Abstract
This study aimed to investigate the hamstring flexibility rate among prepubertal soccer players from U8 to U12 and the role of age and soccer years of practice on the course of hamstring flexibility. Six hundred eleven young Italian soccer players from a local soccer school in Turin were recruited for this research and assigned to each group according to their chronological age (U8 = 124 players; U9 = 130 players; U10 = 151 players; U11 = 89 players; and U12 = 120 players). Hamstring flexibility was measured using the Sit and Reach Test (SAR), while data analysis was run using a one-way analysis of variance (one-way ANOVA). Furthermore, Tuckey’s post hoc was used to determine differences among the classes of age. Finally, a bivariate ordinal regression analysis was used to evaluate a potential association between age categories and hamstrings flexibility. In addition, multivariable ordinal regression was used to analyze this relationship adjusted for the Body Mass Index (BMI). The one-way ANOVA showed significant differences in flexibility among groups (F = 32.76, P < 0.0001). Tuckey’s post hoc identified significant differences between U8 and U10 (p < 0.01; −2,39 cm of hamstring stretching), U8 and U11 (p < 0.05; −2.19 cm), U8 and U12 (p < 0.0001; −5.90), U9 and U12 (p < 0.0001; −4.98 cm), U10 and U12 (p < 0.0001; −3.5 cm), U11 and U12 (p < 0,001; −3.70 cm). In the bivariate ordinal regression analysis, there was a negative association between the age categories and hamstrings flexibility (R2 = 0.137; p < 0.0001). The association persisted in multivariable ordinal regression analysis adjusted for BMI (R2 = 0.138; p < 0.0001). This study underlines changes in hamstring flexibility across different age groups of prepubertal soccer players. The older and more experienced in soccer are less flexible than the younger, considering the hamstring muscles. Thus, appropriate stretching protocols should be included in prepubertal soccer training to avoid the risk of lead players to excess hamstring tightness.
Highlights
“Hamstrings” is a term commonly used to refer to the muscles biceps femoris, semitendinosus, and semimembranosus, which form prominent tendons medially and laterally at the back of the knee
Hamstring flexibility training should be included in youth soccer training programs, as they tend to become tighter throughout the biological maturation, it is unclear whether this is due to physical growth or it is influenced by daily routine and practice (Zakas et al, 2002)
The bivariate regression model revealed a negative association between the age categories and hamstrings flexibility (b = −1.405, R2 = 0.137, p < 0.0001), and the association persisted if the model is adjusted for Body Mass Index (BMI) (R2 = 0.138; p < 0.0001) (Table 3)
Summary
“Hamstrings” is a term commonly used to refer to the muscles biceps femoris, semitendinosus, and semimembranosus, which form prominent tendons medially and laterally at the back of the knee. The hamstrings have a prevalence of fast-twitch fibers, and their main action is the flexion of the knee For this reason, these muscles play a crucial role in several team sports such. Even if hamstring injuries occurred at a lower incidence in youth players than adults, a study conducted among 623 young players of Barcelona Football Club revealed an incidence of damage estimate at 0.041 for biceps femoris and 0.061 for semitendinosus and semimembranosus every 1,000 h of soccer practice (Valle et al, 2018). Only a few articles investigated muscle flexibility in young soccer players (Nikolaïdis, 2012; Nikolaidis et al, 2014; Cejudo et al, 2019), and hamstrings flexibility training in youth football is a debated topic. The aim of this study is to investigate the age-related differences in hamstring flexibility in soccer school players
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