Vježbanje na vibracijskim platformama
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Vježbanje na vibracijskim platformama

Osnovna ideja treninga na vibracijskoj platformi jest korištenje refleksne mišićne kontrakcije, putem koje se aktivira više mišićnih vlakana u jedinici vremena u odnosu na klasično vježbanje. Stoga je vrijeme potrebno za trening na vibracijskoj platformi kratko. Iz tog razloga vibracijski trening još se naziva AKCELETORNI ili ubrzan.

S obzirom na sve popularniju primjenu vibracijskog treninga, postoji više proizvođača vibracijskih platformi. Bez obzira kako intenzivno bila reklamirana, svaka vibracijska platforma ne mora pružiti rezultate opisane u mnogim studijama. Vibracijske platforme razlikuju se u svojim performansama, te iako svaku vibraciju iskusni trener može upotrijebiti u treningu, samo snažna vibracija može prouzročiti fiziološke efekte koje očekujemo od treninga.

Osnovne tri postavke koje je potrebno znati: svaka vibracija nije korisna za trening, blaga vibracija služi u terapeutske svrhe te je samo snažna vibracija korisna za trening.

Vibracijski trening

Prvi je puta tehnologija vibracijskog vježbanja upotrijebljena na ruskim astronautima, koji su u Svemiru, dakle bez blagotvornog utjecaja gravitacije na Zemlji, provodili trostruko dulje razdoblje od njihovih američkih kolega bez posljedica po zdravlje. Boravkom u bestežinskom stanju kroz dulje vrijeme, u slučaju astronauta u Svemiru, znatno se smanjuje funkcija i propada struktura koštanog (dekalcifikacija) i mišićnog sustava (hipotrofija).

Vibracijski trening potekao iz svemirskih istraživanja uspješno su rusi primijenili još jednom prije zapadnih zemalja i to u sportu 1980. godine sa dokazanim poboljšanjem performansi svojih sportaša na Olimpijskim igrama u Moskvi.

Medicinska istraživanja koja su brojna i od 80-ih do danas ih ima u svim krajevima svijeta ukazuju na blagotvoran učinak kontroliranog vibracijskog treninga na kvalitetnim spravama. Ova se vrsta vježbanja provodi znatno kraće, za slične ili bolje efekte od klasičnih načina vježbanja.

10 minuta dnevno je dovoljno za adaptacijske efekte poput:

  • poboljšanja mišićne performanse i izdržljivosti znatno brže u odnosu na druge vrste treninga (povećanje tonusa, mišićne snage, repetitivne snage i mase)
  • ubrzanja proprioceptivnog odgovora (refleksa), ubrzanje cijeljenja perifernih oštećenja
  • povećanja lučenja zglobne tekućine i njene resorpcije, stimulacije hondrocita, relaksacije na razini vezivnog omotača zgloba (zglobne čahure), sa poboljšanom fleksibilnošću
  • znatno poboljšanje strukture (kalcifikacije) kostiju već nakon kraćeg vremena
  • stimulaciju izlučivanja hormona rasta (HGH) i testosterona, dok se u isto vrijeme smanjuje produkcija kortizola
  • stimulaciju limfne cirkulacije kroz povećani mišićni tonus
  • blagi do umjereni diuretički efekt, te stimulaciju mišića mjehura i dna male zdjelice
  • stimulaciju peristaltike crijeva
  • proširenja mreže kapilara, naročito u područjima tijela u direktnom kontaktu sa vibracijskom podlogom

Mnoge od adaptacijskih i fizioloških promjena moguće je koristiti u liječenju i profilaksi bolnih i degenerativnih stanja na lokomotornom sustavu, probavnom traktu, kao i kod centralnih i perifernih neuroloških oštećenja.

Osnovni preduvjet svih opisanih fizioloških odgovora jest zadržavanje statičke pozicije tijela na vibracijskoj platformi, te serija kratkih, brzih, refleksnih mišićnih kontrakcija koju uzrokuje vibracija same podloge.

Neke od opisanih fizioloških odgovora organizma prouzročiti će bilo koja vibracija. No za anaboličku reakciju na razini kostiju i mišića, nužno je postići terapijsku dozu i to kroz vertikalnu vibraciju velike snage.

Vibracijski trening relativno je nov pristup fizičkoj aktivnosti. Iz tog razloga, ali i zbog šireg nerazumijevanja temeljne fiziologije vibracijskog podražaja, njegovih pozitivnih aspekata i opasnosti, ali i poradi potpune konfuzije o tome kakva i koliko snažna vibracija može poslužiti u svrhu treninga, u praksi se koristi široka lepeza pristupa ovom obliku vježbanja.

U daljnjem tekstu objasnit ćemo vam tipove vibracija i koja od njih ima najbolje učinke na trening, te na koje detalje je potrebno pripaziti prije nego što krenete sa vibracijski treningom.

Tri tipa vibracije

Vertikalna vibracija

Vertikalna vibracija

Znači da podloga isključivo vibrira u smjeru gore – dolje.

Takav podražaj direktno utječe na mišiće iz jednostavne činjenice u kojoj je tijelo sazdano tako da se lako može protiviti gravitacijskom povlačenju prema dolje, te su u tom smislu mišići najjači.

Povećanjem gravitacijskog povlačenja dolazi do fiziološkog odgovora organizma, prvenstveno mišićne snage, mase i izdržljivosti. U ovom slučaju gravitacijsko povlačenje povećava se vibracijom, dok se u klasičnim vježbanjem povećava utezima. Ta pravocrtna vibracija omogućuje izračun opterećenja sa samo jednom nepoznanicom, te takva jednadžba uvijek za rezultat ima cijeli broj.

