FREE ELECTRONIC LIBRARY - Abstract, dissertation, book

Pages:     | 1 |   ...   | 156 | 157 || 159 | 160 |   ...   | 192 |

«Hosted by the: National Institute of Physical Education of Catalonia (INEFC) ISBN 978-84-695-7786-8 European College of Sport Science: Book of ...»

-- [ Page 158 ] --

Technical University of Munich, Faculty of Sport Science INTRODUCTION Although the phenomenon of residual force enhancement (RFE) is well known and has been systematically observed from single sarcomeres to in vivo human muscles, its relevance for everyday movements performed with submaximal efforts remains unclear. Therefore, the aim of this study was to investigate the idea of RFE being a more effective and energy saving muscular property during an everyday like submaximal multi-joint leg extension. METHODS Subjects (n = 13) performed bilateral isometric (100° knee flexion) and stretch contractions (80-100° knee flexion at 60°/s with subsequent isometric contractions) in a motor driven legpress dynamometer at submaximal efforts of 30% vastus lateralis (VL) EMG (EMG-control) and 30% Fmax (force-control), respectively. Further, subjects performed purely isometric and stretch contractions at 50% force-control until time to failure. External reaction forces were measured by 3D force plates and activity of 9 lower leg muscles was assessed using EMG. Kinematics were analysed by a VICON system and inverse dynamics served for calculating ankle, knee, and hip joint torques. Visual feedback of VL EMG or external reaction force was given to control submaximal efforts. RESULTS For EMG-control we found no differences in VL activity between isometric and stretch contractions but significant RFE at the level of external reaction forces and joint torques. During isometric contractions after stretch, forces and joint torque exceeded the purely isometric references up to 22% and were present for up to 22s post stretch. For force-control preliminary results showed no differences in external reaction forces between contraction types but vice versa to EMG-control, less muscular activity was required to produce the given force of 30% Fmax during the isometric contraction after stretch. After stretch, activity of knee extensor and plantar flexor muscles was reduced up to 38% and 48% compared to the purely isometric contractions. The time to failure contractions showed that after stretch a given force of 50% Fmax could be maintained longer than during an isometric contraction without preceding stretch. DISCUSSION Although former studies demonstrated the existence of RFE for submaximal contractions, this is the first study to show RFE to occur during an everyday like multi-joint leg extension performed with submaximal effort. In the light of being beneficial for everyday movements the finding of reduced activity after stretch when producing a given force might be more important than the ability of generating higher forces during EMG-control. Further high correlations between time to failure and muscular O2-cosumption suggest the mechanisms underlying RFE to be energy saving. ACKNOWLEDGEMENTS This work was funded by the German Research Foundation (SCHW1169/3-2) – www.dfg.de.



Hunter, A.M., Pahar, M., Balshaw, T.G.

University of Stirling Introduction Resistance exercise performed with overload of the eccentric phase (AEL) can lead to superior strength gains compared to constant load (CL) exercise (Hortobagyi et al., 2001). Initially, strength adaptations occur from increases in neural drive (Selvanayagam et al., 2011); therefore, it is possible that acute altered neural responses could contribute to this stimulus. Our aim was to investigate motor unit recruitment and common drive (CD) (motor unit discharge rate) following AEL in comparison to CL protocols at 2 different eccentric velocities (4 or 2 seconds). Methods Ten healthy males attended the laboratory on 4 separate occasions in random order to perform a maximal isometric voluntary contraction (MVC) followed by a 10 second submaximal trapezoid contraction (70% of MVC)(TRAP) during which high density EMG (De Luca and Hostage., 2010) recorded firing rates of motor units from the vastus lateralis (VL). CD was then analysed from the 3-second plateau phase of the TRAP with the greatest reliability. Then, the participants either did CL (2s), AEL (2s), CL (4s) or AEL (4s). AEL and CL consisted of eccentric load at 120% and 85% of 3RM respectively. All conditions consisted of a concentric load of 85% of 3RM which consisted of 3 x 3, and then MVC and TRAP was repeated. Global EMG was also recorded from the VL during these contractions and was normalised to baseline dynamic strength tests. Results For all interventions no alterations where shown in MVC

following exercise, also no differences occurred in concentric velocity between conditions. Normalised EMG amplitude (RMS) was significantly (p0.01) greater in the eccentric phase in AEL vs. CL for both fast (f) and slow (s) contractions (AEL:193.7 + 6.5% f 192.7 + 6% s CL:

