Aalborg Universitet. Muscle synergies during bench press Kristiansen, Mathias Vedsø - PDF

Description
Aalborg Universitet Muscle synergies during bench press Kristiansen, Mathias Vedsø DOI (link to publication from Publisher): /vbn.phd.med Publication date: 2015 Document Version Final published

Please download to get full document.

View again

of 36
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Information
Category:

Music

Publish on:

Views: 16 | Pages: 36

Extension: PDF | Download: 0

Share
Transcript
Aalborg Universitet Muscle synergies during bench press Kristiansen, Mathias Vedsø DOI (link to publication from Publisher): /vbn.phd.med Publication date: 2015 Document Version Final published version Link to publication from Aalborg University Citation for published version (APA): Kristiansen, M. V. (2015). Muscle synergies during bench press. Aalborg Universitetsforlag. (Ph.d.-serien for Det Sundhedsvidenskabelige Fakultet, Aalborg Universitet). DOI: /vbn.phd.med General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.? Users may download and print one copy of any publication from the public portal for the purpose of private study or research.? You may not further distribute the material or use it for any profit-making activity or commercial gain? You may freely distribute the URL identifying the publication in the public portal? Take down policy If you believe that this document breaches copyright please contact us at providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from vbn.aau.dk on: March 12, 2017 MUSCLE SYNERGIES DURING BENCH PRESS BY MATHIAS KRISTIANSEN DISSERTATION SUBMITTED 2015 MUSCLE SYNERGIES DURING BENCH PRESS Ph.D Thesis by Mathias Kristiansen, B.Sc., M.Sc. DISSERTATION SUBMITTED TO DEPARTMENT OF HEALTH SCIENCE AND TECHNOLOGY AT AALBORG UNIVERSITY Thesis submitted: October 2, 2015 PhD supervisor: Associate Prof. Ernst Albin Hansen Aalborg Universi Assistant PhD supervisors: Prof. Pascal Madeleine Aalborg University Associate Prof. Afshin Samani, Aalborg University PhD committee: Associate Professor, PhD Jesper Franch (chairman) Aalborg University Dr. Jonathan Paul Folland Loughborough University Dr. Francois Hug University of Nantes PhD Series: Faculty of Medicine, Aalborg University ISSN (online): ISBN (online): Published by: Aalborg University Press Skjernvej 4A, 2nd floor DK 9220 Aalborg Ø Phone: forlag.aau.dk Copyright: Mathias Vedsø Kristiansen Printed in Denmark by Rosendahls, 2015 CURRICULUM VITAE PhD thesis title: PhD Student: Supervisor: Co-supervisors: Muscle synergies during bench press Mathias Kristiansen Associate Prof. Ernst Albin Hansen, Prof. Pascal Madeleine and Associate Prof. Afshin Samani List of published/submitted articles: I. Kristiansen, M., Samani, A., Madeleine, P., Hansen, E. A. Muscle synergies during bench press are reliable across days. Journal of electromyography and kinesiology, in revision. II. Kristiansen, M., Madeleine, P., Hansen, E. A., Samani, A Inter-subject variability of muscle synergies during bench press in power lifters and untrained individuals. Scandinavian Journal of Medicine and Science in Sports, 25, 1, III. Kristiansen, M., Samani, A., Madeleine, P., Hansen, E. A. Effects of five weeks of bench press training on muscle synergies A randomized controlled study. Journal of strength and conditioning research, in revision. III MUSCLE SYNERGIES DURING BENCH PRESS ENGLISH SUMMARY Strength training, in various forms, is a widely practiced form of physical training. It is generally thought that both morphological mechanisms and neurological mechanisms play a role in the increase in strength following training. As the human body represents a linked mechanical system, postural activity specific to the task, bracing, and proper setup of a base of support, is critical for the expression of maximal strength. Thus, the precise activation and timing of agonist, synergist, and antagonist muscles is of paramount importance to forceful execution of the task at hand. This can be referred to as inter-muscular coordination. The general aim of this thesis was to provide further insight into inter-muscular coordination during bench press. This aim was pursued by investigating the reliability of inter-muscular coordination, differences in inter-muscular coordination between groups of different training status, and the effects of upper-body strength training on intermuscular coordination. For that purpose, muscle synergies were extracted from electromyography data recorded during submaximal bench press by means of nonnegative matrix factorization. Currently, there is a lack of knowledge regarding the reliability of muscle synergy extraction, and the effects of various training modalities on muscle synergies. In Study (I), the between-day reliability of extracting muscle synergies during bench press was assessed and found to be strong to very strong. In Study (II), a cross-sectional study design was used to asses if differences in muscle synergies reside in subject groups of very different training status. Expert