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Created page with "Muscles play an obvious role in running, and understanding the different muscle types and recruitment patterns can help us optimize training techniques. =Muscle Fiber Types= ..."
Muscles play an obvious role in running, and understanding the different muscle types and recruitment patterns can help us optimize training techniques.
=Muscle Fiber Types=
Skeletal muscle fibers vary in their characteristics, and there are several different ways of categorizing them. While a simple categorization is appealing, in reality fibers tend to vary in multiple ways, so remember that while this is a useful model, [[All models are wrong]]. This is a little like classifying cars into different types. You can categorize cars based on the number of doors, how fast they are, what shape the back is, etc. The table below shows several classification systems and the characteristics of the fibers<ref name="Scott-2001"/>.
{| class="wikitable"
! colspan="5"|Categorization
! colspan="2"|Characteristics
|-
| '''Contraction speed'''
| '''Myosin ATPase'''
| '''Myosin heavy chain'''
| '''Biochemical'''
| '''Motor Unit Classification'''
| '''Resistance to fatigue'''
| '''Force Generated'''
|-
| Slow Twitch
| Type I
| MHCI
| Slow Twitch Oxidative (SO)
| Slow Twitch Fatigue Resistant
| High
| Low
|-
| rowspan="2"| Fast Twitch
| Type IIa
| MHCIIa
| Fast Twitch Oxidative/Glycolytic (FOG)
| Fast Twitch Fatigue Resistant
| Medium
| Medium
|-
| Type IIb
| MHCIIx/d
| Fast Twitch Glycolytic (FG)
| Fast Twitch Fatigable
| Low
| High
|}
==Notes==
* There is a good correlation between type I and SO fibers, but the correlations between type IIA and FOG and type IIB and FG fibers are not so clear<ref name="Hämäläinen-1995"/>.
* In addition to those shown in the table, mATPase also has IC, IIC, IIAC, IIAB types that are not shown<ref name="Staron-1997"/>.
* The original Myosin heavy chain classification of MHCIIb in humans now appears to be the MHCIIx/MHCIId type found in small mammals<ref name="Hilber-1999"/>, and humans do not actually have the MHCIIb form<ref name="Pette-1999"/>.
[[File:Muscle Fiber Classification.jpg|none|thumb|500px|This is a picture visualizes some of the ways of categorizing muscle fibers.]]
==Fiber Type Plasticity==
There is overwhelming evidence that fibers can change type, with transitions between Type IIa and Type IIb being the most common<ref name="PetteStaron1997"/>. Conversion between Type I and Type II has been shown to occur with severe deconditioning, such as spinal injury<ref name="Roy-1999"/>. The only evidence of transitions from Type II to Type I with training is limited to studies of denervated muscles that were electrically stimulated for weeks<ref name="Eken-1988"/>. In rats, the transformation occurred sequentially as type IIB/IIX to type IIA to type I, with the type IIB/IIX to type IIA occurring after 2 weeks and the type IIA to type I taking longer than 2 months<ref name="WindischGundersen1998"/>.
=Muscle Recruitment=
We control our muscles so that we can lift a heavy weight or gently lift a cup of coffee. Our muscles are made up of many small fibers, and when we use less than our full strength we activate just some of those fibers<ref name="SkeletalMuscle"/>. So lifting the cup of coffee might only use a few of the fibers, but those fibers are fully activated. Each muscle fiber is either generating force or not; there is no in-between. Some muscle fiber types are more easily recruited, and the order is Type I, Type IIa, and finally Type IIb <ref name="MacIntoshGardiner2006"/>.This can be seen in the patterns of [[Glycogen]] depletion. Muscle recruitment has some important implications for training methods. To train all our muscle fibers we either have to generate the maximum force our muscles can produce or we have to exhaust some fibers so that others are activated in their place.
==Endurance Training==
Here's an analogy for muscle recruitment patterns while running long distances. Imagine each muscle fiber is a person and the long run is a war. Initially, the highly trained troops are the first to be deployed. When these highly trained troops become fatigued, then the reserve troops are called in to replace them. Eventually even the reserve troops become fatigued, and the draft calls in anyone who is able bodied. If things go on long enough, then the old men and children have to fight. In the same way we rely on a few well-trained muscle fibers early on in a run. As these muscle fibers become fatigued, we call on less well trained fibers. Thus as the training run progresses we work our way through the various muscle fibers. This is why a 15 mile training run does not provide 75% of the endurance benefit of a 20 mile run.
==Maximum Strength Training==
Lifting heavy weights requires engaging more of the muscle fibers. Maximum strength training has been shown to improve [[Running Economy]] without changing [[VO2max|V̇O<sub>2</sub>max]]<ref name="Støren-2008"/><ref name="Johnson-1997"/><ref name="Millet-2002"/>. Improvements in endurance have also been seen with elite level cyclists undergoing maximum strength training (5-6 reps to failure)<ref name="AagaardAndersen2010"/>.
