Tomáš Gryc

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.

Performance and Kinematic Differences in Putting Between Healthy and Disabled Elite Golfers

Abstract Golfers with disability are limited in the execution of the full golf swing, but their performance in putting may be comparable because this stroke does not demand significant strength, balance and range of motion. Therefore, the aim of this study was to compare putting performance, kinetic and kinematic consistency between golfers with different disabilities and healthy athletes. The participants consisted of three disabled athletes (perinatal cerebral palsy, multiple sclerosis, below knee lower limb amputee) and three healthy golfers (age 34 ± 4.5 years, body height 178 ± 3.3 cm, body mass 83 ± 6.2 kg). The golfers’ movements were recorded by active 3D markers for kinematic analyses; the subjects performed 10 trials of a 6 m putting task while standing on separate force platforms placed under each lower limb. Putting performance was measured by the distance of the final ball position to the centre of the hole. ANOVA analyses did not show any differences in clubhead speed and total ball distance from the hole. The consistency of those two parameters expressed by the coefficient of variation (CV) was CV = 0.5% or better in both groups for clubhead speed and ranged from CV = 0.40 to 0.61% in healthy and CV = 0.21 to 0.55% in disabled athletes for total error distance. The main effect ANOVA showed differences in weight shift, hip and shoulder kinematics (p < 0.05) between healthy players and all players with disability. All disabled athletes shifted their weight toward the healthy side (towards the healthy lower limb) and alternated the end of the swing. The player with below knee amputation had the lowest range of motion in the shoulder joint during the putting stroke. The players with perinatal cerebral palsy and multiple sclerosis had the largest range of motion in the hips. Putting performance of disabled golfers was similar to healthy athletes. During training of disabled players, coaches should pay attention to the specificity of a particular disability when focused on putting performance. However, individual technique should achieve the same consistency as observed in healthy players.

Foot typology, body weight distribution, and postural stability of adolescent elite soccer players: A 3-year longitudinal study

Objective The unique foot morphology and distinctive functions facilitate complex tasks and strategies such as standing, walking, and running. In those weight-bearing activities, postural stability (PS) plays an important role. Correlations among foot type, PS, and other musculoskeletal problems that increase sport injury risk are known. However, long-term associations among the foot type, the PS, and body weight (BW) distribution are lacking. Thus, the purpose of this study was to longitudinally identify changes in foot morphology, PS, and symmetry in BW distribution during adolescence among elite male soccer players. Methods Thirty-five Czech elite male soccer players (age, 15.49 ± 0.61 years; BW, 64.11 ± 6.16 kg; body height, 174.62 ± 5.71 cm) underwent foot type, PS, and BW distribution measurements during 3 consecutive years (T1, T2, T3). The Chippaux-Smirak index (CSI), BW distribution, and centre of pressure (COP) displacement (total traveled way [TTW]) of each player for the preferred (PL) and non-preferred leg (NL) were acquired. Repeated-measures analysis of variance (RM ANOVA), Bonferroni´s post hoc tests, and partial eta-squared (ηp2) coefficient were used for investigating the effect of time on selected variables and effect size evaluation. Results Statistically significant effect of time on CSI values (PL: F2,68 = 5.08, p < 0.01, ηp2 = 0.13 and NL: F2,68 = 10.87, p < 0.01, ηp2 = 0.24) and COP displacement values (PL: F2,68 = 5.07, p <0.01, ηp2 = 0.13; NL: F2,68 = 3.53, p <0.05, ηp2 = 0.09) for both legs over 3-years period was identified. Furthermore, the Bonferroni´s post hoc analysis revealed a significant improvement of PS values in the PL (TTWT1 = 1617.11 ± 520.22 mm vs. TTWT2 = 1405.29 ± 462.76, p < 0.05; and between TTWT1 = 1617.11 ± 520.22 mm vs. TTWT3 = 1370.46 ± 373.94, p < 0.05). Only BW distribution parameter showed no significant differences, although slightly improved over time. Conclusions We observed changes in foot typology, PS, and BW distribution in young elite male soccer players during 3 consecutive years. Results demonstrated that changes in PS and body weight distribution under the high-load sport conditions during adolescence may improve with aging, except for foot morphology. Therefore, foot morphology should be carefully monitored to minimize sport injury risk in professional young soccer players during adolescence. Further research is necessary to determine more clear associations between these parameters, soccer-related injuries, and sport performances.

Rotace horní části těla při golfovém švihu u elitních hráčů

Při golfovem svihu se zapojuji vsechny tělni segmenty a je tak považovan za jeden z nejkomplexnějsich pohybů ve sportu. Cilem studie bylo urcit u zvolených kinematických parametrů pohybu panve a segmentů horni casti těla (rotace ramen, rotace boků, X-faktor, nataženi X-faktoru), ktere ovlivňuji rychlost hlavy hole při kontaktu s mickem u elitnich hraců golfu. Pro utvořeni modelu horni casti těla bylo použito sest aktivnich bodů a jejich poloha v průběhu měřeni byla snimana 3D kinematickým analyzatorem CODA Motion System. Pro urceni stability provedeni byl použit variacni koeficient a pro statisticke hodnoceni vztahu mezi kinematickými a casovými parametry a rychlosti hlavy hole při kontaktu s mickem byl použit Pearsonův korelacni koeficient. Byla zjistěna vysoka interindividualni stabilita provedeni, předevsim u parametrů maximalni rotace ramen v napřahu a rychlost hlavy hole v okamžiku kontaktu s micem. Při vztahove analýze mezi rychlosti hlavy hole v okamžiku kontaktu s mickem a sledovanými kinematickými parametry pohybu horni casti těla byl nalezen vysoký vztah pouze s parametrem nataženi X-faktoru.