powerlifters were found to exhibit larger inter-subject variability in the synergy activation coefficient and less inter-subject variability in the muscle synergy vectors responsible for the concentric phase of the bench press, compared to untrained subjects. In Study (III), a randomized controlled trial was carried out in an attempt to establish a causal relationship between training and alterations in muscle synergies. Performing a cross-validation test of the extracted muscle synergies, revealed that changes had occurred in the muscle synergies of the group that performed strength training for five weeks, while no changes had occurred in the control group. The present thesis provided novel data on the between-day reliability of muscle synergies. Further, it was documented that distinct differences in muscle synergies were present between expert powerlifters and untrained subjects, and that five weeks of strength training induced changes in muscle synergies during bench press. IV DANSK RESUMÉ Styrketræning i forskellige former er en meget udbredt form for fysisk træning. Den generelle opfattelse er at en øgning i styrke som følge af styrketræning, er forårsaget af både morfologiske og neurologiske mekanismer. Da den menneskelige krop repræsenterer et forbundet mekanisk system, betyder det at specifik postural aktivitet og opspænd er kritisk i forhold at udøve maksimal kraft. Det vil sige at den præcise aktivering og timing af agonist, synergist, og antagonist muskulatur er af afgørende betydning for udviklingen af kraft i en given øvelse. Dette samspil mellem musklerne, kaldes for inter-muskulær koordination. Det overordnede mål for denne PhD afhandling var at opnå yderligere indsigt i den inter-muskulære koordination ved øvelsen bænkpres. Dette blev gjort ved at undersøge pålideligheden af inter-muskulær koordination, forskellen i inter-muskulær koordination imellem grupper af forskellig træningsstatus, og effekten af styrketræning på inter-muskulær koordination. For at opnå dette blev der udtrukket muskel synergier fra elektromyografisk data, der var blevet optaget ved submaksimal bænkpres, ved brug af en nonnegativ matrix factorization algoritme. Generelt mangler der viden vedrørende pålideligheden af muskel synergier og trænings effekt på muskel synergier. I studie (I), blev pålideligheden af muskel synergier under bænkpres vurderet til at være stærk til meget stærk. I studie (II), blev et tværsnits studiedesign anvendt til at undersøge forskellen i muskel synergier for to grupper med meget forskellig træningserfaring. Her blev det vist at styrkeløftere på eliteniveau, udviste større variabilitet i den synergi aktiverings koefficient, og mindre variabilitet i de muskler synergi vektorer, som repræsenterede den koncentriske fase i bænkpres, end de forsøgspersoner som var utrænede. I studie (III), blev der udført et randomiseret kontrolleret forsøg, med det mål at etablere at kausalt forhold mellem træning og ændringer i muskel synergier. Udførelsen af en kryds-valideringstest resulterede i at der var sket ændringer i muskel synergierne hos den gruppe som udførte styrketræning i fem uger, hvorimod der ingen ændringer var sket i kontrol gruppen. Denne afhandling præsenterer nye resultater vedrørende pålideligheden af muskel synergier. Endvidere dokumenteres det at der er tydelig forskel i muskel synergier for styrkeløftere på eliteniveau og utrænede, og at fem ugers styrketræning kan inducere ændringer i muskel synergier under bænkpres. V MUSCLE SYNERGIES DURING BENCH PRESS ACKNOWLEDGEMENTS Completion of the current thesis would not have been possible without the generous economic support of: The Ministry of Culture Committee on Sports Research in Denmark, The Danish Rheumatism Association, Danish Council for Independent Research Technology and Production Sciences (FTP), and Otto Mønsted Fonden. I also wish to thank Aalborg Sportshøjskole for loan of the lifting equipment used during data collection for Study (II). Similarly, I wish to thank Erik Rasmussen from ER-Equipment, for his generous sponsorship of the lifting equipment used during data collection of Study (I) and (III). Furthermore, I would like to acknowledge the support and encouragement that I have received from my supervisors. I would like to thank: Ernst Albin Hansen, for his bluntly feedback, irrepressible perfectionism and superb guidance. Pascal Madeleine, for his supreme project leadership skills, ability to see one step ahead, and vast high level scientific experience. And Afshin Samani, for his excellent technical and mathematical support and guidance, as well as his hard working ethics. I have gained a tremendous amount of knowledge and experience from working with you all, and for this I am truly thankful. Last but not least, I would like to acknowledge the love and support I have received from friends and family. Especially, I would like to thank my wife Louise, for her endless support, encouragement and belief in me. This would not have been possible without you. VI PREFACE The present