{"id":2147,"date":"2023-11-30T12:17:11","date_gmt":"2023-11-30T12:17:11","guid":{"rendered":"https:\/\/staging.mikkelschleicher.dk\/?p=2147"},"modified":"2024-02-20T08:26:54","modified_gmt":"2024-02-20T07:26:54","slug":"bigger-muscles-less-flexible","status":"publish","type":"post","link":"https:\/\/mikkelschleicher.dk\/index.php\/2023\/11\/30\/bigger-muscles-less-flexible\/","title":{"rendered":"Do bigger muscles make you less flexible?"},"content":{"rendered":"

[et_pb_section fb_built=”1″ _builder_version=”4.23.1″ custom_padding=”0px||||false|false” global_colors_info=”{}”][et_pb_row _builder_version=”4.23.1″ background_size=”initial” background_position=”top_left” background_repeat=”repeat” custom_padding=”0px||||false|false” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.16″ custom_padding=”|||” global_colors_info=”{}” custom_padding__hover=”|||”][et_pb_text _builder_version=”4.23.1″ background_size=”initial” background_position=”top_left” background_repeat=”repeat” global_colors_info=”{}”]<\/p>\n

I find this question interesting because we often, myself included, assume a person is less flexible, if they happen to have a bigger build \u2013 however, it\u2019s not always the case. This is even though several studied have found a correlation between increased muscle mass and increased stiffness or reduced ROM (Neto et al. 2013; Ryan et al. 2009; Suga et al. 2021).<\/p>\n

One of the reasons why you can still be very flexible, even with a large amount of muscle, is that muscle morphology isn\u2019t the only factors that affect flexibility \u2013 another important factor is stretch tolerance, which I won\u2019t be getting more into here (Check out\u00a0this<\/a>\u00a0post if you want to read about the what happens when we get more flexible). It should also be noted that strength training can be an effective way of increasing flexibility (Afonso et al. 2021), even though you might increase muscle mass at the same time.<\/p>\n

In this post I\u2019ll be going over why an increase in muscle mass, might not always be bad for flexibility as well as give you some very basic pointers about how to approach strength training if you want to maintain or even increase flexibility through strength training.<\/p>\n

[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}”][et_pb_text _builder_version=”4.23.1″ background_size=”initial” background_position=”top_left” background_repeat=”repeat” global_colors_info=”{}”]To understand how changes in muscle mass might affect flexibility, we\u2019ll first need to go over some basic muscle anatomy.<\/p>\n

Skeletal muscles are made up of bundles of muscle fibers called fascicles, fascicles are made of bundles of myofibrils or muscle fibers (Jorgenson et al. 2020). Around the muscle fibers, there are layer of connective tissue \u2013 together with the muscle fibers, this makes the muscle work kind of like an elastic band when pulled, even when the muscle is relaxed.<\/p>\n

The fascicles can increase size in 2 ways; they can get thicker (this is called radial hypertrophy) \u2013 this would equate to getting a thicker elastic band \u2013 you\u2019ll need more force to stretch it out. This is why an increase in muscle mass, can affect flexibility negatively.<\/p>\n

