The Degree, Development and Interrelationship of Structural and Functional Asymmetry in (Pre)Adolescent Elite Tennis Players (AsymTen)

Stature (cm) Sitting height (cm) Upper- and lower extremity length (cm) body weight (kg) Body Mass Index (kg/m²) Age at Peak height Velocity (years) Skeletal muscle mass (kg)

These values will be determined every two months during a maximum period of three years, expressed as mean and standard deviation and will be used to develop growth charts and velocity curves.

Dual X-Ray Absorptiometry

• lean mass (g)
• fat mass (g)
• bone mass (g)
• total bone area (cm²)
• Bone Mineral Content (g)
• Bone Mineral Density (g/cm²)

Circumferences - upper and lower arm, thigh and calf (in cm)

Ultrasound

- Muscle thickness ((in mm) of M. Biceps, M. Triceps, M. Rectus Abdominis, Quadriceps and Hamstrings)

Bioelectric impedance

• fat (g)
• fat free mass (g)

These outcome measures will be determined on both the dominant and the non-dominant extremity/side every six months during a maximum period of three years. The side-to-side difference will be calculated using the symmetry index (see outcome measure 4). Every outcome measure described above will be expressed as mean and standard deviation for both the dominant and non-dominant extremity/side

Strength and Power:

• Seated shot put functional test (distance in cm)
• Grip Strength (kg)
• Unilateral countermovement jump (distance in cm)
• Single hop test (distance in cm)
• Medicine Ball throws (distance in cm)

Speed and Agility:

• Plate tapping (time s)
• Single leg 6-m hop test (time in s)

Balance and Flexibility:

• Upper- and Lower extremity Y-balance test (distance in cm)
• Standing On One Leg with Eyes Closed (time in s)

Motor control and Coordination:

• Unilateral hand wall toss test (score in points)
• 270 degrees tap test (time in s)

Locomotion pattern:

- Ground Reaction Forces (force in N)

Every test will be performed unilaterally for both the dominant and non-dominant extremity/side every six months during a maximum period of three years. The side-to-side difference will be calculated using the symmetry index (see outcome measure 4). The mean (plus standard deviation) of every test (dominant and non-dominant test score) will be reported

Side-to-side difference (i.e. dominant vs non-dominant extremity/side) will be calculated and expressed as a percentage (extremity symmetry index (%)) for the outcome measures described above (anthropometry, body composition and functional test battery) using following formula:

((measure dominant extremity/measure non-dominant extremity)-1) x 100

technical skill of young elite tennis players. - Technical skill performance will be examined by means of video analysis once a year and scored by an independent expert panel. Mean technical ability will be reported.

Tennis specific performance:

- Tennis players will perform the Dutch Technical-Tactical Tennis Test (D4T) once a year. The mean test score will be reported.