studies were carried out in the period 2012 to 2015 at the Physical Activity and Human Performance group, SMI, Department of Health Science and Technology, Aalborg University, Denmark. The current PhD stipend was funded by Aalborg University. The thesis is based on the following three articles. In the text these are referred to as Study (I), Study (II), and Study (III) (full-length articles in Appendix). Study (I): Kristiansen, M., Samani, A., Madeleine, P., Hansen, E. A. Muscle synergies during bench press are reliable across days. Journal of electromyography and kinesiology, in revision. Study (II): Kristiansen, M., Madeleine, P., Hansen, E. A., Samani, A Inter-subject variability of muscle synergies during bench press in power lifters and untrained individuals. Scandinavian Journal of Medicine and Science in Sports, 25, 1, Study (III): Kristiansen, M., Samani, A., Madeleine, P., Hansen, E. A. Effects of five weeks of bench press training on muscle synergies A randomized controlled study. Journal of strength and conditioning research, in revision. This thesis has been submitted for assessment in partial fulfilment of the PhD degree. The thesis is based on the submitted or published scientific articles which are listed above. Parts of the articles are used directly or indirectly in the extended summary of the thesis. As part of the assessment, co author statements have been made available to the assessment committee and are also available at the Faculty. The thesis is not in its present form acceptable for open publication but only in limited and closed circulation as copyright may not be ensured. VII TABLE OF CONTENTS Curriculum vitae... iii English summary... iv Dansk resumé... v Acknowledgements... vi Preface...vii List of abbreviations Introduction Strength training in general Adaptations to strength training Redundancy of the musculoskeletal system Muscle synergies as a framework for motor control Extracting muscle synergies using nonnegative matrix factorization Aims of the PhD project Methods Subjects (Study I-III) Strength testing (Study I-III) Data collection (Study I-III) Normalization of the time scale (Study I-III) Electromyographic recordings (Study I-III) EMG data processing Normalization of EMG Nonnegative matrix factorization (Study I-III) Variance accounted for Functional sorting Cross-validation of muscle synergies (Study I-III) Strength training protocol (Study III) Statistics Results MUSCLE SYNERGIES DURING BENCH PRESS 3.1 Strength (Study I-III) Variance accounted for (VAF) Muscle synergies (Study I-III) Reliability of muscle synergies (Study I) Effect of expertise on muscle synergies (Study II) Effect of strength training on muscle synergies (Study III) Discussion Strength VAF and number of muscle synergies Reliability of muscle synergies (Study I) Effect of expertise on muscle synergies (Study II) Effect of strength training on muscle synergies (Study III) Methodological considerations Strengths and limitations Conclusions Perspectives Thesis at a glance References Appendices 1. INTRODUCTION LIST OF ABBREVIATIONS 3RM C C Pre_FixW C Post_FixW C prew-postw C prew-prefixw C postw-postfixw CC prec-postc CC prec-prefixc CC postc-postfixc CON e E EMG EXP ICC 3,1 SEM SD TRA UNT VAF VAF Fix_A VAF Fix_V VAF Fix_W VAF Fix_C VAF muscle W W Pre_FixC W Post_FixC ρ max r max t max : Three repetition maximum : Synergy activation coefficient : Recomputed synergy activation coefficient for pretest : Recomputed synergy activation coefficient for posttest : Correlation of muscle synergy vectors from the pretest and posttest : Correlation of the original and the recomputed muscle synergy vectors from the pretest : Correlation of the original and the recomputed muscle synergy vectors from the posttest : Cross-correlation of synergy activation coefficients from the pretest and posttest : Cross-correlation of the original and the recomputed synergy activation coefficients from the pretest : Cross-correlation of the original and the recomputed synergy activation coefficients from the posttest : Control group, Study (III) : Residual error matrix : Initial matrix : Electromyography : Expert powerlifter group, Study (II) : Intraclass correlation coefficient : Standard error of measurement : Standard deviation : Training group, Study (III) : Untrained subject group, Study (II) : Variance accounted for : Recomputed VAF by fixing the synergy activation coefficient, Study (I) : Recomputed VAF by fixing the muscle synergy vector, Study (I) : Recomputed VAF by fixing the muscle synergy vector, Study (III) : Recomputed VAF by fixing the synergy activation coefficient, Study (III) : Variance accounted for of an individual muscle : Muscle synergy vector : Recomputed muscle synergy vector for pretest : Recomputed muscle synergy vector for posttest : Maximum Spearman cross-correlation value : Maximum Pearson cross-correlation value (r-value) : Lag time, taken when the correlation value is maximal 11 1 INTRODUCTION 1.1 STRENGTH TRAINING IN GENERAL Strength training, in various forms, is a