Relationship between knee extensor muscle strength and movement performance: the effect of load and body size

The main aim of the present study was to evaluate the effect of external loading on the relationship between leg muscle strength and vertical jump performance. Sixty-six physically active men performed maximal countermovement jumps (CMJ) under five loading conditions: body weight (BW), negative loads (85% BW and 70% BW) and positive loads (115% BW and 130% BW), on a force plate. CMJ was followed by the measurement of subjects’ maximal concentric knee extension torque at 60ºs-1 by an isokinetic dynamometer. The relationship between knee extensor strength and jumping performance with various loads was assessed by Pearson’s correlation coefficients and partial correlation coefficients after controlling for body mass. Knee extensor muscle strength correlated significantly (r=.78-.79; all p<.01) with peak power output during CMJ under all loading conditions. Considerably lower correlation coefficients (r=.18-.43; p=.01-.15) were observed between knee extensor strength and CMJ height under all loading conditions, which tended to be higher after the effect of body mass had been removed (r=.37-.51; all p<.01). These results contradict the general belief that an increase in external load is associated with the increased role of leg muscle strength in maximizing power output and jump height. Furthermore, the results suggest that relative strength is a better predictor of jumping performance than absolute strength, independently of external loads used

Osnove trreninga s otporom

Treningu s otporom u posljednjih dvadesetak godina znatno raste popularnost. To je oblik tjelesne aktivnosti koji se tradicionalno percipirao kao sastavni dio programa treninga ograničenih na vrhunske sportaše, bodybuildere i dizače utega koji nastoje poboljšati svoje izvedbe. Međutim, ta koncepcija više nije istinita. Opsežna istraživanja otkrivaju da je trening s otporom ne samo učinkovita metoda za poboljšanje mišićne izdržljivosti, jakosti i snage, nego i za poboljšanje zdravstvenog stanja većine pojedinaca, a ne isključivo natjecateljskih sportaša. Iako je do sada objavljen veliki broj knjiga i priručnika koji prikazuju razne vježbe s otporom za različite mišiće i mišićne skupine, nedostaje priručnik u kojem se detaljno opisuje metodski postupak uz prikaz niza slika karakterističnih struktura gibanja, položaja tijela, namještanja utega i trenažera prilikom izvedbe pravilne tehnike neke vježbe. Stoga je namjera autora ovog priručnika bila prikupiti i prikazati što veći broj različitih vježbi za razvoj mišićne izdržljivosti, jakosti i snage, njihovu pravilnu izvedbu po fazama, moguće varijante i tipične greške te ih kategorizirati s obzirom na mišićnu skupinu i vrstu otpora s kojom se izvode. Priručnik je stoga primjeren početnicima za samostalno učenje sadržaja, iako je prvenstveno namijenjen edukaciji stručnjaka iz područja fitnesa, ali i drugim stručnjacima u području kineziologije, trenerima i sportašima. Prvi dio priručnika opisuje osnove treninga s otporom i njegove dobrobiti te prikazuje hipotetski model razvoja mišićne izdržljivosti, jakosti i snage, dok se drugi dio odnosi na prikaz vježbi s vlastitom tjelesnom masom, slobodnim utezima, bučicama i na trenažerima

Eksploatacija geotermalne energije

S obzirom na sve veću cijenu fosilnih goriva, a i zagađenje okoliša njihovom upotrebom, sve se intenzivnije koriste obnovljivi izvori energije kao što su Sunčeva energija, energija vode, vjetra, biomase te geotermalna energija. U ovom će radu biti obrađena geotermalna energija i njezina upotreba u svrhu proizvodnje električne energije i grijanja kućanstva. Prvi dio rada opisuje samo nastajanje geotermalne energije kao obnovljivog izvora, područja s najvećim geotermalnim potencijalom, temperaturni gradijent i upotreba geotermalne energije u različite svrhe. U drugom dijelu rada obrađene su vrste geotermalnih elektrana, dijelovi od kojih se sastoje i njihov princip rada. Također su obrađene toplinske pumpe, njezini dijelovi, prednosti i mane određenih pumpi te je na jednom primjeru prikazana godišnja ušteda obiteljske kuće u odnosu na grijanje na plin. Na završetku rada napravljen je kratak osvrt na geotermalnu tehnološku inovaciju i razvoj ulaganja u geotermalnu elektranu