Fascicles can also increase size by growing in length (this is called longitudinal hypertrophy). This would be the same as getting a longer elastic band. It\u2019s still as stiff, but it can be stretched further if we pull with the same amount of force. If the muscle mass is increased this way, it could have a positive effect on flexibility \u2013 Several studies have found that flexible individuals have longer fascicles compared with normal individuals (Blazevich et al. 2012; Moltubakk et al. 2018), while other have found a correlation between fascicle length and reduced passive resistance to stretch (Blazevich et al. 2007) and ROM in young males (Hirata et al. 2020).[\/et_pb_text][et_pb_image src=”https:\/\/mikkelschleicher.dk\/wp-content\/uploads\/2023\/11\/Fascicle.jpeg” title_text=”Fascicle” _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}”][\/et_pb_image][et_pb_text _builder_version=”4.23.1″ text_font_size=”10px” background_size=”initial” background_position=”top_left” background_repeat=”repeat” global_colors_info=”{}”]Figure 1: The whole muscle is made up of bundles of fascicles. Each fascicle is made up of myofibers, which we also call muscle fibers. [\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}”][et_pb_text _builder_version=”4.23.1″ background_size=”initial” background_position=”top_left” background_repeat=”repeat” global_colors_info=”{}”]Muscle size is often determined by measuring the Cross-Sectional area (CSA) of the muscle. It makes sense, that if the muscle fibers grows radially (become thicker), the CSA of the whole muscle also increases. However, depending on the structure of the muscle, an increase in fascicle length can also increase the CSA of the muscle (Jorgenson et al. 2020).<\/p>\n

Skeletal muscles can be structures in different way, in regards to how the muscle fibers are oriented in relation to the tendon. Overall, we can differ between muscles parallel muscles where the fibers are going more less straight from tendon to tendon (example A in figure 2) and pennate muscles, where the fibers are attached obliquely to the tendon (exambe B, C, and D in figure 2).[\/et_pb_text][et_pb_image src=”https:\/\/mikkelschleicher.dk\/wp-content\/uploads\/2023\/11\/Muscle-anatomy.jpeg” title_text=”Muscle-anatomy” _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}”][\/et_pb_image][et_pb_text _builder_version=”4.23.1″ text_font_size=”10px” background_size=”initial” background_position=”top_left” background_repeat=”repeat” global_colors_info=”{}”]Figure 2, from (Jorgenson et al. 2020) and (Orlandi D. 2015). (A) fusiform, (B) unipennate, (C) bipennante, (D) multipennate. Blue lines indicate the plane for the anatomical cross-sectional area (CSA) (i.e., the CSA that runs perpendicular to the longitudinal axis of the muscle), and green lines indicate the plane for physiological CSA (i.e., the CSA that runs perpendicular to the longitudinal axis of the fascicles\/myofibers).[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}”][et_pb_text _builder_version=”4.23.1″ background_size=”initial” background_position=”top_left” background_repeat=”repeat” global_colors_info=”{}”]Muscle size is often determined by measuring the Cross-Sectional area (CSA) of the muscle via ultrasound. In figure 1, the blue lines indicate the plane for the anatomical cross-sectional area (aCSA) (i.e., the CSA that runs perpendicular to the longitudinal axis of the muscle), and green lines indicate the plane for physiological CSA (pCSA) (i.e., the CSA that runs perpendicular to the longitudinal axis of the fascicles\/myofibers). If the muscle fibers grow radially (become thicker), the CSA of the muscle will increase \u2013 but in pennate muscles, an increase in fascicle length will also increase the aCSA of the muscle (Jorgenson et al. 2020).<\/p>\n

This is reflected in numerous studies that have found an association between whole muscle aCSA and fascicle length, among others a systematic review by Ryoichi Ema et al. (2016) that included data from 38 independent studies.
\nIt seems, that an increase in aCSA can be caused by both radial and longitudinal hypertrophy in pennate muscles.
\nAn increase in muscle aCSA caused solely by radial hypertrophy would have a negative effect on flexibility while an increase in muscle aCSA due to longitudinal hypertrophy, could have a positive effect on flexibility.<\/p>\n

So in parallel muscles, an increase in muscle size will most likely have a negative effect on flexibility. In pennate muscles, the effects of increasing muscle size on flexibility, will depend on the mechanism behind the hypertrophy, whether it\u2019s caused mostly by longitudinal or radial hypertrophy.<\/p>\n

If you want to strength train and grow bigger muscles without limiting your flexibility, it could be possible by maximizing hypertrophy through longitudinal hypertrophy. If you want to read more about how to increase flexibility through strength training, I wrote a blog post about this subject, that you can find here \u2013 but the main takeaway, is that you\u2019ll want to make sure to train your muscles at their longest range.[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}”][et_pb_text _builder_version=”4.23.1″ background_size=”initial” background_position=”top_left” background_repeat=”repeat” global_colors_info=”{}”]<\/p>\n