widely practiced form of physical training (19). Strength training is a key component in developing athletic performance (87), in which power output, agility, and reaction time are important parameters. In addition, strength training may also be used as an important part of injury prevention. For instance, specific strength training may counteract muscle strength imbalances. Such imbalances in thigh and hip muscle strength can be predictive of an increased risk of hamstring injury in elite-level Australian football players (10) and adductor muscle strains in professional ice hockey players (80), respectively. Strength training may also serve to combat age-induced declines in muscle strength and function, as elderly also have been shown to respond very well to strength training (22, 60). In particular for the elderly population, maintenance of strength is a key component in the ability to perform normal activities of daily living. Consequently, a decline in strength among elderly individuals has a major impact on their ability to maintain an independent lifestyle, causes physical frailty (20), and induces an increased risk of fall related injuries (85). As described above, the positive effects of strength training are numerous and the practical applications are widespread, underlining the importance of a deeper understanding of the underlying mechanisms responsible for increase and maintenance of strength. 1.2 ADAPTATIONS TO STRENGTH TRAINING Overall, the mechanisms responsible for the expression of muscular strength levels may be divided into two categories; morphological mechanisms and neurological mechanisms (19). It is generally regarded that the primary morphological adaptation resulting from prolonged strength training, is skeletal muscle hypertrophy. Therefore, muscle hypertrophy following strength training has been widely documented (33, 52). However, during the early stages of a strength training program, only relatively small increases in muscle hypertrophy can be observed (59), whereas strength will typically increase to a much greater extent (24, 44). This creates a mismatch in the time course of strength gain and muscle hypertrophy, as the increase in strength is much higher than what can be explained by the significant, but very small increase in muscle mass. Consequently, the sole increase in muscle hypertrophy cannot account alone for the increase in strength, suggesting that neurological adaptations must play an important role in the expression of strength. 13 MUSCLE SYNERGIES DURING BENCH PRESS The neurological mechanisms responsible for increases in strength involve both intra-muscular adaptations and inter-muscular adaptations. Several studies have investigated intra-muscular adaptations following strength training. For instance, strength training has been shown to cause an increase in neural drive (1, 23, 70, 84), motor unit firing rate (34, 58), and motor unit synchronization (66) within the agonist muscles. Intuitively, a larger activation of agonist muscles, caused by changes in descending drive, should result in a higher force output, all other things being equal. However, strength is often expressed through the use of multi-joint free weight exercises. In such a setting, the increased force producing capabilities of agonist muscles are not the only important parameter necessary to produce adequate task performance. As the human body represents a linked mechanical system, postural orientation and postural equilibrium are two important factors that must be controlled prior to execution of forceful task (26). Therefore, bracing and postural activity specific to the task are critical for the expression of maximal strength and have thus been shown to adapt following strength training (62). Further, the adaptations in strength have been shown to be highly specific to the postures utilized in training (86). Thus, the precise activation and timing of agonist, synergist, and antagonist muscles are of paramount importance to forceful execution of the task at hand (64). This means that the expression of maximal strength can be viewed as a skilled act, in which the coordination of all the taskrelevant muscles must be learned, trough practice. This skilled and learned act can be referred to as inter-muscular coordination. The literature on adaptations in intermuscular coordination following strength training is rather limited, and has primarily been concentrated on studying the agonist-antagonist relationship during single joint movements. It has thus been shown that strength training may cause an increased coactivation of synergist muscles and a reduced coactivation of antagonist muscles (12, 22). In general, single joint exercises are considered to be simple, and only to a lesser extent influenced by the skill of the subject. However, it has been shown that during submaximal isometric contractions of the knee extensor muscles, subjects adopted various strateg
Related Search
Similar documents
View more...
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks