Introduction: Soccer is a contact sport that requires high physical fitness, particularly high muscular strength. Appropriate muscular strength leads to improvement in performing technical and tactical skills and reduce injuries in this sport [1]. On the other hand, studies have shown that lower-extremity muscles play a vital role in maintaining body balance, such that optimal performance of musculoskeletal system is essential to maintain balance during exercise. Studies have also shown that a decrease in isotonic and isometric muscle strength of the lower-extremity muscles reduces balance fast recovery capability after it collapses. Since few studies have investigated the relationship between isokinetic strength of lower extremity and balance, the aim of this study was to investigate the relationship between isokinetic strength of the extensor and flexor knee muscles and test components of Biodex balance in young elite soccer players.
Methodology: Twenty-eight male soccer player of Iran’s National Team Omid with a mean±SD age of 20.39±0.68 years, height of 180.71±6.35 cm, weight of 75.05 ± 6.82 kg, BMI of 20.80±1.35 kg/m2, and without any history of lower extremity injury voluntarily participated in the present study. In order to analyze the collected data, descriptive statistical methods and Pearson Correlation Coefficient were employed at a significance level of p≤0.05.
Results: The results showed that there was no significant relationship between the peak torque of extensor and flexor knee muscles at the angular velocity of 60 degrees per second with overall balance score of respectively r=0.077, p =0.69 and r=0.201, p =0.3 and flexor/extensor ratio with the overall balance of r =0/12, p =0/5. Neither was there a significant relationship between the directions of anterior-posterior and internal-external test Biodex balance.
Discussion: Results of the present study is in agreement with the results of the studies carried out by researchers including Trapp et al. (2008) who examined the relationship between strength and balance in female college soccer players [2]. In previous studies, a significant positive correlation between muscle strength and balance in subjects with muscle weakness was observed, which dropped when the participants achieved a minimum threshold of strength [3]. Since compared to past research studies the participants of this study were elite young soccer players, the lack of relationship between strength and balance may be justifiable. It seems that further research and larger sample size are required to come up with more accurate results.