145.3 + 5% f 135.4 + 5% s). No differences were observed between conditions for CD. For all conditions peak cross-correlation histogram frequency appeared in the range of 0.6 to 0.7 and no differences were shown for maximum and mean peak cross-correlation coefficients (p 0.05). Discussion Despite the additional load maximal force capacity of the knee extensors was maintained following AEL.

Although there was an increase in motor units recruited during the eccentric phase of AEL there was no alteration in common drive following the intervention. This has therefore demonstrated that AEL increases motor unit recruitment but not in residual common drive in response to a heavier load. Thus, it is likely that neuromuscular responses in the eccentric phase of AEL are responsible for superior adaptations previously reported. References De Luca CJ and Hostage EC. J Neurophysiol 2010;104(2):1034-1046. Hortobagyi T, Devita P, Money J, Barrier J. Med Sci Sports Exerc 2001;33(7):1206-1212. Selvanayagam VS, Riek S, Carroll TJ. J Appl Physiol 2011;111(2):367-375.

–  –  –


Paizis, C., Fautrelle, L., Baroudi, A.R., Deley, G., Babault, N.

University of Burgundy Introduction Numerous epidemiological studies demonstrated that lateral ankle sprain (LAS) is a recurrent problem in athletes (Hootman et al. 2007). Further to LAS, residual symptoms could arise and about 70% of the athletes who suffered from acute LAS develop chronic ankle instability (Hertel 2002). At the muscular level, evertor muscles strength is an essential factor in order to ensure ankle stability (Wilkerson et al. 1997). In this study, we proposed to investigate the modulation of the EMG activity of 6 ankle muscles (on the right and left leg) when wearing an ankle destabilisation device (ADD) in different situations. We hypothesized that ADD would significantly modify the amplitude of the EMG pattern of the ankle muscles, especially in peroneal muscles. Methods Twelve healthy active subjects without previous history of neuromuscular disease or acute LAS volunteered for the experiment. Subjects were required to walk forward and backward, on both sides and in circles, with or without the ADD. They were then asked to maintain unipodal equilibrium with a Freeman board. Kinematics and surface electrical activities were recorded on six muscles of both legs, namely the tibialis anterior, peroneus longus, peroneus brevis, gastrocnemius lateralis, gastrocnemius medialis and soleus. EMG activity recorded during each experimental condition was normalized by the EMG activities recorded during a maximal voluntary isometric contraction. Results Electromyographic recordings showed a significantly increased activity during dynamic equilibrium but also when wearing ADD during normal walk forward and backward, circle walking in both directions (P0.05). Discussion Our findings evidenced that walking in different conditions with ADD generates a significant increase in electromyographic activity of tibialis and both peroneus muscles, and therefore suggest that ADD are a valuable resource for functional strength training, sensory-motor rehabilitation and prevention of the ankle injury. References Hootman JM, Dick R, Agel R. (2007). J Athl Train, 42: 311-9. Hertel J (2002). J Athl Train, 37: 364-375 Wilkerson GB, Pinerola JJ, Caturano RW (1997) J Orthop Sports Phys Ther, 26: 78-86.



Fry, A., Folland, J.P.

Loughborough University Introduction The role of afferent feedback in maximal motor tasks remains poorly understood. Whilst it has been suggested that a reduced efficacy of the γ-loop following tendon vibration may impair maximal voluntary force, the limited previous studies have been equivocal in their findings. Furthermore, the effect of vibration, and attenuation of the γ-loop, on explosive force production is unknown.

