The main aim of this thesis was to examine hamstrings anatomy and its influence on knee flexor muscle function in healthy young men. A secondary aim was to better understand the implications of hamstrings anatomy and function, and their variability, in relation to the risk of strain injury. The functional and conventional H:Q ratios (examined up to high angular velocities) as well as the knee joint angle-specific isometric H:Q ratio exhibited good test-retest reliability at joint positions that closely replicated the conditions of high injury risk. Football players did not exhibit any differences in angle-specific or peak torque H:Q ratios compared to recreationally active controls. Knee extensor and flexor strength, relative to body mass, of footballers and controls was similar for all velocities, except concentric knee flexor strength at 400° s-1 (footballers +40%; P < 0.01). Muscle volume explained 30-71% and 38-58% of the differences between individuals in knee extensors and flexors torque respectively across a range of velocities. A moderate correlation was also found between the volume of these antagonistic muscle groups (R2= 0.41). The relative volume of the knee extensors and flexors explained ~20% of the variance in the isometric H:Q ratio and ~31% in the high velocity functional H:Q ratio. Biceps femoris long head exhibited a balanced myosin heavy chain isoform distribution (47.1% type I and 52.9 % total type II) in young healthy men, while BFlh muscle composition was not related to any measure of knee flexor maximal or explosive strength. Biceps femoris long head proximal aponeurosis area varied considerably between participants (>4-fold) and was not related to biceps femoris long head maximal anatomical cross-sectional area (r= 0.04, P= 0.83). Consequently, the aponeurosis:muscle area ratio exhibited 6-fold variability (range, 0.53 to 3.09; CV= 32.5%). Aponeurosis size was not related to isometric or eccentric knee flexion strength. The findings of this thesis suggest that the main anatomical factor that contributes to knee flexors function in vivo is hamstrings muscle size, while muscle composition and aponeurosis size do not seem to have a significant influence. The high inter-individual variability of the biceps femoris long head proximal aponeurosis size suggests that a disproportionately small aponeurosis may be a risk factor for strain injury. In contrast, biceps femoris long head muscle composition does not seem to explain the high incidence of strain injuries in this muscle. Quadriceps and hamstrings muscle size imbalances contribute to functional imbalances that may predispose to strain injury and correction of any size imbalance may be a useful injury prevention tool. Finally, regular exposure to football training and match-play does not seem to influence the balance of muscle strength around the knee joint.

This thesis examined the change in skeletal muscle architecture with contractile force production, the relationship of architecture with muscle strength parameters and if muscle tendinous tissue stiffness determines in vivo explosive strength (i.e. rate of torque development, RTD). Muscle and tendinous tissue adaptations to contrasting strength training regimes, and the potential capacity of these tissues to adapt following chronic strength training were also explored. Quadriceps femoris fascicle length (FL) decreased, while the pennation angle (PA) increased in a curvi-linearly manner from rest to maximal voluntary contraction (MVC) torque. Consequently, effective physiological cross-sectional area (effPCSA) during MVC was 27% greater than at rest, although effPCSA measured at rest and during MVC had similar correlations to maximal strength. In the earliest phase of contraction, FL, but not PA, was negatively related (R2=0.187) to voluntary RTD. Neither FL nor PA was related to maximal isometric or dynamic strength. Muscle-tendon unit (MTU) and patellar tendon (PT) stiffness were unrelated to voluntary and evoked RTD. Relative PT stiffness was also unrelated to relative RTD, although relative MTU stiffness was related to voluntary RTD (25-55%MVT, R2≤0.188) and evoked RTD (5-50%MVT, R2≤0.194). MTU stiffness increased after sustained-contraction (SCT, +21%), though not explosive-contraction strength training (ECT). PT stiffness increased similarly after ECT (+20%) and SCT (+16%), yet neither induced tendon hypertrophy. SCT produced modest muscle (+8%) and aponeurosis (+7%) hypertrophy. Chronic strength trained (CST: >3 years) males had substantially greater muscle and aponeurosis size, but similar tendon size as untrained controls (UNT) and short-term (12 weeks) strength trained (STT) individuals. Between these groups, at the highest common force, MTU stiffness was indifferent, while PT stiffness was similarly greater in STT and CST than UNT. These results suggest FL and PA have little influence on muscle strength and tendon stiffness has no influence on RTD. Maximum strength negated any qualitative influence of MTU stiffness on in vivo RTD. Component MTU tissues (muscle-aponeurosis vs. external tendon) adapt differentially depending on the strength training regime. Specifically, free tendon appeared to adapt to high magnitude loading, while loading duration is also an important stimulus for the muscle-aponeurosis. However, chronic strength training was not concordant with greater higher force MTU stiffness, and does not further increase higher force PT stiffness beyond the adaptations that occur after 12 weeks of strength training. Finally, no evidence was found for tendon hypertrophy in response to strength training.

