Expression and assessment of maximal muscle power in relation to the characterics of external load and training history

Sposobnost ispoljavanja maksimalne snage (Pmax) mišića kod ljudi predstavlja osnovu za efikasno realizovanje važnih kretnih zadataka u sportu, na poslu, i u svakodnevnim aktivnostima. Ipak, dobro je poznato da veliki broj faktora utiče ne samo na ispoljavanje, nego i na procenu Pmax mišića. Uprkos tome, evidentan je znatan broj nekonzistentnosti u dosadašnjim nalazima, ali i neispitanih uticaja za pojedine faktore. S tim u vezi, postavljeno je više ciljeva koji su se odnosili na ispoljavanje i procenu Pmax mišića vezanih za dva potencijalno važna faktora: karakteristike spoljašnjeg opterećenja i utreniranost. Konkretno, ciljevi su bili da se: (i) ispita pri kom se intenzitetu opterećenja ispoljava Pmax mišića u vertikalnim skokovima; (ii) ispita uticaj utreniranosti na ispoljavanje Pmax mišića u vertikalnim skokovima; (iii) ispita uticaj tipa opterećenja na ispoljavanje Pmax mišića u vertikalnim skokovima; (iv) ispita pri kome se intenzitetu opterećenja ispoljava Pmax mišića u zadatku maksimalnog sprinta na bicikl ergometru; (v) ispita uticaj utreniranosti na optimalno opterećenje (OOPT) pri kome se ispoljava Pmax mišića u zadatku maksimalnog sprinta na bicikl ergometru; i (vi) utvrdi i evaluira regresioni model za predikciju OOPT za ispoljavanje i procenu Pmax mišića u zadatku maksimalnog sprinta na bicikl ergometru. U eksperiment je bilo uključeno četrdeset odraslih muških ispitanika, koji su bili razvrstani u četiri grupe u odnosu na tip i nivo utreniranosti: Jaki (individualci trenirani po tipu jačine, n = 10), Brzi (individualci trenirani po tipu brzine, n = 10), Aktivni (fizički aktivni individualci nesportisti, n = 10) i Neaktivni (fizički neaktivni individualci nesportisti, n = 10). Karakteristike uzorka su ocenjene na osnovu uzrasta, visine tela, mase tela (MT), procenta masnog tkiva, i jačine mišića nogu u testu Jedan ponavljajući maksimum iz polučučnja (1PMPČ). Maksimalna snaga mišića nogu se procenjivala u sledećim testovima: Vertikalni skok (VS), Vertikalni skok iz polučučnja (VSPČ) i Vingejt anaerobni test – 6 sekundi maksimalnog sprinta (VAnT6s). Merenja koja su uključila dve varijante vertikalnog skoka sprovedena su posebno za dva tipa spoljašnjeg opterećenja. Konkretno, u prvom slučaju manipulacija spoljašnjim opterećenjem se vršila simulacijom delovanja konstantne spoljne sile, čime se kao komponenta opterećenja menjala samo težina (T), što je izvršeno uz pomoć specijalno konstruisanog sistema za opterećenje i rasterećenje. Za ovaj tip opterećenja ukupno je primenjeno sedam intenziteta opterećenja (interval od 0.7 do 1.3 T tela). U drugom ix slučaju se, uz manipulaciju sa T omogućila i promena delovanja inercije (I). Dakle, manipulacija intenzitetom se vršila preko obe komponente opterećenja, T i I (T+I), za šta je korišćen specijalni prsluk sa opterećenjem. Za ovaj tip opterećenja je primenjeno ukupno četiri inteziteta opterećenja (interval od 1.0 do 1.3 T+I tela). Merenja na bicikl ergometru u VAnT6s su obuhvatila osam intenziteta opterećenja (interval od 5 do 12% MT). Podaci dobijeni u realizovanom istraživanju obrađeni su primenom deskriptivne, komparativne i regresione statističke analize...The ability to express maximum muscle power (Pmax) in humans represents the basis for the efficient realization of the important movement tasks in sports, at work, and in everyday activities. However, it is well known that numerus factors affect not only the expression, but also an assessment of Pmax. Nevertheless, there is a substantial number of apparent inconsistencies in previous findings, as well as underexplored influences of certain factors. In this regard, there were several aims that have been related to the expression and assessment of Pmax in relation to the role of two potentially important factors: the characteristics of the external load and training history. Specifically, the objectives were to: (i) examine which the intensity of the load ensure production of Pmax in vertical jumps, (ii) examine the effect of training history on the expression of Pmax in vertical jumps; (iii) examine the effect type of load on the expression of Pmax in vertical jumps, (iv) examine which the intensity of the load allows for production of Pmax in the task of maximum sprint on a bicycle ergometer; (v) explore the effect of training history on the optimum load (LOPT) for production of the Pmax in the maximum sprint on a bicycle ergometer task, and (vi) determine and evaluate the regression model for the prediction of LOPT for expression and assessment of Pmax in the maximum sprint on a bicycle ergometer task. Forty adult male subjects participated in the experiment. They were divided into four groups based on their type and level of training history: Strength (strength-trained athletes, n = 10), Speed (speed-trained athletes, n = 10), Active (physically active non-athletes, n = 10) and Inactive (physically inactive non-athletes, n = 10). Subjects characteristics were assessed on the basis of age, body height, body weight (BW), percentage of body fat, and muscle strength in the One repetition maximum from half squat (1RMHS) test. Maximum muscle power was estimated by the following standard tests: Countermovement jump (CMJ), Squat jump (SJ), and the Wingate anaerobic test – 6 second maximal cycling sprint test (VAnT6s). The maximum vertical jumps tests (CMJ and SJ) were performed separately for the two types of external load. Specifically, in the first case, based on specially designed a pulley system for loading and unloading, the manipulation of the external load was conducted by simulating effects of constant external force, whereby only the weight (W) has been changed as a component of the load. For this type of load seven different intensities (interval from 0.7 to xii 1.3 W of body) were applied. In the second case, a special weight vest was used for the manipulation of the external load through the both components, weight and inertia (W+I). For this type four different intensities (interval from 1.0 to 1.3 W+I of body) were applied. Finally, eight load intensities (interval of 5 to 12% of BW) were included in test performed on a bicycle ergometer in VAnT6s. Data obtained in the study were analyzed using descriptive, comparative and regression statistical analysis..

