Unilateral and Ipsilateral Strength Asymmetries in Elite Youth Soccer Players With Respect to Muscle Group and Limb Dominance

Abstract

The purpose of study was to identify the presence of strength asymmetries (SA) in young elite soccer players in relation to muscle group (knee extensors (KE) and flexors (KF)) and limb preference (dominant vs. non-dominant limb). Forty-one U16 national team soccer players (mean age 15.7±0.3 years, body height 177.9±6.6 cm, body weight 68.2±7.9 kg) participated in this study. Assessments were performed on a Cybex Humac Norm isokinetic dynamometer in concentric contraction. We noted the degree of SAs in the bilateral ratio of quadriceps and hamstrings and in the ipsilateral ratio of the dominant (DL) and non-dominant (NL) legs. Bilateral deficits of KFs were higher (9.02-12.61 %) than those of KFs (6.32-7.15 %). The percentage of SA (>10 %) in knee extensors was 19.5-31.7 %. The percentage of SA (>10 %) in knee flexors was 36.6-51.2 %. At the lowest velocity, there was a significantly higher prevalence of SAs in KFs than in KEs (χ 2 = 4.11, p.05). The results of the study suggest that more than 73.2 % of players have at least one SA. More attention should be paid to knee flexors, where a higher percentage of strength asymmetries were observed; furthermore, a higher percentage of strength asymmetry was seen in the non-dominant lower limb.