Title: Selected parameters of postural stability in elite sport dance group. Objectives: The aim of this study is to evaluate selected parameters of postural stability in elite sport dancers in Czech Republic during their preparatory period and to define the relation of postural stability to body composition, equality and ability of explosive strength production of lower limbs. Methods: The group of 10 elite sport dancers, composed of men (n=5, age=25,1±2,4 years, height=181,9±3,8 cm, weight=73,7±7,5 kg) and women (n=5, age=24±3,2 years, height=169,1±5,7 cm, weight=53,8±3,6 kg), was longitudinally observed during their preparatory period. At the beginning and on the top (national championship) postural stability, body composition and dynamic performance were evaluated. These following devices were used for testing: force plate FootScan (RScan International, Belgium), bioimpedance analyzer BIA 2000M (Datainput, Germany) and Tanita (Tanita Corporation, Japan), dynamometric force plates Kistler 8611 (Kistler, Switzerland). Results were evaluated by descriptive and inductive (paired t-test) statistics. Results: Results showed high similarity of followed selected parameters in elite sport dancers at the beginning and also at the top of preparatory period. Postural stability was slightly impaired, but...

Muskelstärkande fysisk aktivitet kan likställas med styrketräning och definieras som fysisk aktivitet med avsikt att förbättra eller bibehålla muskulär styrka, muskelvolym och/eller muskulär uthållighet. Explosiv styrka kan beskrivas som kraftutveckling per tidsenhet och är en produkt av styrka/kraft och hastighet. Tidigare studier har visat att en god explosiv och maximal styrka bland annat kan ge hälsovinster, förbättra idrottslig förmåga, minska risken för idrottsskador och kan förebygga fallrisken hos äldre. Isometric mid-thigh pull-test (IMTP) har under de senaste 10 åren blivit ett vanligt test för att mäta helkroppsstyrka hos idrottare. Testet är lätt att administrera och har en god validitet samt reliabilitet. Studiens syfte var att undersöka sambandet mellan explosiv- och maximal styrka hos styrketränande personer vid ett IMTP-test. Tio deltagare med minst ett års erfarenhet av styrketräning rekryterades. Resultatet visade en måttligt stark korrelation (r = 0,48) mellan explosiv och maximal styrka, men ingen statistisk signifikans (p = 0,158). Deltagarnas Peak Force var i genomsnitt 2644 ± 404 N och Peak force vid 250ms var medel 1808 ± 231 N (i medel hade deltagarna uppnått 69% av Peak Force vid 250ms). Sammanfattningsvis noterades att det möjligen kan finnas en trend i korrelationen mellan explosiv och maximal styrka. Detta indikerar att maximal och explosiv styrka troligen överlappar varandra, det kan däremot inte bekräftas då det inte fanns något statistiskt samband. Vidare rekommenderas att framtida forskning undersöker explosiv styrka och maximal styrka som distinkta styrkeförmågor med fler deltagare och standardiserade testmetoder krävs för att vidare undersöka sambandet mellan maximal och explosiv styrka. / Muscle-strengthening physical activity can be equated with strength training and is defined as physical activity with the intention of improving or maintaining muscular strength, muscle volume, and/or muscular endurance. Explosive strength can be described as force development per unit of time and is a product of strength/power and speed. Previous studies have shown that good explosive and maximal strength can yield health benefits, improve athletic performance, reduce the risk of sports related injuries, and prevent the risk of falls in older adults. The Isometric Mid-Thigh-Pull-test (IMTP) has become a common test for measuring whole body strength in athletes over the past 10 years. The test is easy to administer and has good validity and reliability. The aim of the study was to investigate the relationship between explosive and maximal strength in resistance-trained individuals using an IMTP-test. Ten participants with at least one year’s experience of resistance training were recruited. The results showed a moderately strong correlation (r = 0,48) between explosive and maximal strength, but no statistical significance (p = 0,158). The participants’ Peak Force averaged 2644 ± 404 N, Peak Force at 250ms averaged 1808 ± 231 N (on average, participants had received 69% of Peak Force at 250ms). In summary, it was noted that there might be a trend in the correlation between explosive and maximal strength. This suggests that maximal and explosive strength likely overlap, but this cannot be confirmed as there was no statistical significance. Furthermore, it is recommended that future research investigates explosive strength as distinct strength abilities. More participants and standardized testing methods are required to further explore the relationship between maximal and explosive strength