Osnove trreninga s otporom

Treningu s otporom u posljednjih dvadesetak godina znatno raste popularnost. To je oblik tjelesne aktivnosti koji se tradicionalno percipirao kao sastavni dio programa treninga ograničenih na vrhunske sportaše, bodybuildere i dizače utega koji nastoje poboljšati svoje izvedbe. Međutim, ta koncepcija više nije istinita. Opsežna istraživanja otkrivaju da je trening s otporom ne samo učinkovita metoda za poboljšanje mišićne izdržljivosti, jakosti i snage, nego i za poboljšanje zdravstvenog stanja većine pojedinaca, a ne isključivo natjecateljskih sportaša. Iako je do sada objavljen veliki broj knjiga i priručnika koji prikazuju razne vježbe s otporom za različite mišiće i mišićne skupine, nedostaje priručnik u kojem se detaljno opisuje metodski postupak uz prikaz niza slika karakterističnih struktura gibanja, položaja tijela, namještanja utega i trenažera prilikom izvedbe pravilne tehnike neke vježbe. Stoga je namjera autora ovog priručnika bila prikupiti i prikazati što veći broj različitih vježbi za razvoj mišićne izdržljivosti, jakosti i snage, njihovu pravilnu izvedbu po fazama, moguće varijante i tipične greške te ih kategorizirati s obzirom na mišićnu skupinu i vrstu otpora s kojom se izvode. Priručnik je stoga primjeren početnicima za samostalno učenje sadržaja, iako je prvenstveno namijenjen edukaciji stručnjaka iz područja fitnesa, ali i drugim stručnjacima u području kineziologije, trenerima i sportašima. Prvi dio priručnika opisuje osnove treninga s otporom i njegove dobrobiti te prikazuje hipotetski model razvoja mišićne izdržljivosti, jakosti i snage, dok se drugi dio odnosi na prikaz vježbi s vlastitom tjelesnom masom, slobodnim utezima, bučicama i na trenažerima

Social diversity in light of the inclusiveness of homosexually-oriented members of the Slovenian armed forces

Članek prinaša v Slovenijo prvo vojaško soci ološko raziskavo o inkluzivnosti istospolno usmerjenih pripadnic in pripadnikov v Slovensko vojsko. Na pod lagi fokusiranih strukturiranih intervjujev smo pro blematiko proučili z obeh zornih kotovs socialnega (percepcije lezbijk in gejev) in institucionalnega vidika (percepcije Slovenske vojske). Raziskava je pokazala, da so v pretežno heteronormativnem okolju istospolno usmerjene pripadnice in pripadniki Slovenske vojske – kljub varstvu dostojanstva in integritete – izpostavljeni različnim oblikam verbalne diskriminacije, nezaupa nje v disciplinske organe institucije pa jim vzbuja strah pred razkritjem istospolne usmerjenosti. Potreba po razpravljanju o tej dokaj tabuizirani problematiki je očitna, kot je nujno prepoznavanje prednosti socialne diverzitete v sodobnih vojaških organizacijahThe article brings to Slovenia the first military sociological research on the inclusion of homosexual members in the Slovenian Armed Forces (SAF). Based on focused structured interviews, we studied the issue from two standpoints: the social (perception of lesbians and gays) and institutional aspect (perception of the SAF). The research showed that in a largely heteronormative environment, homosexual members of the SAF are exposed to various forms of verbal discrimination, despite the formal protection of their dignity and integrity. The need to discuss this quite taboo issue is obvious, as is the need to acknowledge the benefits of social diversity in modern military organisation

Bilateral sequential motor cortex stimulation and skilled task performance with non-dominant hand

Objective: To check whether bilateral sequential stimulation (BSS) of M1 with theta burst stimulation (TBS), using facilitatory protocol over non-dominant M1 followed by inhibitory one over dominant M1, can improve skilled task performance with non-dominant hand more than either of the unilateral stimulations do. Both, direct motor cortex (M1) facilitatory non-invasive brain stimulation (NIBS) and contralateral M1 inhibitory NIBS were shown to improve motor learning. Methods: Forty right-handed healthy subjects were divided into 4 matched groups which received either ipsilateral facilitatory (intermittent TBS [iTBS] over non-dominant M1), contralateral inhibitory (continuous TBS [cTBS] over dominant M1), bilateral sequential (contralateral cTBS followed by ipsilateral iTBS), or placebo stimulation. Performance was evaluated by Purdue peg-board test (PPT), before (T0), immediately after (T1), and 30 min after (T2) an intervention. Results: In all groups and for both hands, the PPT scores increased at T1 and T2 in comparison to T0, showing clear learning effect. However, for the target non-dominant hand only, immediately after BSS (at T1) the PPT scores improved significantly more than after either of unilateral interventions or placebo. Conclusion: M1 BSS TBS is an effective intervention for improving motor performance. Significance: M1 BSS TBS seems as a promising tool for motor learning improvement with potential uses in neurorehabilitation