Referencer:<\/h4>\n

Afonso, J., R. Ramirez-Campillo, J. Mosc\u00e3o, T. Rocha, R. Zacca, A. Martins, A. A. Milheiro, J. Ferreira, H. Sarmento, and F. M. Clemente. 2021. \u201cStrength Training versus Stretching for Improving Range of Motion: A Systematic Review and Meta-Analysis.\u201d\u00a0Healthcare (Basel)<\/em>\u00a09 (4).\u00a0https:\/\/doi.org\/10.3390\/healthcare9040427<\/a>.<\/p>\n

Alegre, L. M., A. Ferri-Morales, R. Rodriguez-Casares, and X. Aguado. 2014. \u201cEffects of isometric training on the knee extensor moment-angle relationship and vastus lateralis muscle architecture.\u201d\u00a0Eur J Appl Physiol<\/em>\u00a0114 (11): 2437-46.\u00a0https:\/\/doi.org\/10.1007\/s00421-014-2967-x<\/a>.\u00a0https:\/\/www.ncbi.nlm.nih.gov\/pubmed\/25099962<\/a>.<\/p>\n

Blazevich, A. J., D. Cannavan, D. R. Coleman, and S. Horne. 2007. \u201cInfluence of concentric and eccentric resistance training on architectural adaptation in human quadriceps muscles.\u201d\u00a0J Appl Physiol (1985)<\/em>\u00a0103 (5): 1565-75.\u00a0https:\/\/doi.org\/10.1152\/japplphysiol.00578.2007<\/a>.\u00a0https:\/\/www.ncbi.nlm.nih.gov\/pubmed\/17717119<\/a>.<\/p>\n

Blazevich, A. J., D. Cannavan, C. M. Waugh, F. Fath, S. C. Miller, and A. D. Kay. 2012. \u201cNeuromuscular factors influencing the maximum stretch limit of the human plantar flexors.\u201d\u00a0J Appl Physiol (1985)<\/em>\u00a0113 (9): 1446-55.\u00a0https:\/\/doi.org\/10.1152\/japplphysiol.00882.2012<\/a>.\u00a0https:\/\/www.ncbi.nlm.nih.gov\/pubmed\/22923509<\/a>.<\/p>\n

Ema, R., T. Wakahara, N. Miyamoto, H. Kanehisa, and Y. Kawakami. 2013. \u201cInhomogeneous architectural changes of the quadriceps femoris induced by resistance training.\u201d\u00a0Eur J Appl Physiol<\/em>\u00a0113 (11): 2691-703.\u00a0https:\/\/doi.org\/10.1007\/s00421-013-2700-1<\/a>.\u00a0https:\/\/www.ncbi.nlm.nih.gov\/pubmed\/23949789<\/a>.<\/p>\n

Ema, Ryoichi, Ryota Akagi, Taku Wakahara, and Yasuo Kawakami. 2016. \u201cTraining-induced changes in architecture of human skeletal muscles: Current evidence and unresolved issues.\u201d\u00a0The Journal of Physical Fitness and Sports Medicine<\/em>\u00a05 (1): 37-46.\u00a0https:\/\/doi.org\/10.7600\/jpfsm.5.37<\/a>.<\/p>\n

Erskine, R. M., D. A. Jones, A. G. Williams, C. E. Stewart, and H. Degens. 2010. \u201cInter-individual variability in the adaptation of human muscle specific tension to progressive resistance training.\u201d\u00a0Eur J Appl Physiol<\/em>\u00a0110 (6): 1117-25.\u00a0https:\/\/doi.org\/10.1007\/s00421-010-1601-9<\/a>.\u00a0https:\/\/www.ncbi.nlm.nih.gov\/pubmed\/20703498<\/a>.<\/p>\n

Hirata, K., R. Yamadera, and R. Akagi. 2020. \u201cAssociations between Range of Motion and Tissue Stiffness in Young and Older People.\u201d\u00a0Med Sci Sports Exerc<\/em>\u00a052 (10): 2179-2188.\u00a0https:\/\/doi.org\/10.1249\/mss.0000000000002360<\/a>.<\/p>\n

Jorgenson, K. W., S. M. Phillips, and T. A. Hornberger. 2020. \u201cIdentifying the Structural Adaptations that Drive the Mechanical Load-Induced Growth of Skeletal Muscle: A Scoping Review.\u201d\u00a0Cells<\/em>\u00a09 (7).\u00a0https:\/\/doi.org\/10.3390\/cells9071658<\/a>.<\/p>\n

Kawakami, Y., T. Abe, S. Y. Kuno, and T. Fukunaga. 1995. \u201cTraining-induced changes in muscle architecture and specific tension.\u201d\u00a0Eur J Appl Physiol Occup Physiol<\/em>\u00a072 (1-2): 37-43.\u00a0https:\/\/doi.org\/10.1007\/BF00964112<\/a>.\u00a0https:\/\/www.ncbi.nlm.nih.gov\/pubmed\/8789568<\/a>.<\/p>\n

Magnusson, S. P., E. B. Simonsen, P. Aagaard, J. Boesen, F. Johannsen, and M. Kjaer. 1997. \u201cDeterminants of musculoskeletal flexibility: viscoelastic properties, cross-sectional area, EMG and stretch tolerance.\u201d\u00a0Scandinavian Journal of Medicine & Science in Sports<\/em>\u00a07 (4): 195-202.\u00a0https:\/\/doi.org\/https:\/\/doi.org\/10.1111\/j.1600-0838.1997.tb00139.x<\/a>.\u00a0https:\/\/onlinelibrary.wiley.com\/doi\/abs\/10.1111\/j.1600-0838.1997.tb00139.x<\/a>.<\/p>\n

Moltubakk, M. M., M. M. Magulas, F. O. Villars, O. R. Seynnes, and J. Bojsen-Moller. 2018. \u201cSpecialized properties of the triceps surae muscle-tendon unit in professional ballet dancers.\u201d\u00a0Scand J Med Sci Sports<\/em>\u00a028 (9): 2023-2034.\u00a0https:\/\/doi.org\/10.1111\/sms.13207<\/a>.\u00a0https:\/\/www.ncbi.nlm.nih.gov\/pubmed\/29723911<\/a>.<\/p>\n

Neto, T., S. Freitas, J. Vaz, A. M. Silva, P. Mil-Homens, and A. I. Carita. 2013. \u201cLower limb body composition is associated to knee passive extension torque-angle response.\u201d\u00a0Springerplus<\/em>\u00a02: 403.\u00a0https:\/\/doi.org\/10.1186\/2193-1801-2-403<\/a>.<\/p>\n

Orlandi D., Perugin Bernardi S. 2015.\u00a0Normal Anatomy and Biomechanics.<\/em>: Springer.<\/p>\n

Ryan, E. D., T. J. Herda, P. B. Costa, J. M. Defreitas, T. W. Beck, J. R. Stout, and J. T. Cramer. 2009. \u201cPassive properties of the muscle-tendon unit: the influence of muscle cross-sectional area.\u201d\u00a0Muscle Nerve<\/em>\u00a039 (2): 227-9.\u00a0https:\/\/doi.org\/10.1002\/mus.21218<\/a>.<\/p>\n