Abstract available in the Journal of Strength and Conditioning Research

<p>Циљ истраживања је да се утврде ефекти 8 недеља изоинерцијалног тренинга на доминантне моторичке способности кошаркаша. Испитаници, 36 кошаркаша јуниорског узраста (17.58&plusmn;0.50 година) су подељени у 3 групе: прву експерименталну (ЕСС; n=12) која је вежбала тренинге снаге на изоинерцијалном тренажеру, другу експерименталну (CON; n=12) која је вежбала традиционални изодинамички тренинг снаге са слободним теговима, и контролну групу (KON; n=12) која није вежбала тренинге снаге. Током есперименталног програма ЕСС и CON групе су имале укупно по 12 тренинга снаге са истоветним бројем серија и понављања. На крају четврте недеље код обе експерименталне групе спроведен је тест постактивацијске потенцијације (ПАП) како би се утврдили акутни ефекти различитих метода тренинга у 4 временске тачке: 2, 4, 8 и 15 минута након вежби са оптерећењем. Резултати су показали да постоји статистички значајна разлика као последица примене различитих метода тренинга снаге у трајању од 8 недеља при чему је изоинерцијални тренинг довео до значајно бољих резултата у варијаблама скокова SJ, CMJ, VJ и у скоку са леве ноге CMJLN, затим у тесту спринта 5 m&nbsp; и тестовима агилности Т тест и 505 са окретом око десне ноге. Нису утврђене статистички значајне разлике у тестовима изометријске снаге, скока са десне ноге CMJDN, трчања 20 m и тесту агилности 505 са окретом око леве ноге. У тесту ПАП ефеката није било статистички значајне разлике у резултатима као последице различитих метода вежбања. При томе, СОN група је имала значајно побољшање у тесту скока VJ док је код ЕСС групе значајан ефекат у варијаблама скока VJ и Т тест агилности. Није било значајних ефеката ПАП у тестовима трчања 5 и 20 метара. Добијени резултати указују да изоинерцијални тренинг у трајању од 8 недеља доводи до бољих резултата у развоју експлозивне снаге, брзине и агилности младих кошаркаша у поређењу са традиционалним изодинамичким тренингом, али не и у ПАП ефектима. У складу с тим, тренери и кондициони тренери би требали да у раду са младим спортистима користе и ову методу тренинга снаге.</p> / <p>Cilj istraživanja je da se utvrde efekti 8 nedelja izoinercijalnog treninga na dominantne motoričke sposobnosti košarkaša. Ispitanici, 36 košarkaša juniorskog uzrasta (17.58&plusmn;0.50 godina) su podeljeni u 3 grupe: prvu eksperimentalnu (ESS; n=12) koja je vežbala treninge snage na izoinercijalnom trenažeru, drugu eksperimentalnu (CON; n=12) koja je vežbala tradicionalni izodinamički trening snage sa slobodnim tegovima, i kontrolnu grupu (KON; n=12) koja nije vežbala treninge snage. Tokom esperimentalnog programa ESS i CON grupe su imale ukupno po 12 treninga snage sa istovetnim brojem serija i ponavljanja. Na kraju četvrte nedelje kod obe eksperimentalne grupe sproveden je test postaktivacijske potencijacije (PAP) kako bi se utvrdili akutni efekti različitih metoda treninga u 4 vremenske tačke: 2, 4, 8 i 15 minuta nakon vežbi sa opterećenjem. Rezultati su pokazali da postoji statistički značajna razlika kao posledica primene različitih metoda treninga snage u trajanju od 8 nedelja pri čemu je izoinercijalni trening doveo do značajno boljih rezultata u varijablama skokova SJ, CMJ, VJ i u skoku sa leve noge CMJLN, zatim u testu sprinta 5 m&nbsp; i testovima agilnosti T test i 505 sa okretom oko desne noge. Nisu utvrđene statistički značajne razlike u testovima izometrijske snage, skoka sa desne noge CMJDN, trčanja 20 m i testu agilnosti 505 sa okretom oko leve noge. U testu PAP efekata nije bilo statistički značajne razlike u rezultatima kao posledice različitih metoda vežbanja. Pri tome, SON grupa je imala značajno poboljšanje u testu skoka VJ dok je kod ESS grupe značajan efekat u varijablama skoka VJ i T test agilnosti. Nije bilo značajnih efekata PAP u testovima trčanja 5 i 20 metara. Dobijeni rezultati ukazuju da izoinercijalni trening u trajanju od 8 nedelja dovodi do boljih rezultata u razvoju eksplozivne snage, brzine i agilnosti mladih košarkaša u poređenju sa tradicionalnim izodinamičkim treningom, ali ne i u PAP efektima. U skladu s tim, treneri i kondicioni treneri bi trebali da u radu sa mladim sportistima koriste i ovu metodu treninga snage.