Vertikalna vibracija omogućuje dizajniranje programa sa najmanjim rizikom ozljeđivanja, jer radi poznatog smjera sile moguće je postaviti tijelo u poziciju u kojoj najveći dio opterećenja preuzimaju upravo mišići koji su građeni za takav zadatak, a dok su u isto vrijeme ligamenti, hrskavica i tetive pošteđeni stresa s kojim se teško mogu nositi.

Oscilacijska vibracija

Oscilacijska vibracija

U osnovi je postranična naizmjenična vibracija, u kojoj pokret koji se događa jest najsličniji klackalici.

Kod stajanja na takvoj podlozi također se aktiviraju mišići odgovorni za stabilizaciju trupa i nogu, te je biomehanika takve kretnje drugačija od linearne vibracije. Ove podloge izuzetnu ulogu imaju u rehabilitaciji, posebno kada se brzina oscilacije može postupno povećavati.

Problem sa ovom vibracijom nastaje kod vježbi za trup ili za gornje ekstremitete, koji nisu sazdani za kvalitetnu apsorpciju naizmjenične brze kretnje kakva se događa pri primjeni ove tehnologije. Iako postoje programi i za treniranje na ovakvim podlogama, smjer, distribucija i snaga vibracije potrebne za kvalitetan mišićni anabolički odgovor može biti više no što prosječna neutrenirana osoba može svladati bez neugodnih posljedica.

Iako oscilacijska vibracija može poslužiti kao odličan podražaj za ubrzanje proprioceptivnog odgovora, pa potom i prevenciju ozljeda i cijeli niz drugih zadataka u fizioterapiji i rehabilitaciji, novije studije pokazuju da je njen utjecaj na povećanje mišićne mase, snage i izdržljivosti slab u odnosu na vertikalnu vibraciju.

3D vibracija - nekontrolirana vibracija

Ako je linearna vibracija jednadžba s jednom nepoznanicom, tada je 3D (trodimenzionalna) vibracija jednadžba s tri nepoznanice. Drugim riječima, bez obzira kako i koliko razmišljali, ne možete predvidjeti koja tkiva će primiti najviše energije iz takve vibracije. Drugi problem je u samoj konstrukciji ljudskog tijela, koji je najlakše objasniti primjerom čučnja na vibracijskoj podlozi pri kojoj se najjače aktiviraju mišići natkoljenice.

Pri vertikalnoj vibraciji koljeno je u stabilnoj poziciji i sile kroz njega djeluju u smjeru prema gore, odnosno dolje, za što je koljeno i “dizajnirano”. U koliko značajan dio vibracija ide u smjeru naprijed-natrag ili postranično, mišići, čak niti refleksno, ne mogu stabilizirati zglob, pa tako dolazi do proklizavanja glavice i čašice zgloba u svim smjerovima.

Male doze takvih vibracija možda i neće učiniti štetu, ali konstantno i uporno vježbanje s vremenom može. A koljeno je samo jedan zglob. Sličan scenarij ponavlja se i u ostalim zglobovima i pri ostalim pozicijama. Dobro je što su svi danas dostupni strojevi koji proizvode takvu vibraciju u stvari vibracijske podloge male ili srednje snage, pa je potom i rizik ozljeđivanja na njima relativno mali, a ista je i mogućnost ozbiljnijeg treninga.

Sada kada ste upoznali tipove vibracija, prije nego što počnete sa vibracijskim treningom potrebno je upoznati se i sa ostalim performansama stroja kojeg ste odabrali za trening.

Nakon što ste se raspitali koju vibraciju proizvodi, vrlo je važno obratiti pozornost na sinhroniziranost elektromotora. Većinu profesionalnih strojeva za vibracijski trening pokreću dva međusobno sinhronizirana elektromotora. Prilikom asinhronog rada motora, najbolje što se može dogoditi je gubitak snage vibracije radi negativne interferencije.

U koliko se dogodi i promjena frekvencije (koju ljudska osjetila ne mogu tako lako registrirati), tada nije moguće znati koji ćete fiziološki podražaj učiniti na tijelo. Na žalost, jedan dio plastičnih, naročito kućnih i jeftinijih „profesionalnih“ strojeva nije dobro sinhroniziran, te je konzistentnost njihove vibracije upitna.

Dalje na što trebate obratiti pozornost su materijali. Plastika je jeftinija od čelika, te je plastični stroj jeftiniji od metalnog. Istina je da plastika prigušuje vibraciju, tako da ono što proizvode motori i ono što dospijeva do vježbača zna biti vrlo različito. Problem, pak, sa čeličnim konstrukcijama jest u tome što su one teške. Dodate li tu i težinu vježbača, razumjeti ćete koju silu mora proizvesti elektromotor kako bi isporučio željenu vibraciju po frekvenciji, amplitudi i akceleraciji.

Nadalje, konzistentnost. Hoće li stroj vibrirati isto i pod težinom djevojke od 50kg i pod težinom pretile osobe od 150kg? Neki od strojeva na tržištu nisu nikada testirani pod opterećenjem, pa njihove performanse znaju drastično opasti čim stanete na njih. Posljedično, vibracija koja se prenosi na tijelo u najboljem slučaju biva slaba i bez nekog intenzivnijeg fiziološkog učinka. Upravo su ovakvi strojevi razlog razočaranja jednog dijela vježbača sa cijelim konceptom vibracijskog treninga.