Suga, T., M. Terada, K. Tomoo, Y. Miyake, T. Tanaka, H. Ueno, A. Nagano, and T. Isaka. 2021. \u201cAssociation between plantar flexor muscle volume and dorsiflexion flexibility in healthy young males: ultrasonography and magnetic resonance imaging studies.\u201d\u00a0BMC Sports Sci Med Rehabil<\/em>\u00a013 (1): 8.\u00a0https:\/\/doi.org\/10.1186\/s13102-021-00233-z<\/a>.<\/p>\n

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Big muscles and flexibility are often seen as two things that don\u2019t combine. However, that\u2019s not always true \u2013an increase in muscle size can have a negative effect on flexibility, but it\u2019s not always the case<\/p>\n","protected":false},"author":1,"featured_media":2155,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"on","_et_pb_old_content":"

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Fleksibilitetstr\u00e6ning og styrketr\u00e6ning, bliver ofte set som to mods\u00e6tninger. Det er imidlertid ikke sandt, det er faktisk i h\u00f8j grad muligt at kombinere fleksibilitet og styrketr\u00e6ning. Det kan endda have visse fordele hvis man gerne vil v\u00e6re mere fleksibel, sammenlignet med traditionel udstr\u00e6kning.<\/p>

I denne artikel vil jeg pr\u00e6sentere dig for de fordele der findes ved at tr\u00e6ne fleksibilitet gennem styrketr\u00e6ning, samt hvordan denne type tr\u00e6ning p\u00e5virker fleksibiliteten, med udgangspunkt i den videnskabelige litteratur p\u00e5 omr\u00e5det.
I sidste del af artiklen, vil jeg komme med anbefalinger ift. hvordan du selv kan tr\u00e6ne fleksibilitet p\u00e5 denne m\u00e5de. Denne del bygger p\u00e5 den viden der pr\u00e6senteres i f\u00f8rste del, men ogs\u00e5 p\u00e5 personlig erfaring.<\/p>

I fleksibilitetstr\u00e6ning skelnes der mellem aktiv og passiv, samt dynamisk og statisk[1]. Aktiv fleksibilitetstr\u00e6ning inkluderer en form for volunt\u00e6r kontraktion af den forl\u00e6ngede eller forkortede muskel, men passiv fleksibilitetstr\u00e6ning foreg\u00e5r uden[2].
Statisk udstr\u00e6kning er den form de fleste af os kender, hvor man holder et str\u00e6k. Navnet siger n\u00e6sten sig selv, det er statisk udstr\u00e6kning, alts\u00e5 uden bev\u00e6gelse. Dynamisk udstr\u00e6kning d\u00e6kker alle former for udstr\u00e6kning hvor man bev\u00e6ger sig ind og ud af et str\u00e6k. N\u00e5r fleksibilitet tr\u00e6nes gennem styrketr\u00e6ning, kan det g\u00f8res som en form for dynamisk udstr\u00e6kning, hvor bev\u00e6gelsen ind og ud af et str\u00e6k, organiseres i s\u00e6t og gentagelser, eller gennem isometrisk styrketr\u00e6ning, der kan sidestilles med statisk udstr\u00e6kning.<\/p>

N\u00e5r man \u00f8ger sin fleksibilitet, sker det enten ved at noget v\u00e6v forl\u00e6nges (muskler, sener, bindev\u00e6v, etc.), eller ved at den sensoriske oplevelse af str\u00e6kket \u00e6ndres, s\u00e5dan at evnen til at tolerere f\u00f8lelsen af str\u00e6k \u00f8ges. N\u00e5r str\u00e6k tolerancen \u00f8ges, betyder det, at det f\u00f8les mindre intenst\/smertefuldt i bev\u00e6ge sig ind i et str\u00e6k, hvilket g\u00f8r at man kan bev\u00e6ge sig dybere ind i det og fleksibiliteten \u00f8ges [6]. Studier af 6-8 uger varighed, der unders\u00f8ger effekten af statisk udstr\u00e6kning, finder at den \u00f8gede fleksibilitet der opn\u00e5s, udelukkende sker p\u00e5 baggrund af \u00f8get str\u00e6k tolerance [6][13]. Der er lavet f\u00e5 studier der unders\u00f8ger den l\u00e6ngerevarende effekt af statisk udstr\u00e6kning, men et studie af Moltubakk (2019)[14], tyder p\u00e5 at der efter 24 ugers udstr\u00e6kning forekommer visse strukturelle adaptation.<\/p>