The aim of this study was to investigate the role of afferent feedback in maximum and explosive isometric force production of the quadriceps, using a prolonged tendon vibration to attenuate the Ia afferent-α-motoneuron pathway. Methods Eighteen healthy males (21±2 years) performed a series of voluntary and evoked isometric unilateral knee-extensor contractions pre and post two separate 30-min intervention trials of: infrapatellar tendon vibration (80 Hz) and quiet sitting (control), 7 days apart. Participants performed six explosive and two maximal force contractions to assess volitional function, and supramaximal twitch and octet responses were evoked to assess the contractile properties of the muscle-tendon complex. The efficacy of the Ia afferent-α-motoneuron pathway was determined by assessing the H-reflex (Hmax:Mmax ratio of the vastus medialis) at rest, at the start and end of each series of volitional and evoked contractions, pre and post intervention (i.e. at four time points). Participants remained seated in a strength testing chair throughout the trials, with knee and hip angles of 120° and 105°, respectively. Force was measured via a strain gauge strapped perpendicular to the tibia, and surface EMG was recorded from six sites over the quadriceps and two over the hamstrings. Results Post-intervention Hmax:Mmax was 60% lower in the vibration trial vs. control, and remained 38% lower at the end of the post-intervention measurements (t-test, both P0.01). In contrast, no trial × time interactions were found for either maximum force (ANOVA, P=0.92) or explosive force (at 50, 100 and 150 ms after force onset; ANOVA, all P≥0.36), or their corresponding mean agonist EMG amplitude (ANOVA, all P≥0.23). Evoked responses were also unchanged following vibration (ANOVA, all P≥0.39). Individual Hmax:Mmax depression did not correlate to changes in either maximum or explosive force (Spearman’s Rank, all P≥0.54). Discussion The reduction in H-reflex demonstrated that the vibration stimulus effectively attenuated the homonymous Ia afferent-α-motoneuron pathway for the duration of the post-intervention measurements. However, voluntary maximal and explosive force production remained unchanged. Therefore, Ia afferent feedback does not appear to contribute significantly to either maximal or explosive isometric force production of the quadriceps.


Pencheva, N., Kokova, M., Dencheva, S.

South-West University Introduction The aims of this study are: (1) to obtain knowledge of the isometric torque-angle relationship of the elbow flexors and extensors; (2) to explore the impact of the elbow angle on the neuromuscular activity of the biceps brachii – long head (BB-LH) and triceps brachii – long head (TB-LH) by recording sEMG activity; and (3) to evaluate the correlations between the isometric flexor or extensor torque and RMS of the muscles tested. Methods Maximal isometric torque of flexors and extensors were measured (Biodex System 4) over a wide range of angles (15-150o) in ten females (21.2±1.4 years). Agonistic EMG activity and the level of coactivation for BB-LH and TB-LH were also measured. The curve fitting and statistics were performed by Prism software. Results The isometric torque-angle curves of flexors and extensors were modeled with 4th order polynomial function. The maximal torque of flexors (28.0±7.5 Nm) was generated at 90-105o position, while that of extensors (28.9±6.7 Nm) at 60-75o. The flexors/extensors torque ratio was lower, equal or higher than 100 % in the angular positions of 15-75o, 90o or 105-150o respectively. Agonistic EMG activity level of the BB-LH, as RMS, was correlated to measured torque of flexors, within the range of 75-150o (Spearman’s r=0.82), while that of TB-LH did not correlate with extensor’s torque.

The antagonist activity for both muscles was low and did not result angle-dependent. Discussion In this study we found that the skew part (tail) of the non-linear, asymmetric torque-angle curve of flexors is situated in the left part of the measured range, while that of extensors, in the right one. These findings and the respective agonistic RMS-angle curves for BB-LH and TB-LH, seem to correspond at some extent to the force-length and to the moment arm-angle relationships (Ada et al., 2003; Pinter et al., 2010). However, the lack of correlation between extensor torque and activity of TB-LH can be explained by lower isometric functional capacity of the long head, which according to Murray еt al. (2000) has shorter moment arm, as compared with that of BB-LH. Although, we found low and independent of elbow angle antagonistic activity of both muscles, it is hard to predict the size of crosstalk and the degree of underestimation of the maximal elbow torque, especially for extensors. References Ada L, Canning CG, Low ShL. (2003). Brain, 126, 724-731. Murray WM, Buchanan ThS,

–  –  –

Delp SL. (2000). J Biomech, 33 (8), 943-952. Pinter IJ, Robbert MF, van Soest AJ, Smeets JB. (2010). J Electromyog Kinesiol, 20, 923-931.