Kako procijeniti „snagu“ stroja?

Nakon svega rečenog, jasno je tek jedno - performanse stroja izražene u frekvenciji i amplitudi nisu dovoljne, a drugi parametri još nisu usuglašeni. Tako ostaje samo osobno iskustvo u ocjeni koji su to strojevi koji proizvode slabu, a koji snažnu vibraciju. Isprobajte svaku tehnologiju koja vam je dostupna.

Mjerila su jednostavna

Uvjerite se da stroj proizvodi isključivo vertikalnu (linearnu) vibraciju. Oscilacijska vibracija je dobra kao terapijsko sredstvo, ali vrlo slaba kao trenažni modalitet. 3D vibracija je nekontrolirana vibracija, te usprkos svom marketingu, postoji opravdana sumnja u sigurnost njene primjene.

Vibracijski trening

Ograničite se na jednu statičku poziciju na svakome od njih. Tako ćete moći usporediti osjećaj vibracije, te vrijeme koje je potrebno da osjetite prvi ili apsolutni mišićni umor.

Izbjegavajte dinamičke vježbe. Pokretanje tijela dok stroj vibrira dovodi vas u opasnost, a dinamičke vježbe najčešće se koriste kako bi otežale vježbanje radi slabe vibracije koju sam stroj isporučuje.

Dalje, razlike u performansama vibracijskih strojeva dozvoljavaju i različit pristup kreiranju programa treninga. Interesirajte se gdje i kako je vaš "vibracijski trener" prošao svoju edukaciju i kakva i kolika su njegova iskustva.

I za kraj, sada kada ste upoznati sa vibracijskim treningom, te sa spoznajom da ono najbolje u pravilno izvođenom vibracijskom treningu jest malo utrošenog vremena za dobre rezultate u povećanju snage, smanjenju količine masnog tkiva, te poboljšanju kondicije i ukupnog zdravstvenog stanja.

Ako ste do sada izbjegavali redovito vježbanje zbog nedostatka vremena, nažalost morat ćete smisliti novi i bolji izgovor. :)

