Jaroslav Teplan

ISOKINETIC STRENGTH OF KNEE FLEXORS AND EXTENSORS IN VERY YOUNG SOCCER PLAYERS

Background Monitoring of physical fitness characteristics in very young players could be helpful for the selection of talented youth or identification of the strengths and weaknesses in motor predispositions for physical performance. Muscular strength tested on an isokinetic dynamometer belongs to the most widely used methods of the identification of knee extensors (KE) and flexors (KF) strength in adult soccer players It appears that there is the lack of information concerning monitoring of isokinetic strength of lower limbs and its parameters in very young soccer players. The purpose of the study was to find out the level of isokinetic strength (IS) of KE and KF and to compare the selected characteristics of IS related to the movement velocity and limb dominancy in very young players. Methods Young players (n=16, age 8.8±0.4 years, body height=137.5±6.2 cm, body weight=30.7±4.1 kg) were tested on an isokinetic dynamometer Cybex Humac Norm. Maximum peak muscle torque (PT) of KE and KF, their mutual ratio (H:Q) and bilateral ratio between Q:Q or H:H were assessed during concentric contraction at different velocities (60,180,300°.s-1) in the dominant leg (DL) and non-dominant leg (NL). Mixed-design ANOVA was used for evaluation of PT differences between the factors (angular velocity, limb dominancy, muscle groups–KE, KF). For multiple comparisons we used Bonferonnis post-hoc test. Statistical significance was set at p≤0.05. Effect size was assessed using the ηp2 coefficient. Results The results of PT during 60,180 and 300°.s-1 were (KE [DL]: 60.9±11.6, 39.2±7.3, 30.9±5.4 N•m, [NL]: 60.8±12.2, 41.1±7.8, 33.6±6.3 N•m and for KF [DL]: 34.5±6.2, 24.5±4.1, 19.7±4.3 N•m, [NL]: 33.2±5.7, 24.6±5.8, 20.0±4.8 N•m). Movement velocity had a significant effect on the level of PT (peak torque) in the players F(1.3, 77.9)=414.9, p<0.01, ηp2=0.874 and HQ ratio (F(1.7, 49.8)=7.6, p<0.01, ηp2=0.202. With increasing velocity, significant differences were revealed in PT (L vs M, L vs H, M vs. H p<0.01) and HQ ratio (L vs M, L vs H p <0.05). Limb dominancy did not significantly influence the level of PT F(1, 60)=0.180, p>0.05, ηp2=0.687 or H:Q F(1, 30)=0.760, p>0.05, ηp2=0.025. Movement velocity and limb dominancy did not have any significant effect on the bilateral ratio between QQ and HH in young soccer players (p>0.05). Conclusion The results indicated significant differences in PT and HQ in relation to movement velocity. On the contrary, no significant differences were found in bilateral ratio (Q:Q, H:Q). Limb dominancy did not significantly affect any of the observed characteristics. The presented data may contribute to comparison or establishment of standards for strength profile in this age category. Supported by GAČR P407/11/ P704 and MSM 0021620864.

ELITE SOCCER'S LOWER LIMBS EXPLOSIVE STRENGTH ASYMMETRY

Background A vertical jump is one of essential motor skills in many sports (Vanezis & Lees, 2005). Monitoring and description of vertical jumps is based on both external movement structure and explosive strength of lower limbs as a basic driving impulse for its performance. Explosive strength is one of the most important components for the body increasing and vertical jump (Aragon, 2000). Methods The research group consisted of elite soccer players (n=138, age=25,1±4,7 years, height=184,2±7,2 cm, weight=79,7±8,1 kg). For recording force effect of lower limbs on the surface, two force platforms Kistler B8611A (KISTLER Instrumente AG, Switzerland) were used. All participants performed three types of a vertical jump, T1–countermovement jump with arms included, T2–countermovement jump with arms excluded, T3–squat jump. Evaluation parameters were: high of the jump (cm), maximal strength produced by separate lower limb FmaxR(L) and strength impulse produced by separate lower limb during the take off (Ns-1). Results The heights of the jumps were CMJ-FA=42.83±4.88 cm, CMJ=37.55±4.18 cm a SQJ=35.97±3.97cm. Maximal strength produced by separate lower limb was recalculated by dividing to weight of every player as a strength for one kilogram; FmaxPT1=1.32±0.11 N.kg-1 resp. FmaxLT1=1.27±0.11 N.kg-1; FmaxPT2=1.33±0.14 N.kg-1 resp. FmaxPT2=1.28±0.16 N.kg-1; FmaxPT3=1.12±0.12 N.kg-1 resp. FmaxLT3= 1.09±0.09 N.kg-1. The level of asymmetry was evaluated by percentage difference between maximal strength of right or left lower limb per one kilogram of boy weight. Percentage difference between maximal strength was T1=5.86±4.58%; T2=9.61±7.92, T3=5.47±6.49%. Evaluation of lower limbs asymmetry by help of strength impulse using the take off was T1=9.91±10.49 N.s-1, T2=8.55±7.34 N.s-1, T3=5.69±4.73 N.s-1. Discussion/Conclusions The best results were achieved in the first type of the vertical jump (T1). Results of the countermovement jump without arm swing (T2) and squat jump without arm swing (T3) are more comparable, although it could be expected that squat position could improve the height of absolute value of the vertical jump. The biggest asymmetry by maximal strength point of view was found in the jump T2. Jumps T1 and T2 had asymmetry by maximal strength point on were similar and the absolute value was only half according to jump T1 asymmetry. The biggest asymmetry by strength impulse was in the jump T1, rest jumps aszmmetry were lower (T2-13%; T3-42%). Project was supported: MSM 0021620864, GACR P407/11/P784, PRVOUK 38.

Úroveň aerobní kapacity elitního dorosteneckého týmu a profesionálního seniorského týmu na začátku přípravného období ve fotbale

Cilem teto studie bylo zjistěni a porovnani aktualniho stavu aerobni kapacity mezi profesionalnim seniorským týmem a věkově nejstarsim elitnim dorosteneckým týmem na zacatku připravneho obdobi ve fotbale. Kategorie seniorských hraců byla tvořena 17 hraci (věk: 23,5 ± 3,2 let, tělesna hmotnost: 76,5 ± 4,2 kg, tělesna výska: 183,3 ± 3,2 cm, BMI: 22,8 ± 0,7 kg.cm -2 ) a kategorii U19 tvořilo 14 hraců (věk: 18,3 ± 0,2 let, tělesna hmotnost: 74,9 ± 6,5 kg, tělesna výska: 181,5 ± 6,3 a BMI: 22,8 ± 0,6 kg.cm -2 ). K monitorovani a hodnoceni aerobnich parametrů byl použit Yo-Yo intermitentni recovery test 1 (Yo-Yo IRT1). Na zakladě celkove uběhnute vzdalenosti a parametru VO2max byl výsledek při porovnani rozdilů průměrů sledovaných skupin statisticky významný. Parametry SFmax a pokles SF za 1 minutu nebyly signifikantně významne. Přechod z dorostenecke do seniorske kategorie zvysuje naroky na rychlost v utkani ci provaděni individualnich hernich cinnosti. Vsechny zjisťovane parametry těchto kategorii jsou pouze předpokladem pro vrcholový výkon v utkani.