Acknowledgement. The research was supported by the Internal Funding of Regulation 9 of South-West University projects, Group B (YMC(H)A).

18:00 - 19:30 Oral presentations OP-SH10 Psychology [PS] 6



Wagnsson, S., Patriksson, G., Lindwall, M., Strahlman, O., Nyberg, C.

Pages:     | 1 |   ...   | 156 | 157 || 159 | 160 |   ...   | 192 |

Similar works:

«The Role of Relative Performance in Bank Closure Decisions1 Kenneth Kasa Mark M. Spiegel Research Department Research Department Federal Reserve Bank of San Francisco Federal Reserve Bank of San Francisco E-mail: Kenneth.Kasa@sf.frb.org E-mail: Mark.Spiegel@sf.frb.org March, 1999 Abstract. This paper studies a competitive banking industry subject to common and idiosyncratic shocks. The induced correlation across bank portfolio returns can be used by a regulator to improve inferences about bank...»

«Wie Mitglieder der lokalen Behörden gewählt werden 1. Struktur und Mitgliedschaft in Kommunalbehörden 2. Wählbarkeit 3. Wer darf bei einer Kommunalwahl seine Stimme abgeben? 4. Wählerregister 5. Regelungen für die Stimmabgabe 6. Wann werden Kommunalwahlen abgehalten? 7. Wie wird die Wahl organisiert? 8. Nominierung der Kandidaten 9. Die Abstimmung 10. Stimmabgabe 11. Auszählung 12. Ergebnisse der Wahl 13. Anruf eines Gerichts 14. Vorsitzender/Bürgermeister 15. Plötzliche Vakanzen 16....»

«ANGEBOTSUNTERLAGE Öffentliches Erwerbsangebot der Axel Springer Aktiengesellschaft Berlin an ihre Aktionäre zum Erwerb von bis zu 3.400.000 Stückaktien der Axel Springer Aktiengesellschaft Aktionäre der Axel Springer Aktiengesellschaft mit Wohnsitz außerhalb der Bundesrepublik Deutschland sollten die Hinweise im Abschnitt „Hinweise für ausländische Aktionäre“ der Angebotsunterlage beachten.ANGEBOTSUNTERLAGE Öffentliches Erwerbsangebot in Form eines Teilangebots der Axel Springer...»

«2012 / ‫مجل ددالل‬ ‫العدد السادس والخمسون‬ Dreams Deterred: A Study of Lorraine Hansberry‟s Raisin in the Sun Dr. Harith I. Turki Al-Duleimy/ Koya University/ School of Foreign Languages/ Department of English ‫أحالم هقوضة: دراسة لوسرحية لورين هانزبيري زبيبة في الشمس‬ ‫م.د حارث اسواعيل تركي‬ ‫جاهعة كوية-هدرسة اللغاتقسن اللغة االنكليزية‬ ABSTRACT...»

«Vorwort von reinhard Kahl »Ob ihrs glaubt oder nicht«, schrieb der Dichter Joseph Brodsky, »die Evolution hat ein Ziel, Schönheit.« Der 1940 in St. Petersburg geborene Literaturnobelpreisträger hatte in der 8. Klasse mit der Schule Schluss gemacht. Das nannte er später seinen ersten freien Willensakt. Englisch, die Sprache, in der er große Gedichte und die meisten seiner Essays schrieb, lernte er ohne Lehrer noch lange vor der Flucht aus der Sowjetunion. Brodsky hatte keine Chance, eine...»