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13 Abstract of the Ph.D. Thesis The effects of vibration on human performance and hormonal profile By Marco Cardinale Semmelweis University Doctoral School Faculty of Physical Education and Sport Sciences Doctoral Program: Empirical and theoretical issues in sport sciences Program Director: Prof. Dr. Frenkl Ròbert Supervisor: Prof. Dr. Carmelo Bosco Budapest 2002 14 INTRODUCTION Skeletal muscle is a specialised tissue, which modifies its overall function capacity in response to chronic exercise with high loads (e.g. Mc Donagh and Davies 1984). The adaptation to the training stimulus is related to the modification induced by the repetition of the daily exercise, which are specific for the movement executed (Edington and Edgerton , 1976). Strength training response has been shown to be mediated by both neurogenic and myogenic factors (e.g. Moritani and De Vries, 1979). Intensive prolonged strength training is known to induce a specific neuromuscular (e.g. Sale, 1988) and hormonal (e.g. Guezennec et al ,1986 ) adaptive responses in the human body in few months ,while the changes in the morphological structure occur later ( e.g. Sale,1988). However, the exact mechanism which regulate how the body adapts to the specific demands upon it , is still unknown. In addition , even less knowledge are available in respect to fatigue, relative strength loss and hormonal changes during one acute session exercises ( e.g. Hakkinen and Pakarinen 1995). It should be remind, that strength and explosive power training specific programs are based on exercises performed with rapid and violent variation of the gravitational acceleration (Bosco, 1992). Gravity normally provides the major portion of the mechanical stimulus responsible for the development of the muscle structure during everyday life and during training. In this connection, simulation of hypergravity (wearing vests with extra loads) conditions has been utilised for enhancement of human explosive muscle power (Bosco et al., 1984; Bosco 1985). On the other hand, changes of the gravitational conditions can be produced also by mechanical vibrations applied to the whole body. In light of the above observations, it can be assumed that application of whole body vibration and/or locally applied vibrations to physical active subjects could influence the mechanical behaviour of lower and upper limbs’ muscles. Vibrations have been extensively studied in occupational medicine and ergonomics. It means that they represent some sort of stimulus to which all of us undergo in daily activities. Literature on vibration is mostly related to the study of vibrations as a diagnostic tool and on their effect on chronical exposure. In fact, most of the work has been carried out in occupational medicine and ergonomics and in animal experiments to be able to understand what is the effect of vibrations on human body. However, even if there is a respectable amount of scientific work on the topic, it is difficult to come to a consensus since different devices have been used and different vibration treatments have been utilised (changing frequency, acceleration and displacement). Moreover, the application of vibrations as an exercise tool is a rather new topic in literature (i.e. Issurin 1994, Issurin et al., 1999). Based upon the literature findings it is possible to affirm that vibrations provide a strong stimulus for the neuromuscular system, the bone and the muscle tissue itself. Not only that, hormonal responses 15 have been identified in human and animal experiments following vibrations treatments (i.e. McCall et al., 2000; Dmitriev & Tropnikova, 1988). The aim of this work was to study the effects of vibrations on human performance and hormonal profile and to provide further information for applying vibration exercise in the athletic setting. Research Hypotheses The problem addressed in this series of studies was the effect of vibrations on human performance and hormonal profile. Based upon the literature findings, the following research hypotheses were generated: 1) Prolonged administration of vibration treatments produce enhancement of neuromuscular performance similar to the improvements obtained following explosive jumping training and resistance exercise 2) Acute effects of vibrations treatment modifications of neuromuscular performance and hormonal profile similar to the ones observed following resistance exercise or explosive jumping training 3) Vibration treatment lead to an improvement of neuromuscular efficiency. METHODS A total of sixtytwo subjects voluntarily participated to the studies. They were all physically active and involved in regular exercise. Their characteristics are presented in the following table: Study Number Gender Age (years) + SD Height (cm) + SD Weight (kg) + SD 1 14 ♂ 20.2 + 0.9 179.5 + 10.1 72.8 + 5.9 2 6 ♀ 19.5 + 2.1 174.9 + 3.2 65.1 + 3.7 3 12 ♂ 20.1 + 3.1 173.7 + 7.2 69.6 + 21.4 4 14 ♂ 25.1 + 4.6 177.4 + 12.3 80.9 + 12.9 5 8 ♂ 30.7 + 5.3 188 + 4.7 89.3 + 7.2 6 8 ♂ 21.8 + 2.2 180.1 + 6.4 81.4 + 21.5 Anthropometric measures (height and weight) were recorded together with the age of the subjects at the beginning of each study. 16 Vertical Jumping. The followings jumping tests were performed: counter movement jump (CMJ) and 5s of continuous jumping (5s CJ).The flight time (tf) and contact time (tc) of each single jump were recorded on a resistive (capacitative) platform (Bosco et al., 1983) connected to a digital timer (accuracy ± 0.001s) (Ergojump, Psion XP, MA.GI.CA.Rome, Italy). To avoid un-measurable work, horizontal and lateral displacements were minimised, and the hands were kept on the hips through the test. During CMJ the knee angular displacement was standardised that the subjects were required to bend their knee approximately 90°. The rise of the centre of gravity above the ground (h in meters) were measured from flight time (tf in seconds) applying ballistic laws: h = tf2 • g • 8-1 ( m ) [1] where g is the acceleration of gravity (9.81 m•s-2). During CJ exercises the subject were required to perform the maximal jumping effort minimising knee angular displacement during contact. From the recordings of tf and tc the average mechanical power (AP), average rise of center of gravity (AH) were calculated for the total 5s continuos jumping. From 5s CJ the best jumping performance was selected and maximal mechanical power (PBJ) as well as the highest rise of center of gravity (HBJ) were obtained using the equation introduced by Bosco et al. (1983) : AP = Tf • T • 24.06 • ( Tc )-1 (W • kg bm-1) [2] where P is the mechanical power per kilogram of body mass, Tf the sum of the total flight time, Tt the total working time (5s), and Tc the sum of the total contact time. The average height during 5s CJ and the HBJ were computed using formula [1]. The reproducibility of the mechanical power test (5s CJ) and CMJ performances were high with respectively r=.95 and r =.90 (Bosco et al., 1983; Viitasalo & Bosco, 1982). Iso-inertial dynamometry was implemented in study 2,3,4,5 and 6. During the test, the vertical displacements of the loads were monitored with simple mechanics and sensor arrangement (Muscle Lab®, Ergotest Technology A.S., Langensund, Norway). The loads were mechanically linked to an encoder interfaced to an electronic microprocessor (Muscle Lab, Pat. No.1241671). When the loads were moved by the subjects a signal was transmitted by the sensor every 3mm of displacement. Thus it was possible to calculate average velocity (AV), acceleration, average force (AF), and average power (AP), corresponding to the load displacements (for details see Bosco et al., 1995). The dynamic exercises reproducibility testing gave a test-retest correlation r = 0.95 for the average power (P) (Bosco et al., 1995). Electromyography. EMG analyses were performed with bipolar surface electrodes (interelectrode distance 1.2 cm) including an amplifier (gain 600, input impedance 2Giga , CMMR 100dB, bandpass filter 6-1500 Hz; Biochip Grenoble, France) fixed longitudinally over the muscle belly. The MuscleLab converted the amplified EMG raw signal to an average root-mean-square (rms) signal 17 via its built in hardware circuit network (Frequency response 450kHz, averaging constant 100ms, total error ± 0.5%). The EMGrms was expressed in function of the time (millivolts or microvolts). Since the EMGrms signals were used in relation with bio-mechanical parameters measured with MucleLab, they were simultaneously sampled at 100Hz. The subjects wore a skin suit to prevent the cables from swinging and from causing movement artefact. A personal computer (PC 486 DX- 33MHz) was used to collect and store the data. Hormonal measurement. The first blood samples were drawn at 08:00 a.m from an antecubital vein after 12 hours fasting and 1 days resting. The second blood sample was obtained right after the end of the vibration treatment. The subjects were asked to sit near to the vibration machine, where an appropriate setup was prepared for blood collection. The blood samples were drawn in the 1-min following the end of the vibration treatment. Serum samples to be used for hormone determinations were kept frozen at –20°C until assayed. The assay for serum total T and cortisol ( C) were performed by radioimmunoassay (RIA) using reagent kits (Diagnostic Products Corporation, Los Angeles California, USA). Growth hormone was measured using RIA reagent kits obtained from radium (Pomezia, Italy). All samples from the tested subjects were analysed using RIA counter (COBRA 5005, Packard Instruments, Meriden, USA). The intra-assay coefficients of variations for duplicate samples were 3.63% for T, 5.1% for C and 2.1% for GH. Blood lactate measurement. Peak lactate concentration was determined from the subject’s ear lobe blood samples before test-1, and 3-5-7 min after 30r-N and 30r-V. The tests were de-proitenezed in ice -cold percloric acid for subsequent analysis of lactic acid (Enzymatic method, Biochimica, Boehring, Mannheim, Germany). Statistical methods. Ordinary statistical methods were employed, including the calculations of means and standard deviation. The Pearson product moment correlation coefficient (r ) was used for test re-test measurement reliability and for correlational analyses. The SD and CV of test re-test measurement were calculated using the following equation (Thorstensson 1976) 1 1 2 ) ( ) 2 CV = (200x SD x x + x − [3] where x1 and x2 are the mean average values of two successive measurements , and SD is the standard deviation of the mean differences between test re-test measurements. Differences between the mean values before and after the vibration treatment were tested for significance using Student’s t-test for paired observations. Repeated measures ANOVA was also used in study 6. For all the studies, alpha was set at p
vibe
11.02.12. u 15:51
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Postoje dokazi kako su skupine vježbača poboljšale snagu,eksplozivnost,kosti itd u odnosu na drugu skupinu koja je radila iste stvari ali bez platforme.. islim da je vrijeme da završimo temu :-) i nadjemo se na nekoj drugoj :-)
vibe
11.02.12. u 15:53
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Strength Increase after Whole-Body Vibration Compared with Resistance Training CHRISTOPHE DELECLUSE1, MACHTELD ROELANTS1, and SABINE VERSCHUEREN2 1Exercise Physiology and Biomechanics Laboratory, and 2Laboratory of Motor Control, Faculty of Physical Education and Physiotherapy, Department of Kinesiology, Katholieke Universiteit Leuven, Leuven, BELGIUM ABSTRACT DELECLUSE, C., M. ROELANTS, and S. VERSCHUEREN. Strength Increase after Whole-Body Vibration Compared with Resistance Training. Med. Sci. Sports Exerc., Vol. 35, No. 6, pp. 1033–1041, 2003. Purpose: The aim of this study was to investigate and to compare the effect of a 12-wk period of whole-body vibration training and resistance training on human knee-extensor strength. Methods: Sixty-seven untrained females (21.4  1.8 yr) participated in the study. The whole-body vibration group (WBV, N  18) and the placebo group (PL, N  19) performed static and dynamic knee-extensor exercises on a vibration platform. The acceleration of the vibration platform was between 2.28 g and 5.09 g, whereas only 0.4 g for the PL condition. Vibration (35–40 Hz) resulted in increased EMG activity, but the EMG signal remained unchanged in the PL condition. The resistance-training group (RES, N  18) trained knee extensors by dynamic leg-press and leg-extension exercises (10–20 RM). All training groups exercised 3 wk1. The control group (CO, N  12) did not participate in any training. Pre- and postisometric, dynamic, and ballistic knee-extensor strength were measured by means of a motor-driven dynamometer. Explosive strength was determined by means of a counter-movement jump. Results: Isometric and dynamic knee-extensor strength increased significantly (P  0.001) in both the WBV group (16.6  10.8%; 9.0  3.2%) and the RES group (14.4  5.3%; 7.0  6.2%), respectively, whereas the PL and CO group showed no significant (P  0.05) increase. Counter-movement jump height enhanced significantly (P  0.001) in the WBV group (7.6  4.3%) only. There was no effect of any of the interventions on maximal speed of movement, as measured by means of ballistic tests. Conclusions: WBV, and the reflexive muscle contraction it provokes, has the potential to induce strength gain in knee extensors of previously untrained females to the same extent as resistance training at moderate intensity. It was clearly shown that strength increases after WBV training are not attributable to a placebo effect. Key Words: MUSCLE STRENGTH, TONIC VIBRATION REFLEX, COUNTER-MOVEMENT JUMP, STRENGTH TRAINING Whole-body vibration (WBV) is a neuromuscular training method that has recently been developed. In WBV training, the subject stands on a platform that generates vertical sinusoidal vibration at a frequency between 35 and 40 Hz. These mechanical stimuli are transmitted to the body where they stimulate in turn sensory receptors, most likely muscle spindles. This leads to the activation of the alpha-motoneurons and initiates muscle contractions comparable to the earlier described “tonic vibration reflex” (6,11,15). Initially, WBV training was used in elite athletes to improve speed-strength performance. More recently, it is becoming tremendously popular in European health and fitness clubs as an alternative training method. However, there is still a lack of scientific support about the benefits of WBV on fitness and health. Bosco et al. (3,5) found an increase in force-velocity, force-power and vertical- jump performance immediately after one WBV session. A placebo controlled study showed that a single bout of WBV transiently improves isometric strength of the knee extensors and vertical-jump performance by 3.2% and 2.5%, respectively (22). These effects were recorded 2 min after the intervention but disappeared in the next 60 min. Some studies analyzed the effect of WBV training on muscle performance over a longer period. Bosco et al. (2) reported the effect of a 10-d training program of a daily series (5  90 s) of vertical sinusoidal vibrations at a frequency of 26 Hz. They found a significant improvement of the height and mechanical power during the 5-s continuous- jumping test. It was suggested that WBV training finally might result in neuromuscular adaptations similar to the effect produced by explosive strength training. However, 10 d of training is too short to determine the long-term effects of WBV. Runge et al. (20) showed gains of 18% in chair-rising time in elderly persons after 12 wk WBV training (27 Hz). Recently, Torvinen et al. (23) reported a significant increase in jump performance (8.5%) and a nonsignificant increase in isometric limb extension strength (2.5%) after a 4-month WBV intervention (25–30 Hz) in young nonathletic adults. As none of these long-term studies were placebo controlled, it is impossible to determine whether the training effect on strength and jump performance resulted from the exercises that were performed on the platform or Address for correspondence: Christophe Delecluse, Ph.D., Faculty of Physical Education and Physiotherapy, Tervuursevest 101, 3001 Leuven, Belgium; E-mail: christophe.delecluse@flok.kuleuven.ac.be. Submitted for publication October 2002. Accepted for publication January 2003. 