==Plyometrics==
Plyometrics use explosive exercises where the full strength of the muscles are engaged for a short period of time. Preceded a muscle contraction with muscle extension under load generates maximum muscle engagement. An example of this can be seen in box jumps, where you jump down from a box and then immediately jump back up. The jumping down extends the muscles under load (eccentric exercise) which then helps generate more force on the jump back up. Like Maximum strength training, plyometrics improve [[Running Economy]] and performance without changing [[VO2max|V̇O<sub>2</sub>max]]<ref name="Paavolainen-1999"/><ref name="Turner-2003"/><ref name="SpurrsMurphy2003"/><ref name="Spurs-2002"/>. Plyometrics have also been shown to improve neuromuscular control for running that follows cycling, such as occurs during triathlons<ref name="BonacciGreen2011"/>.
=References=
<references>
<ref name="BonacciGreen2011">Jason Bonacci, Daniel Green, Philo U. Saunders, Melinda Franettovich, Peter Blanch, Bill Vicenzino, Plyometric training as an intervention to correct altered neuromotor control during running after cycling in triathletes: A preliminary randomised controlled trial, Physical Therapy in Sport, volume 12, issue 1, 2011, pages 15–21, ISSN [http://www.worldcat.org/issn/1466853X 1466853X], doi [http://dx.doi.org/10.1016/j.ptsp.2010.10.005 10.1016/j.ptsp.2010.10.005]</ref>
<ref name="Spurs-2002">Plyometric training improves distance running performance: A case study, Journal of Science and Medicine in Sport, volume 5, issue 4, 2002, pages 41, ISSN [http://www.worldcat.org/issn/14402440 14402440], doi [http://dx.doi.org/10.1016/S1440-2440(02)80117-7 10.1016/S1440-2440(02)80117-7]</ref>
<ref name="SpurrsMurphy2003">Robert W. Spurrs, Aron J. Murphy, Mark L. Watsford, The effect of plyometric training on distance running performance, European Journal of Applied Physiology, volume 89, issue 1, 2003, pages 1–7, ISSN [http://www.worldcat.org/issn/1439-6319 1439-6319], doi [http://dx.doi.org/10.1007/s00421-002-0741-y 10.1007/s00421-002-0741-y]</ref>
<ref name="Turner-2003"> AM. Turner, M. Owings, JA. Schwane, Improvement in running economy after 6 weeks of plyometric training., J Strength Cond Res, volume 17, issue 1, pages 60-7, Feb 2003, PMID [http://www.ncbi.nlm.nih.gov/pubmed/12580657 12580657]</ref>
<ref name="AagaardAndersen2010">P. Aagaard, J. L. Andersen, Effects of strength training on endurance capacity in top-level endurance athletes, Scandinavian Journal of Medicine & Science in Sports, volume 20, 2010, pages 39–47, ISSN [http://www.worldcat.org/issn/09057188 09057188], doi [http://dx.doi.org/10.1111/j.1600-0838.2010.01197.x 10.1111/j.1600-0838.2010.01197.x]</ref>
<ref name="Paavolainen-1999"> L. Paavolainen, K. Häkkinen, I. Hämäläinen, A. Nummela, H. Rusko, Explosive-strength training improves 5-km running time by improving running economy and muscle power., J Appl Physiol, volume 86, issue 5, pages 1527-33, May 1999, PMID [http://www.ncbi.nlm.nih.gov/pubmed/10233114 10233114]</ref>
<ref name="Millet-2002"> GP. Millet, B. Jaouen, F. Borrani, R. Candau, Effects of concurrent endurance and strength training on running economy and .VO(2) kinetics., Med Sci Sports Exerc, volume 34, issue 8, pages 1351-9, Aug 2002, PMID [http://www.ncbi.nlm.nih.gov/pubmed/12165692 12165692]</ref>
<ref name="Johnson-1997"> Johnson, Ronald E., et al. "Strength training in female distance runners: impact on running economy." The Journal of Strength & Conditioning Research 11.4 (1997): 224-229.</ref>
<ref name="Støren-2008"> O. Støren, J. Helgerud, EM. Støa, J. Hoff, Maximal strength training improves running economy in distance runners., Med Sci Sports Exerc, volume 40, issue 6, pages 1087-92, Jun 2008, doi [http://dx.doi.org/10.1249/MSS.0b013e318168da2f 10.1249/MSS.0b013e318168da2f], PMID [http://www.ncbi.nlm.nih.gov/pubmed/18460997 18460997]</ref>
<ref name="MacIntoshGardiner2006">Brian R. MacIntosh !!author1!!, Phillip F. Gardiner !!author2!!, Alan J. McComas !!author3!!, Skeletal Muscle: Form And Function, Accessed on 13 April 2013, 2006, publisher Human Kinetics 1, isbn 978-0-7360-4517-9, pages 201–</ref>
<ref name="SkeletalMuscle"> Brian R. MacIntosh, Phillip F. Gardiner, Alan J. McComas, Skeletal muscle : form and functio, date 2006, publisher Human Kinetics, location Champaign, IL, isbn 0736045171</ref>