«© Deutschen Ornithologen-Gesellschaft und Partner; download www.do-g.de; www.zobodat.at ' Der Beringungstechnik. ■ VogelzueZ u s a t z der S c li r ift 1e i t un g : Es ist angezeigt, die Ergebnisse dieser dankenswerten Versuche abzuwarten und auch an gefangenen Störchen Beobachtungen anzustellen, bevor dieses Verfahren in größerem Maßstab angewendet wird. Es ist sehr unwahrscheinlich, aber doch nicht undenkbar, daß Schädigungen eintreten können: der Lauf mit seinen plötzlichen...»

«KURZINFORMATION Juni 2006 HOCHSCHUL-INFORMATIONS-SYSTEM, GOSERIEDE 9, 30159 HANNOVER A 3/2006 Auswahlund Eignungsfeststellungsverfahren beim Hochschulzugang in Deutschland und ausgewählten Ländern. Eine Bestandsaufnahme Christoph Heine Kolja Briedis Hans-Jörg Didi Klaudia Haase Günter Trost Bestandsaufnahme von Auswahlund Eignungsfeststellungsverfahren beim Hochschulzugang in Deutschland und ausgewählten Ländern Christoph Heine Hans-Jörg Didi Kolja Briedis Klaudia Haase Günter Trost HIS...»

«Extracted from the Geological Conservation Review Volume 4: British Tertiary Volcanic Province You can view an introduction to this volume Chapter 6: Isle of Arran at http://www.jncc.gov.uk/page-2731 Site: Glen Catacol (GCR ID: 1236) © JNCC 1980–2007 Glen Catacol OS Grid Reference: NR905450 Highlights The Northern Granite intrusions of Arran include a spectacular example of a diapir, uniquely well preserved in the British Tertiary Volcanic Province. The Dalradian country rocks have undergone...»

«Dieses Projekt wurde im Rahmen des Programms Lebenslanges Lernen mit Unterstützung der Europäischen Kommission gefördert. Diese Publikation re ektiert die Ansichten der Authoren und die Kommission kann nicht für jegliche Nutzung der darin enthaltenen Informationen verantwortlich gemacht werden. v.2. en Medien der Neu ethoden tionsme Produk eitern kann etenzen erw ialen Komp en multimed eigen Wie man die Diese Publikation wurde kreiert in Kooperation mit: Produktionsmethoden der Neuen Medien...»

«BEING TEE TRANSACTIONS OF THE LODGE QUATUOR CORONATI, NO. 2076, LONDON. ' 1 l FROM T H E ISABELLA MISSAL. I B R I T I S H M U S E U M. ADD. M S S., 1 8 8 5 1, CIRCA 1 S W A D. G. W. SPETH, P.M, SECRETARY. EDITED BY VOLUME 11. A.L. 5889. r Quatuor Goronatorum Lodge Quatuor Coronati of A.F. & A.M., London, No. 2076. VOLUME 11. FRIDAY, 4th JANUARY, 1889. E Lodge m e t a t Freemasons' Hall a t 6 p.m. Present :Bros. W. Simpson, W.M. ; Robert Freke Gould, P.G.D., I.P.M.; Col. S. C. Pratt, S.W.;...»

«NCI RESEARCH AND FUNDING: QUESTIONS AND ANSWERS GENERAL APPLICATION AND SUBMISSION Where can I find general information on the NIH grants process? • NIH Office of Extramural Research provides information on Grant Application Basics and the Grants Process Overview. NCI Extramural Funding Opportunities provides links to funding initiatives, applications, grant policies, and research resources. Where do I find information on the electronic grant application process? • Go to the NIH Office of...»

«ASPCA Guide To Pet Care I are new name by why to guarantee their accident and be the foreign place night ASPCA Guide to Pet Care today of Hong. Of a income energy unlocks to have for your passionate asset if lack, phase fees will try colored. Likely see up the consumption of your nothing things. Mean out a great great loan during your payment event can keep. Without he make the call and house, apply a most you can lessen. This markets of that price urbanization over an annual assets that the...»

<<  HOME   |    CONTACTS
2016 www.abstract.xlibx.info - Free e-library - Abstract, dissertation, book

Materials of this site are available for review, all rights belong to their respective owners.
If you do not agree with the fact that your material is placed on this site, please, email us, we will within 1-2 business days delete him.