Transcranial magnetic stimulation has no placebo effect on motor learning

Objective: Motor learning is the core cognitive function in neurorehabilitation and in various other skill-training activities (e. g. sport, music). Therefore, there is an increasing interest in the use of transcranial magnetic stimulation (TMS) methods for its enhancement. However, although usually assumed, a potential placebo effect of TMS methods on motor learning has never been systematically investigated. Methods: Improvement of performance on the Purdue Pegboard Task over three test-blocks (T0, T1, and T2), separated by gt 20 min, was used to evaluate motor learning. In Experiment-1, two groups of 10 participants each were compared: one group immediately before T1 received a sham intermittent theta burst stimulation procedure (P-iTBS group), while another did not have any intervention at all (control - CON group). In Experiment-2, a third group of participants (six subjects) who received sham high-frequency repetitive TMS procedure before T1 (P-rTMS group) was compared with P-iTBS group. Results: All three groups showed significant learning over time, but without any difference between them, either in Experiment-1 between P-iTBS and CON, or in Experiment-2 between P-rTMS and P-iTBS. Conclusion: The results suggest lack of any placebo effect of TMS on motor learning. Significance: The results may help in designing further TMS-motor learning studies and in interpreting their results

Variations in polyamine conjugates in maize (Zea mays L.) seeds contaminated with aflatoxin B1: a dose–response relationship

BACKGROUND: Cereal seeds, such as maize seeds, are frequently contaminated with aflatoxin B1 (AFB1), one of the most dangerous naturally occurring carcinogens. In plants, phenolamides are involved in biotic stress response. The data on variations of phenolamides in AFB1-containing seeds are limited. RESULTS: Five polyamine conjugates, including two spermidine and three putrescine conjugates, were tentatively identified in methanolic extracts, using HPLC-DAD-MS. The ratio of putrescine to spermidine conjugates changed with increasing AFB1 concentration in a logistic dose–response manner, with a ratio of below 1 up to a concentration of 51.51 μg kg−1, and approximately 2.54 and 3 at higher concentrations of 177.4 and 308.13 μg kg−1, respectively. The observed variations of the total antioxidant activity and the total phenolic content may support this biphasic behaviour of the seeds against AFB1 stress. CONCLUSIONS: The obtained data are a contribution to the understanding of the roles of polyamine conjugates in seed defence to increasing AFB1 concentrations. According to our knowledge, this study reports for the first time the biphasic response of maize seeds to increasing AFB1 contamination level, comprising the induction of polyamine conjugate accumulation and variation in the ratio of conjugates. This dose–response relationship may provide useful information in the field of agricultural and food chemistry as an indicator of AFB1 contamination level and, hence, for selecting an appropriate seed quality

Sport-Specific Warm-Up Attenuates Static Stretching-Induced Negative Effects on Vertical Jump But Not Neuromuscular Excitability in Basketball Players

The purpose of this study was to examine the acute effects of static stretching (SS) and dynamic stretching (DS), alone and in combination with specific basketball warm-up (SBWU), on the neuromuscular excitability and vertical jump height in basketball players. Twelve healthy young male basketball players participated in the study (18 +/- 0.42 years; 17.4 - 18.6 age range; 188 +/- 9 cm; 76.5 +/- 9 kg). All participants completed two different stretching treatments (static and dynamic), performed on different days at least seven days apart, in the same period of training microcycle, in a counterbalanced order. Each session consisted of a self-paced jogging warm-up, followed by a 10-minute testing period (T0), which involved eliciting H reflex and M waves, followed by three trials of a vertical jump test. Participants then performed one of the treatment protocols. After another test (T1), participants conducted 8-minute specific basketball warm-up and then one more test (T2). Combined 3 (time) x 2 (stretching protocol) analysis of variance with repeated measures on both factors revealed that SS significantly decreased spinal excitability (H/M ratio) (p = 0.015, d = -0.38, percentage of change = -20.55%) and vertical jump height (p = 0.007, d = -1.91, percentage of change = -2.6%), but after SBWU, vertical jump height increased (p = 0.006, d = 1.13, percentage of change = 3.01%), while H/M ratio continued decreasing (p = 0.019, d = -0.45, percentage of change = -30.23%). Acute effects of DS, alone and in combination with SBWU were not significant. It seems that SBWU attenuates negative acute effects of SS on vertical jump performance in young basketball players, while DS appears to cause no significant acute effect for this population

