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Main authors: Fernando Domínguez-Navarro, Javier Gámez-Payá, Borja Ricart-Luna e Iván Chulvi-Medrano
In basketball, jumps, sprints, changes of direction are constant. Most of these are performed unilaterally: one leg supporting the movement, one leg propelling the body more, a preference for one side. This can lead to what are known as inter-limb asymmetries (performance differences between one leg and the other).
For years, it has been suggested that when these asymmetries exceed 10–15%, they affect athletic performance and even increase the risk of injury. But is this really true in the case of elite youth basketball?
A recent study with 320 players from Valencia Basket, aged between 14 and 18, has analyzed whether these asymmetries influence speed, agility and jumping ability.
Plan of the study
To measure asymmetries, the unilateral Countermovement Jump (CMJ) was used, one of the most reliable tests for assessing explosive force and muscle imbalances.
The athletes were classified into three groups according to their asymmetry index (AII):
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Low: 0–9.9%
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Moderate: 10–14.9%
- High: >15%
Subsequently, three key basketball performance variables were evaluated:
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14-meter and 28-meter sprints (half court and full court).
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Cone Drill agility test.
- Vertical jump (bilateral and unilateral countermovement jump).
Key findings
- Common asymmetries. The average asymmetry was 10.6%, and around 40% of the players presented values above 10%
- No impact on the performance. No significant differences were found in sprinting, agility, or jumping ability between players with more or less asymmetries.
- The 10–15% threshold is questioned. This range, considered “critical” in sports like soccer, does not appear to have the same relevance in youth basketball.
- Leg dominance ≠ performance. The dominant leg was not always the strongest; it only showed influence in some unilateral jumps.
What does this mean for coaches and physical trainers?
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Don´t obsess over the 10-15%. In young basketball players, having asymmetries of this level does not necessarily imply worse performance.
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Key sport context. Every sport has different demands: What is critical in soccer many not be in basketball.
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Longitudinal monitoring. Since young people are still growing, asymmetries can change overtime and it should not be interpreted in isolation.
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Functional assessment. Rather than focusing solely on the number, it is important to observe how the asymmetry is transferred to the court and to specific games movements.
Conclusion: Low performance is not the result of asymmetry
This study challenges the belief that overcoming 10-15% leg asymmetry impairs performance in young basketball players. Although asymmetries are frequent, they do not appear to negatively affect speed, agility or jump ability.
The key is to understand them as a part of the process of development and adoption to sport, rather than as a problem to be corrected immediately.
These results are part of the research of the Basketball Chair, L’Alqueria – Universitat de València, whose aim is to provide scientific evidence to improve the performance and health of the young athletes.
