analysis.	At a single assesment sessiomn

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Y - Balance Test	Dynamic balance was assessed using the Lower Quarter Y-Balance Test (YBT-LQ). This standardized test evaluates reach distance in the anterior, posteromedial, and posterolateral directions while maintaining single-leg stance. Reach distances were recorded to the nearest 0.5 cm using the Y Balance Test kit. Before testing, leg length was measured from the anterior superior iliac spine (ASIS) to the distal tip of the medial malleolus, and results were normalized to leg length. Participants completed 6 practice trials before testing, followed by 3 valid trials in each direction. Invalid trials were repeated, and the mean of the 3 valid trials for each direction was used for analysis. The composite score was calculated by dividing the sum of the 3 reach distances by 3 times leg length and multiplying by 100.	At a single assesment session
T - Test	Agility was assessed using the T-Test. The test course was set up in a T shape with 4 cones: cone A was positioned 9.14 m from the center cone B, and cones C and D were placed 4.57 m to the left and right of cone B. Participants started at cone A, sprinted to cone B, shuffled laterally to touch cone C, then shuffled to touch cone D, returned to cone B, and backpedaled to cone A to complete the test. Time was recorded using a photocell timing system. After 2 familiarization trials, participants performed 3 valid trials with 3 minutes of rest between trials, and the best time was used for analysis.	At a single assesment session
Weight - Bearing Lunge Test	nkle dorsiflexion mobility was assessed using the Weight-Bearing Lunge Test (WBLT). Participants were positioned facing a wall in a tandem stance, with the tested foot aligned perpendicular to the wall and the non-tested rear heel lifted. They were instructed to place their hands on the wall and move the front knee toward it while keeping the tested heel in contact with the ground. The foot was moved away from the wall in 1 cm increments until the maximum distance at which the knee could still touch the wall without heel lift was identified. The farthest valid distance between the great toe and the wall was measured in centimeters. Three valid trials were recorded for each lower extremity, and the mean value was used for analysis. Trials with heel lift, marked lower-extremity compensations, or loss of proper test position were repeated.	At a single assesment session

Collaborators and Investigators

• Sponsor: Sinop University

Publications and helpful links

General Publications

• Chalabiyev N, Basaran S, Deniz V, Adas U, Sariyildiz A. Beyond muscle activation: the role of biomechanical properties of muscles in determining dynamic knee valgus in female volleyball players. BMC Sports Sci Med Rehabil. 2026 Apr 16;18(1):249. doi: 10.1186/s13102-026-01681-1.
• Sassi LB, Miguel AC, Serafim TT, de Menezes FS, Martins TB, Okubo R. Understanding ACL injuries in volleyball: a systematic review of epidemiology and risk factors. Front Sports Act Living. 2025 Dec 8;7:1675136. doi: 10.3389/fspor.2025.1675136. eCollection 2025.

Study record dates

Study Major Dates

• Study Start (Actual): March 1, 2026
• Primary Completion (Actual): March 3, 2026
• Study Completion (Actual): July 1, 2026

Study Registration Dates

• First Submitted: July 14, 2026
• First Submitted That Met QC Criteria: July 14, 2026
• First Posted (Actual): July 17, 2026

Study Record Updates

• Last Update Posted (Actual): July 17, 2026
• Last Update Submitted That Met QC Criteria: July 14, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: dynamic balance; volleyball; agility; ankle dorsiflexion; frontal plane knee projection angle
• Other Study ID Numbers: FPPATTADF1

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