0195-9131/03/3506-1033 MEDICINE & SCIENCE IN SPORTS & EXERCISE® Copyright © 2003 by the American College of Sports Medicine DOI: 10.1249/01.MSS.0000069752.96438.B0 1033 from the vibration induced muscle activation. Additionally, there are no studies available to compare the effect of WBV and resistance training on muscle strength. This is the first long-term study to differentiate between the effects resulting from the exercises performed on the platform with vibration and without vibration (placebo) and to compare the effects of WBV training and resistance training by means of weight machines at moderate intensity. Therefore, the changes in isometric, dynamic, ballistic kneeextensor strength, and counter-movement jump (CMJ) height were analyzed in young female adults after a 12-wk training period. As WBV elicits a high degree of muscle activation, it was hypothesized that WBV would result in strength increase in previously untrained persons. These strength increases should be significantly larger than the training effects resulting from an identical exercise program performed in absence of vibration (placebo condition). As the tonic vibration reflex facilitates the activation of high-threshold motor units and the reflex sensitivity (1,18), WBV training may be more efficient to improve ballistic strength and jump performance compared with resistance training at moderate intensity. METHODS Experimental Approach to the Problem A four group prepost design was used in this study to determine whether a 12-wk period of WBV-training (3 times/wk) would result in a considerable increase in kneeextensor strength, and whether WBV training, compared with moderate resistance training, would be more efficient to improve ballistic and explosive strength in previously untrained subjects. The four groups included a WBV group, a resistance-training group, a control group, and a placebo group. This latter group was added to determine whether the expected training effect in the WBV group resulted from the exercises that are performed on the platform or from the vibration induced muscle activity. Isometric strength, dynamic strength, and ballistic strength of the knee extensors were measured in pre- and post-test conditions. Explosive strength was measured by means of a CMJ. Subjects and Study Design A group of 74 young female adults (age 21.5  1.9 yr; body mass 61.6  9.1 kg; height 165.3  10.3 cm) volunteered to participate in the study. None of them were engaged in regular organized physical activities nor in sports or strength training. Reasons for exclusion were pregnancy, acute hernia, and any history of severe musculoskeletal problems. Subjects with a history of diabetes or epilepsy were also excluded from the study. All subjects were informed about the training and test protocol and about the possible risks and benefits of the study. They all gave written informed consent to participate. This study was approved by the University’s Human Ethics Committee according to the declaration of Helsinki. Power analysis revealed that a sample size of 17 subjects in the experimental groups was necessary to achieve a power of 0.80 with   0.05. In anticipation of inevitable dropout, it was decided to select a minimum of 20 subjects in the experimental groups. All subjects were randomly assigned to one of three interventions: the whole-body vibration (WBV, N  20), the placebo vibration (PL, N  21), the resistance training (RES, N  20), or a control group (CO, N  13). All intervention programs consisted of 36 training sessions within a 12-wk period. Training frequency was three times a week with at least 1 d of rest between two sessions. The control group did not participate in any training program. WBV and PL Conditions The subjects of the WBV group and the PL group performed static and dynamic knee-extensor exercises on the vibration platform: squat, deep squat, wide-stance squat, one-legged squat, and lunge. At the moment, there are no scientific-based, long-term WBV-training programs available. Therefore, we developed a 12-wk WBV program with a low training load at the beginning but slowly progressive according to the overload principle. The training volume increased systematically over the 12-wk training period by increasing the duration of one vibration session, the number of series of one exercise, or the number of different exercises. The training intensity was increased by: shortening the rest periods or by increasing the amplitude (2.5–5 mm) and/or the frequency (35–40 Hz) of the vibration (Table 1). The vibration platform (Power Plate®) produced vertical sinusoidal vibrations at a frequency between 35 and 40 Hz. The peak-to-peak amplitude of the vibration was 2.5 mm at low amplitude and 5 mm at high amplitude. The acceleration of the platform as recorded by means of an accelerometer (Monitran, MTN 1800) varied between 2.28 g and 5.09 g (Table 2). In the PL condition, the subjects, standing on the platform, could hear the motor and experienced tingles on their foot soles, but the acceleration of the platform was only 0.4 g (Table 2) with a negligible amplitude. Bipolar surface EMG (Noraxon Myosystem 2000), recorded from m. rectus femoris and from m. gastrocnemius, illustrates the difference between the impact of the WBV condition and the PL condition on muscle activity. Standing in the squat posture on the platform during WBV leads to an TABLE 1. Training volume and training intensity of the WBV program. Start End Volume Total duration of vibration in one session (min) 3 20 Series of one exercise (N) 1 3 Different knee-extensor exercises (N) 2 6 Longest duration of vibration loading without rest (s) 30 60 Intensity Rest period between exercises (s) 60 5 Vibration amplitude (mm) 2.5 5 Vibration frequency (Hz) 35 40 The status of each variable is described at the start and at the end of the 12-wk training period. 1034 Official Journal of the American College of Sports Medicine http://www.acsm-msse.org increase in muscle activity for the m. rectus femoris and the m. gastrocnemius, whereas the PL condition did not (Fig. 1). During all of the vibration-training sessions, the subjects wore the same gymnastic shoes to standardize the damping of the vibration due to the footwear. The subjects were asked to report possible side effects or adverse reactions in their training diary. Every 3 wk, exercise supervisors performed an inquiry into the attitude and the satisfaction of the subjects in both groups. As the WBV group and the PL group exercised in different rooms and at different moments, they could not compare both conditions, and they could not share their training experiences. Exercise specialists closely supervised all training sessions of all intervention groups. Resistance Training The RES group trained in the university fitness center. After a standardized warming-up consisting of 20-min stepping, running, or cycling, they performed a moderate resistance- training program for knee extensors on a leg-press and a leg-extension apparatus (Technogym®). The resistancetraining program was slowly progressive, similar to the WBV program, starting at a low threshold of 20 RM in the first 2 wk. The training load was first increased to 15 RM in the next 3 wk, followed by another 3-wk period at 12 RM. Subjects trained at 10 RM during the last 4 wk. Leg press and leg extension exercises were executed systematically to fatigue failure with the objective to perform the prescribed number of repetitions. The starting load was determined by an exercise specialist at the first training session. During the whole training period, subjects were observed, and they were instructed to increase the resistance systematically in the after set or in the following session if they were able to perform the current workload for two or more repetitions over the prescribed number (14). The subjects performed two sets of repetitions on each apparatus with at least 1 min of rest in between. Tests The contractile properties of the knee extensors were evaluated at the start (pretest) of the study and after 12 wk of training (posttest). All subjects participated in a standardized warm-up and test protocol on a motor-driven dynamometer (REV9000, Technogym®), consisting of isometric tests, dynamic tests, and ballistic tests for the knee extensors. In addition, all subjects performed a vertical CMJ. The subjects were asked to perform all these tests at maximal intensity. During a