Analysis of training load and performance in designing smart bodyweight power training: effects of set structure in vertical jumping sessions

The purpose of this study was to investigate the role of set structures in designing bodyweight power training (BWPT). Specifically, we compared the effects of the cluster set structure undulating variant (CSSUV) and the traditional set structure (TSS) on training load and performance during vertical jumping sessions. Sixteen active males participated in this study. We designed four training sessions that consisted of 144 countermovement jumps distributed into 12 sets, where the number of repetitions varied for the CSSUV sessions, whereas for TSS sessions the number of repetitions was fixed. In addition, both of the applied set structures included sessions with short (60 seconds) and long rest periods (120 seconds), while training volume was separately analysed for the first six sets (small volume) and the last six sets (large volume). External load, internal load, and performance variables were calculated. The results suggest that CSSUV allows superior utilization of applied external load, reduction of internal load and overall higher performances that are maintained during entire training session compared to TSS (p<.05). The present study provides important findings about advantages of CSSUV over TSS in terms of external load, internal load, and performances during vertical jumping sessions, and therefore, it might be more suitable approach to designing BWPT

Pouzdanost modifikovanog kliničkog testa uticaja senzornih interakcija na posturalnu stabilnost sportista uzrasta od 10 do 12 godina

Based on the literature, reports about bilateral stance assessments based on force plate measurements in elementary schoolchildren and athletes are limited. The present study was designed to report reliability values for postural stability in 10 to 12 years old athletes using the Balance Master system. Twenty young athletes who regularly practice their sport activities at least three times per week, participated in the reproducibility study (mean age 11.4±1.0). The modified clinical test of sensory interaction on balance (mCT­SIB) quantified children's static standing balance. Intraclass correlation and Cronbach's alpha coefficients for three repeated measures reliability of the four sensory conditions of the mCTSIB showed good to excellent reliability, ranged between 0.772 and 0.949. Reproducibility was assessed with one way ANOVA with replication and non statistical differences among three measurements were recorded. Based on the obtained findings, it could be concluded that applied tests can be used in reliable assessment of standing balance in 10 to 12 age athletes. .Kratak naslov: Statička posturalna stabilnost sportista uzrasta od 10 do 12 godina. Na osnovu pregleda literature, može se zaključiti da o primeni kompjuterizovane posturografije u proceni posturalnog statusa dece i sportista nema dovoljno podataka. Zbog toga je osmišljeno istraživanje kojim je ispitana pouzdanost testa za procenu posturalnog statusa sportista uzrasta 10 do 12 godina, pri­menom kompjuterizovane posturografije. U istraživanju je učestvovalo 40 dečaka starosti 11,4 (±1.0) godina, koji se aktivno (bar tri puta nedeljno) bave nekim sportom. Za procenu sposobnosti održavanja posturalne stabilnosti, korišćen je tzv. modifikovani klinički test uticaja senzornih informacija na ravnotežu. Intraklas korelacioni koeficijent i krombah alfa koeficijent za tri ponovljena merenja bili su u intervalu od 0,772 do 0,949. Ponovljivost testa proveravana je jednofaktorskom analizom varijanse sa ponavljanjem za tri uzastopna merenja i nisu dobijene statistički značajne razlike. Dobijeni rezultati ukazuju da su evaluirani testovi za procenu posturalne stabilnosti pouzdani, te se mogu koristiti u proceni ravnoteže kod sportista uzrasta od 10 do 12 godina