Styrketr\u00e6ning kan som sagt anvendes til at tr\u00e6ne fleksibilitet. B\u00e5de excentrisk[3], men ogs\u00e5 konventionel styrketr\u00e6ning[4] kan \u00f8ge fleksibilitet, hvis de tr\u00e6nede bev\u00e6gelser laves med fuld ROM [15]. Den \u00f8gede fleksibilitet, der forekommer ved denne form for tr\u00e6ning, kan forklares dels ved en \u00f8get str\u00e6k tolerance, dels ved strukturelle \u00e6ndringer, i form af \u00f8get fascikel l\u00e6ngde, sandsynligvis p\u00e5 grund af sarkomerogenese[5].
En fascikel er et lille bundt af muskelfibre. Sarkomerogenese er en proces hvor antallet af sarkomerer i forl\u00e6ngelse af hinanden, \u00f8ges i en muskelfiber. Biomekanisk har det betydning at der sker p\u00e5 netop denne m\u00e5de, men oversat til normalt sprog, betyder det bare at muskelfiberen bliver l\u00e6ngere. Dog med den \u201cbonus\u201d, at musklens kraftkurve samtidig forskydes, s\u00e5ledes at musklen bliver st\u00e6rkere i en mere forl\u00e6nget position.
Det reducerer risikoen for visse muskelskader, s\u00e5som fiberspr\u00e6ngninger[9]. Ved meget intens udstr\u00e6kning kan man risikere at f\u00e5 forstr\u00e6kninger, men ogs\u00e5 her vil excentrisk fleksibilitetstr\u00e6ning h\u00f8jst sandsynligt reducere risikoen. Almindelig passiv udstr\u00e6kning derimod, ser ikke ud til at have nogen effekt p\u00e5 risikoen for skader [10].<\/p>

Effekten af passiv udstr\u00e6kning ser ud til hovedsageligt at v\u00e6re \u00f8get str\u00e6ktolerance[6], og potentielt strukturelle \u00e6ndringer ved lang tids tr\u00e6ning. Enkelte studier har ogs\u00e5 fundet \u00f8get fascikel l\u00e6ngde efter udstr\u00e6kning med meget h\u00f8j intensitet og\/eller volumen.
Styrketr\u00e6ning af muskulaturen i en forl\u00e6nget position, ser imidlertid ud til at f\u00f8re til \u00f8get str\u00e6k tolerance, i samme grad som passivt str\u00e6k[7], men kan ogs\u00e5 f\u00f8re til strukturelle adaptationer, allerede efter 5-8 ugers tr\u00e6ning. Derudover ser det ud til at man i h\u00f8j grad kan bibeholde de strukturelle \u00e6ndringer(alts\u00e5 de l\u00e6ngere fascikler\/muskler) der sker som f\u00f8lge af styrketr\u00e6ning som fleksibilitetstr\u00e6ning, selv efter at man stopper med at tr\u00e6ne[8]. Styrketr\u00e6ning og statisk udstr\u00e6kning, ser ud til at v\u00e6re lige effektive n\u00e5r det kommer til at \u00f8ge bev\u00e6geudslag\/ROM [16], men at tr\u00e6ne fleksibilitet gennem styrketr\u00e6ning, har de fordele, at du samtidigt bliver st\u00e6rkere, mindsker risikoen for visse typer af skader og sandsynligvis kan beholde dine fleksibilitets gains i l\u00e6ngere tid, efter du stopper med at tr\u00e6ne.<\/p>

Herunder opsummeres pointerne fra f\u00f8rste del:<\/strong><\/p>