</p> / <p>The aim of this research is to determine the effects of an 8-week isoinertial training on dominant motor abilities of basketball players. Examinees, i.e. 36 junior basketball players, (17.58&plusmn;0.50 years) are divided into 3 groups: the first experimental group (ECC; n=12) which took strength training exercises on isoinertial training device, the second experimental (CON; n=12) which took traditional isodynamic strength training with free weights, and a control group (CON; n=12) which did not take any strength training exercises. During the experimental program, the ECC and CON groups had 12 strength training sessions in total including the same number of series and repetitions. At the end of the fourth week, both experimental groups were tested for post-activational potentiation (PAP) in order to determine acute effects of different training methods in 4 time points: 2, 4, 8 and 15 minutes after loading exercises. The findings indicate that there is a statistically significant difference as a result of the application of different strength training methods lasting for 8 weeks, since the isoinertial training brought about significantly better results in the variables of jumps SJ, CMJ, VJ and jump off the left foot CMJLN, as well as in the 5m sprint test and agility tests (T-test and 505 test with turn on the right leg). No statistically significat differences were found in tests of: isometric strength, jump off the right foot CMJDN, 20m run and 505 agility test with the turn on the left leg. Also, there were no statistically significant differences as a result of different exercise methods in the PAP test. In that process, CON group had significant improvement in VJ jump test, whereas in ECC group a significant effect was found in the variables of VJ and agility T-test. The 5m and 20m run tests showed no significant PAP effects either. In comparison with the traditional isodynamic training, the findings indicate that isoinertial training lasting for 8 weeks gives rise to better results in the development of explosive strength, speed and agility of young basketball players. Accordingly, coaches and trainers should use this method of strength training in work with young athletes.</p>

To assess acute performance-related effects of foam rolling, this study investigated the immediate effects of a standard foam rolling protocol on explosive strength of the plantarflexors and alpha motor neuron excitability in the soleus. Explosive strength was measured via vertical jump height (JUMP) and the Reactive Strength Index (RSI) obtained from a single leg drop jump. Alpha motor neuron excitability was measured by H reflex amplitude as H wave to M wave ratio (HM) obtained from the soleus muscle. JUMP and RSI measures were analyzed from nineteen subjects (12 male, 7 female) HM data were analyzed from 15 subjects (9 male, 6 female). Subjects attended one day of practice and instruction for the single leg drop jump and one day for data collection. One leg was randomly assigned to be the test leg (FL) and the other as the control (NL). The reported dominant leg and gender were also recorded for each subject. Subjects performed two single leg drop jumps per leg from a box height of 30 cm and then 10 soleus H reflexes were obtained. The intervention, which followed standard professional guidelines, consisted of 2.5 minutes of foam rolling for the FL and rest for the NL, followed by a 5 minute warm up on a cycle ergometer. The best jump and the average HM ratio were chosen for analysis. For each variable a post/pre ratio was calculated for statistical analysis. A 2x2x2 factor ANOVA with repeated measures on both factors was used for each variable. Analysis revealed no statistically significant differences for any of the variables, either as main effects or any of the interaction effects. Subjects trended towards a slightly larger post-intervention decrease in JUMP and RSI for the FL than the NL but this was not significant. It was concluded that a 2.5 minute intervention of foam rolling had no acute effect on explosive strength of the plantarflexors or alpha motor neuron excitability of the soleus. / text