SPEED-ACCURACY TRADEOFF OF INSTEP KICK IN YOUNG SOCCER PLAYERS

The speed-accuracy trade-off of fast movements acts inversely and as such is known as the Fitts's law. The aim of this study is to determine how instep kick (IK) speed grading instructions affect the instep kick speed and accuracy. The primary hypothesis assumes that a complex motor task such as IK has an inverse relation between speed and accuracy, and the secondary hypothesis assumes that the applied speed grading instructions are sensitive. The research involved 13 male players, the average age of 15 years (±1.6). The experimental protocol included the execution of IK at five different speeds, determined by verbal instructions to respondents. For assessment of kicking accuracy, we observed the following dependent variables: mean radial error (MRE), bivariate variable error (BVE), and centroid radial error (CRE). Comparative analysis has shown that higher accuracy (reduced MRE) and kicking consistency (reduced BVE) are achieved under lower kicking speeds, but these effects were not achieved in regard to CRE. Subsequent analyses have shown that MRE has a tendency towards a significant difference between the slowest and fastest kicks (p=0.068-0.075), while in the case of BVE it has been found that there are differences between the slowest and all other speed levels (p≤0.05). The main findings of this study have indicated a partial existence (two of three variables) of an inverse relationship between speed and accuracy in complex motor tasks such as IK (multi-joint and discrete motion)

The effects of different vertical jump height on electromyographic, kinematic and kinetic variables

Countermovement jump (CMJ) is an element of many sports techniques and has an important role in the overall performance, both when performed at maximal and submaximal intensity. This paper aims to investigate changes in biomechanical and neuromuscular variables that are responsible for controlling different submaximal intensities of the CMJ. 8 healthy and uninjured volleyball players from the first league of the Republic of Serbia, average age 21.9 ± 1.9 years, average body height 191.6 ± 9.2 cm, average body weight 83.1 ± 7.1 kg were included in the study. Subjects performed CMJ at three different jump heights (approximately 65%, 80%, and 95% of the maximal height). For the analysis of electromyographic data, the value of root mean square analysis was used separately for the amortization phase and the jump phase, for the following muscles: m. gluteus maximus (GlutM), m. rectus femoris (RF), m. biceps femoris (BF), m. vastus lateralis (VL), m. tibialis anterior (TA) and m. gastrocnemius medialis(GastM).Kinematic and kinetic variableswere monitored: vertical center of mass displacement in the amortization phase [m], the center of mass height at take-off point [m], jump height [m], jump speed [m/s], angular displacement in the ankle, knee and hip joint [rad], maximal vertical ground reaction force [N/ kg], vertical stiffness [kN/m/kg], the torque of the ankle, knee and hip joint [Nm/kg]. The change in jump height (65, 80 and 95%) did not have a significant effect on the change in activation for most muscles (p≥0.05), except for GastM where a tendency towards increase was observed (p=0.066). During jump phase, the activation of VL, BF, GlutM, TA muscles significantly increased compared to the amortization phase (p≤0.05). The torque in the hip joint increased significantly with increasing jump height (65<80=95%) (p=0.028). During amortization phase, the values of vertical center of mass displacement increased significantl y between each jump height (65<80<95%) (p≤0.05), while the values of vertical stiffness decreased with increasing jump height, where significant differences were observed between 80% and 95% of maximal jump height (65=80<95%) (p=0.012). Angular displacements in the knee and hip joint increased significantly with increasing jump height (65<80<95%) (p≤0.05) while no changes in angular displacement in the ankle joint were observed (p≥0.05). The results of the research show that the increase in the jump height is related to an increase in the amortization phase, due to an increase in angular displacements in the knee and hip joint, as well as an increase in torque of the hip joint