standardized warm-up, the subjects exercised the different types of contractions to experience all test conditions before testing. Posttests were performed at least 72 h after the last training session to avoid any acute effect of training sessions on test results. Dynamometry. The isometric, dynamic, and ballistic tests were performed unilateral on the right side, in a seated position on a backward inclined (15°) chair. The upper leg, the hips, and the shoulders were stabilized with safety belts. The rotational axis of the dynamometer was aligned with the transverse knee-joint axis and connected to the distal end of the tibia by means of a length-adjustable rigid lever arm. The alignment of the dynamometer was systematically controlled by inspecting the position of the lever arm with respect to anatomical reference points during passive movements. The three-dimensional positions of the rotational axis, the position of the chair, and the length of the lever arm were identical in pre- and post-test condition. Isometric strength (ISO). The subjects performed twice a maximal voluntary isometric contraction of the knee extensors. The knee joint angle was 130°. The isometric contractions lasted 3 s each and were separated by a 2-min rest interval. The highest torque (N·m) was recorded as isometric strength performance. The intraclass correlation coefficient (ICC) for test-retest reliability of isometric strength, recorded in a comparable group of untrained females, was 0.93. Dynamic strength (DYN). The subjects performed a series of four consecutive isokinetic flexion-extension movements against the lever arm of the dynamometer that moved at a velocity of 100°·s1. The knee extension was initiated at a joint angle of 90° and ended at 160°. After each extension, the leg was returned passively to the starting position from which the next contraction was immediately initiated. Maximal dynamic strength was determined as the peak torque (N·m) recorded during these series of knee extensions. The ICC for test-retest reliability of dynamic strength, recorded in a comparable group of untrained females, was 0.98. Ballistic strength (BAL). The subjects performed four ballistic tests for the knee extensors. They were asked to extend the lower leg at the highest possible speed from a knee-joint angle of 90° to an angle of 160°. This exercise was performed once without external resistance on the lever arm (0%), followed by three identical tests with a controlled resistance on the lever arm. Hereby the degree of resistance was individually determined at a percentage of the isometric maximum in the knee angle from where the movement was initiated (90°). The ballistic tests were performed with a resistance of 20%, 40%, and 60% of this isometric maximum. At each test, the maximal velocity of the lever arm (°·s1) was recorded to determine ballistic strength. The ICC for test-retest reliability of the maximal velocity during ballistic tests, recorded in a comparable group of untrained females, varied between 0.87 and 0.96, dependent on the resistance. TABLE 2. Maximal acceleration (g) on the WBV platform at low (2.5 mm) and high (5 mm) peak to peak amplitude and on the PL platform (amplitude negligible). AMP FREQ WBV Platform PL Platform Low 35 Hz 2.28 0.38 40 Hz 2.71 0.37 High 35 Hz 3.91 0.41 40 Hz 5.09 0.40 g is the Earth’s gravitational field or 9.81 ms2. AMP is the vibration amplitude. FREQ is the vibration frequency. STRENGTH INCREASE AFTER WHOLE-BODY VIBRATION Medicine & Science in Sports & Exercise 1035 Explosive strength. A vertical CMJ with hands positioned in the waist was used to assess the lower-limb explosive performance capacity (4) after stretch shortening of the muscles. This test was performed on a contact mat, recording the flight time in milliseconds. The obtained flight time (t) is further used to determine the increase in the center of gravity (h), i.e., h  gt2/8, where g  9.81 m·s2. The best of three trials was recorded to determine the test score. The ICC for test-retest reliability of CMJ performance, recorded in a comparable group of untrained females, was 0.99. FIGURE 1—Root means square (RMS) EMG activity (mV) in the m. rectus femoris (top) and in the m. gastrocnemius (bottom) recorded in static half squat position. The preamplified signal (gain 80 dB) was bandpass filtered (15–10,000 Hz) before sampling at 2000 Hz. RMS-EMG activity was calculated of the rectified EMG signal for a period of 10 s prior vibration, during vibration, and after vibration at 35 Hz with a vertical peak to peak amplitude of 5 mm. 1036 Official Journal of the American College of Sports Medicine http://www.acsm-msse.org Statistical Analysis The effect of the different interventions on strength parameters was analyzed by means of ANOVA for repeated measures [4 (group)  2 (time)] (GLM) using the least square method (LS means). After an overall F-value was found to be significant, preplanned contrast analyses were performed to evaluate the significance of effects (prepost, between groups). A Bonferroni correction was used to adjust the P-value in relation to the number of contrasts that were performed. All analyses were executed using the statistical package Statistica, version 6 (Statsoft, Inc.). Significance level was set on P  0.05. RESULTS Training experiences, compliance, and drop-out. In the WBV and PL groups, subjects acquainted very rapidly the exercise protocol. There were no reports of adverse side effects. Most subjects experienced the vibration loading (WBV group) as enjoyable and fatiguing, but they did not consider it as a hard workout. The supervising staff reported no doubts, concerning the training modalities, in the PL group. All of these subjects (PL) felt confident that they were participating in a real WBV program. During the first weeks of the study, seven subjects dropped out: two subjects of each training group (RES, WBV, and PL), respectively, and one subject of the CO group. All of these drop-outs were related to an incompatibility of the test/training program and other commitments (e.g. work, studies, etc.) of the subjects. All remaining subjects of the training groups (WBV, PL, and RES) performed 36 training sessions. Some subjects needed one extra week to complete all sessions, as they missed up to three sessions during the 12-wk period. The characteristics of the 67 subjects that completed all pre and post tests are given in Table 3. No significant differences in age, body mass, and height among all groups were detected at the start of the study (Table 3). Muscle performance. For isometric strength a significant interaction effect (group  time) was found [F(3)15.94, P  0.001]. Contrast analysis clarified that isometric knee-extensor torque (Fig. 2) increased significantly (P  0.001) over 12 wk in the RES group (14.4  5.3%) and in the WBV group (16. 6  10.8%) whereas no significant increase was found in the PL- or the CO group. Regarding dynamic strength a significant interaction effect [F(3)7.81, P  0.001] was found. Contrast analysis showed a significant increase (P  0.001) in dynamic strength (Fig. 2) for the RES group (7.0  6.2%) and the WBV group (9.0  3.2%). The PL group and the CO group did not improve in dynamic strength. The ballistic test results (Fig. 3) revealed no significant effect (P  0.05) in unloaded speed of movement (0%) or in speed of movement with standardized resistance (20%, 40%, or 60% of maximal isometric strength). CMJ height showed a significant interaction effect (group  time) [F(3) 5.88, P  0.001]. Contrast analysis clarified that jumping height increased significantly (P  0.001) over 12 wk in the WBV group (7.6  4.3%), but remained unchanged in all other groups (Fig. 4). DISCUSSION This is the first placebo-controlled study that compares the effects of 12 wk of WBV training and resistance training on knee-extensor strength and CMJ performance in previously untrained subjects. The results of this study clearly FIGURE 2—Mean and SD before (pre) and after (post) 12 wk in the RES, WBV, PL, and CO groups. Top: maximal isometric knee-extensor torque (ISO). Bottom: maximal dynamic knee-extensor torque (DYN). † refers to a significant interaction (group  time) effect at P
vibe
11.02.12. u 15:55
line
Nekako mislim da ekipa nece citati ovolike postove.

