Isokinetic strength of knee flexors and extensors of adolescent soccer players and its changes based on movement speed and age

Abstract

BACKGROUND: During childhood and adolescence there is growth in muscle strength. The dynamics of change in muscle strength and its causes have not yet been fully clarifi ed and may diff er within individuals and specifi c groups. The knowledge of current isokinetic strength levels among athletes of varying ages and disciplines represents important information from the point of view of sport performance, as well as health prevention.OBJECTIVE: The aim of this study is to determine within a group of highly trained adolescent soccer players (n = 45; age = 17 ± 1.2 years; body height 178.4 ± 5.3 cm, body weight 68.5 ± 7.6 kg) the isokinetic strength of knee fl exors and extensors and to judge whether it is signifi cantly infl uenced by age and movement speed.METHODS: A group of players was further divided according to age into 3 subgroups -U16 (n = 16); U17 (n = 14); U18 (n = 15). . The parameter evaluated was the isokinetic peak torque (PT; Nm). RESULTS:The ANOVA results demonstrate that there was a signifi cant decrease in the PT within the entire group of players with an increase in speed during both fl exion and extension (dominant extremity: p < 0.001 resp. p < 0.019; non-dominant extremity: p < 0.001; resp. p < 0.001). The diff erence in PT among the age categories was not significant for both fl exors and extensors at the speed of 60° × s -1 (p = 0.005; resp. p = 0.036) and the speed of 180° × s -1 (p = 0.036; resp. p = 0.033). However, signifi cant diff erences in PT among individual categories were confi rmed only in some cases and, by contrast, an insignifi cant decrease was marked with nondominant leg extensors. CONCLUSIONS:The results of this study indicated the state of the strength readiness of the highly trained soccer players in the junior category and the potential shortcomings in the concept of strength preparation within a leading club in the Czech Republic. These results contributed to the deepening of knowledge about changes in strength with age and confi rmed the importance of applying diagnostics during systematic long-term sport preparation.

Hip abductors and thigh muscles strength ratios and their relation to electromyography amplitude during split squat and walking lunge exercises

“…This might be similar effect to HAB/Q, where stronger Gmed might decrease the demand for VM activity. Subjects involved in this study did not have hip abduction, quadriceps or hamstring weakness itself (referenced in Table 1) according to normality data (Bohannon, 1997;Buchanan & Vardaxis, 2009;Danneskiold-Samsoe et al, 2009;Harbo, Brincks, & Andersen, 2012;Lehnert, Urban, Procházka, & Psotta, 2011), so the possibility that higher muscle activity would be find due to its weakness or malfunction was rejected.…”

“…A limitation of this study is the EMG response for selected load of 5RM, which can vary between the individuals due to the genetic profile (Petr et al, 2014) or type of exercise (Čoh & Žvan, 2011). Although H/Q ratio has already been standardized in general population (Danneskiold-Samsøe et al, 2009;Harbo et al, 2012) and athletes (Lehnert et al, 2011;Maly, Figure 2. Analysis of variance: differences between groups.…”

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“…On the other hand, some individuals showed a large increase in maximum strength (up to 56Nm), which is typical for novices at the beginning of a strength training program. When comparing these results, differences in the isokinetic machines and testing procedures, as well as some details such as the use of verbal and visual feedback or comfort in the test body position have to be considered (Lehnert, Urban, Procházka, & Psotta, 2011). The isometry test was performed unilaterally, where there was no change in the bilateral strength deficit as in previous studies Maly, Zahalka, Mala, & Cech, 2014).…”

Pre-Season Bilateral Strength Asymmetries of Professional Soccer Players and Relationship with Non-Contact Injury of Lower Limb in the Season

“…Other studies agree on similar conclusions. In the analysis of the young soccer players, no meaningful correlations in the asymmetry of the knee extensors have been proved (Lehnert, Urban, Procházka, & Psotta, 2011;Silva, Nassis, & Rebelo, 2015;Forbes et al, 2009). These results are confirmed by further research by professional players (Teixeira, Carvalho, Moreira, Carneiro, & Santos, 2015;Zabka, Valente, & Pacheco, 2011;Zakas, 2006, Daneshjoo et al, 2013Rahnama, Lees, & Bambaecichi 2005;Eniseler, Şahan, Vurgun, & Mavi, 2012).…”