Identifying Relevant Countermovement-Jump Parameters for Academy Soccer Players.

Area of Science:

• Sports Science
• Biomechanics
• Talent Identification

Background:

• The bilateral countermovement jump (CMJ) is a key performance indicator in soccer.
• Assessing the reliability and relevance of CMJ parameters is crucial for talent identification and athlete monitoring in academy soccer players.

Purpose of the Study:

• To determine the test-retest reliability and relevance of various bilateral countermovement jump force-time parameters.
• To identify the most reliable CMJ variables for use with academy soccer players.

Main Methods:

• Sixty-three academy soccer players performed bilateral CMJ tests using dual force plates.
• Test-retest reliability was assessed on a subset of 20 players over two sessions.
• Principal-component analysis was used to reduce data dimensionality and identify key underlying factors.

Main Results:

• Most outcome-based and time-based CMJ variables exhibited acceptable to excellent reliability (ICC ≥ .67).
• Symmetry-based variables demonstrated superior reliability (ICC ≥ .90) compared to asymmetry-based variables (ICC ≥ .11).
• Principal-component analysis identified distinct components for outcome, time, and symmetry/asymmetry variables, explaining substantial variance.

Conclusions:

• Selected bilateral CMJ parameters are reliable for academy soccer players.
• Symmetry-based CMJ variables are recommended over asymmetry-based variables due to their higher reliability.
• These findings support the use of specific CMJ metrics for performance assessment in young soccer athletes.