Ubuduce, bolje ostavite link nego ovakav copy/paste.
Zoki
11.02.12. u 16:32
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Nije do ovolikog posta, nego je užasno nepregledno... isto tako molim link
Iluvatar
11.02.12. u 23:21
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Da , istina,ako netko zbilja zanima da ne raspravljamo na razni ..ja mislim..rado ću poslati sve radove u pdf-u na mailove. Pozdrav
vibe
11.02.12. u 23:24
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Vibe, sve to stima, vjerujem da koristi u rehab svrhe, inicijalno poboljsanje kod netreniranih ljudi kao sto su kolko vidim studije i radjene na njima, ta oprema je i onako izmisljena u tu svrhu i za ocuvanje nekog prihvatljivog stanja u bestezinskim uvijetima ako se ne varam, ali sumnjam da utrenirani ljudi mogu puno imati koristi od ovog?
The Phoenix
12.02.12. u 09:12
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Nije samo u rehab svrhe,mogu ti poslati radove mjerene na profesionalnim sportašima i to mjereno po segmentima.. Nemoj misliti da bi u toj industriji uložili toliko novaca bez mnogo godina istraživanja i testiranja,samo što se kod nas malo zna o tome.. Nekad je to bilo preskupo i nedostupno,i sada poprilično košta ali je ipak dostupnije.. Osobno sam radio pripreme sa poznatim našim sportašima(neću navoditi imena) i dobili povećanje snage koje nikako nisu mogli postići redovnim putem. Izmejereno,provjereno istestirano,polučilo rezultate kako u mjerenjima tako i u takmičenju za koju svrhu je i rađeno. Pozdrav
vibe
12.02.12. u 12:15
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moze, slobodno posalji


The Phoenix
12.02.12. u 23:07
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Može i meni molit ću, uvjek je dobro nešto novo naučiti.
Iluvatar
19.02.12. u 14:05
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Objavljeno: 08.02.2012
Piše:
Ana Žigman, prof. kineziologije