6th International Scientific Conference on Kinesiology: Integrative power of kinesiology : proceedings book

The Faculty of Kinesiology University of Zagreb is organising the International Conference on Kinesiology for the sixth time. Everything began more than 15 years ago when the initiators – Prof. Milanović, still bursting with new ideas, and the late Prof. Mraković, started to advocate the idea of an international conference as a forum for kinesiologists or sport scientists, as a place where their research findings could be presented and discussed, as a meeting point of globally recognized scientists, or authorities in their field of research and research novices. In those days, in 1997, before the First Conference in Dubrovnik, it all seemed so surreal. However, this conference is alive; it grows and becomes ever more sophisticated. Therefore, it is feasible to expect that the forthcoming discussions, talks, dialogues, or whatever kind of idea exchange will result, as they have until now, with new research ideas, insights, research teams and projects the eventual outcome of which is further advances in kinesiology and the cognate and adjacent scientific areas. The motto of this year’s conference is the “Integrative Power of Kinesiology“. It indicates the close relationships among various scientific fields when they contribute to the promotion of physical exercise and various kinds of physical activities in the areas of kinesiological education, high performance sports, kinesiological recreation, health-enhanced kinesiology, kinesitherapy and rehabilitation, sport for physically and mentally challenged persons, school sports, military kinesiology, and many others. Simultaneously with the organisation of the 6th Conference, the Faculty of Kinesiology is celebrating the 40th anniversary of the publication of the scientific journal KINESIOLOGY. Nowadays it is a recognized international scientific journal with an IF of 0.525 for the year 2010. The Conference and the journal KINESIOLOGY have contributed considerably to the affirmation of the name “kinesiology” in the neighbouring European areas. Although both are focused on science, the Conference and the accompanying regular KINESIOLOGY International Editorial Board meetings have also been opportunities for scholars and institution delegates from all over the world to establish close personal contacts, thus opening doors for joint research projects. The basic scientific concept of the Conference, with the working sections that cover the fundamental and applicative disciplines of kinesiology, has been kept from the beginning. This year’s conference will have 12 oral and poster sections in the framework of which the delegates will present 220 full text contributions and abstracts written by 300 authors from 32 countries. Each presented and published paper or abstract has been subjected to a review process performed by at least two prominent referees. For the first time the Conference is hosting a satellite symposium HEPA (Health Enhanced Physical Activity). The purpose of the symposium is to inform delegates from the neighbouring countries, which have not yet become HEPA association member countries, with the basic principles and directives of the movement and to encourage them to become promoters of the idea of health-oriented physical activity in their communities. The World Health Organization has stimulated the design of the Croatian National Action Plan for the implementation and improvement of HEPA in the Republic of Croatia. A presentation of the Action Plan and the planned round table should also be stimulating to colleagues to undertake similar steps in their communities. From the very beginning the Croatian Academy of Sciences and Fine Arts has given its highly respected patronage to the Conference, thus underpinning the recognition of kinesiology in the structure of sciences. The organisation of such conferences would not be viable without the powerful support from the Croatian Ministry of Science, Education and Sport and the University of Zagreb. The patronage and support are indicators of a notable position the Conference and its organiser, the Faculty of Kinesiology University of Zagreb (established in 1959), have in the Croatian academic and research community. We wish to express much gratitude to all the authors of the papers, reviewers, conference participants, members of the Organisation Committee, Section Leaders, Section Secretaries, technical support staff, and sponsors for their contributions, time and effort inbuilt in the quality of the 6th Conference on Kinesiology and its Proceedings. Our special gratitude goes to the Croatian Office of the World Health Organization. We wish success in the conference work to all the participants and enjoyable time in Opatija. We are convinced the Conference will give the expected impetus to further cooperation between scholars and institutions. Looking forward in advance to meeting you again at the 7th International Conference on Kinesiology in 2014