<ref name="WindischGundersen1998">A. Windisch, K. Gundersen, M. J. Szabolcs, H. Gruber, T. Lomo, Fast to slow transformation of denervated and electrically stimulated rat muscle, The Journal of Physiology, volume 510, issue 2, 1998, pages 623–632, ISSN [http://www.worldcat.org/issn/0022-3751 0022-3751], doi [http://dx.doi.org/10.1111/j.1469-7793.1998.623bk.x 10.1111/j.1469-7793.1998.623bk.x]</ref>
<ref name="Eken-1988"> T. Eken, K. Gundersen, Electrical stimulation resembling normal motor-unit activity: effects on denervated fast and slow rat muscles., J Physiol, volume 402, pages 651-69, Aug 1988, PMID [http://www.ncbi.nlm.nih.gov/pubmed/3236252 3236252]</ref>
<ref name="Roy-1999"> RR. Roy, RJ. Talmadge, JA. Hodgson, Y. Oishi, KM. Baldwin, VR. Edgerton, Differential response of fast hindlimb extensor and flexor muscles to exercise in adult spinalized cats., Muscle Nerve, volume 22, issue 2, pages 230-41, Feb 1999, PMID [http://www.ncbi.nlm.nih.gov/pubmed/10024136 10024136]</ref>
<ref name="PetteStaron1997">Dirk Pette, Robert S. Staron, Mammalian Skeletal Muscle Fiber Type Transitions, volume 170, 1997, pages 143–223, ISSN [http://www.worldcat.org/issn/00747696 00747696], doi [http://dx.doi.org/10.1016/S0074-7696(08)61622-8 10.1016/S0074-7696(08)61622-8]</ref>
<ref name="Hämäläinen-1995"> N. Hämäläinen, D. Pette, Patterns of myosin isoforms in mammalian skeletal muscle fibres., Microsc Res Tech, volume 30, issue 5, pages 381-9, Apr 1995, doi [http://dx.doi.org/10.1002/jemt.1070300505 10.1002/jemt.1070300505], PMID [http://www.ncbi.nlm.nih.gov/pubmed/7787237 7787237]</ref>
<ref name="Scott-2001"> W. Scott, J. Stevens, SA. Binder-Macleod, Human skeletal muscle fiber type classifications., Phys Ther, volume 81, issue 11, pages 1810-6, Nov 2001, PMID [http://www.ncbi.nlm.nih.gov/pubmed/11694174 11694174]</ref>
<ref name="Staron-1997"> RS. Staron, Human skeletal muscle fiber types: delineation, development, and distribution., Can J Appl Physiol, volume 22, issue 4, pages 307-27, Aug 1997, PMID [http://www.ncbi.nlm.nih.gov/pubmed/9263616 9263616]</ref>
<ref name="Hilber-1999"> K. Hilber, S. Galler, B. Gohlsch, D. Pette, Kinetic properties of myosin heavy chain isoforms in single fibers from human skeletal muscle., FEBS Lett, volume 455, issue 3, pages 267-70, Jul 1999, PMID [http://www.ncbi.nlm.nih.gov/pubmed/10437786 10437786]</ref>
<ref name="Pette-1999"> D. Pette, H. Peuker, RS. Staron, The impact of biochemical methods for single muscle fibre analysis., Acta Physiol Scand, volume 166, issue 4, pages 261-77, Aug 1999, PMID [http://www.ncbi.nlm.nih.gov/pubmed/10468663 10468663]</ref>
</references>
=Muscle Fiber Types=
Skeletal muscle fibers vary in their characteristics, and there are several different ways of categorizing them. While a simple categorization is appealing, in reality fibers tend to vary in multiple ways, so remember that while this is a useful model, [[All models are wrong]]. This is a little like classifying cars into different types. You can categorize cars based on the number of doors, how fast they are, what shape the back is, etc. The table below shows several classification systems and the characteristics of the fibers<ref name="Scott-2001"/>.
{| class="wikitable"
! colspan="5"|Categorization
! colspan="2"|Characteristics
|-
| '''Contraction speed'''
| '''Myosin ATPase'''
| '''Myosin heavy chain'''
| '''Biochemical'''
| '''Motor Unit Classification'''
| '''Resistance to fatigue'''
| '''Force Generated'''
|-
| Slow Twitch
| Type I
| MHCI
| Slow Twitch Oxidative (SO)
| Slow Twitch Fatigue Resistant
| High
| Low
|-
| rowspan="2"| Fast Twitch
| Type IIa
| MHCIIa
| Fast Twitch Oxidative/Glycolytic (FOG)
| Fast Twitch Fatigue Resistant
| Medium
| Medium
|-
| Type IIb
| MHCIIx/d
| Fast Twitch Glycolytic (FG)
| Fast Twitch Fatigable
| Low
| High
|}
==Notes==
* There is a good correlation between type I and SO fibers, but the correlations between type IIA and FOG and type IIB and FG fibers are not so clear<ref name="Hämäläinen-1995"/>.
* In addition to those shown in the table, mATPase also has IC, IIC, IIAC, IIAB types that are not shown<ref name="Staron-1997"/>.
* The original Myosin heavy chain classification of MHCIIb in humans now appears to be the MHCIIx/MHCIId type found in small mammals<ref name="Hilber-1999"/>, and humans do not actually have the MHCIIb form<ref name="Pette-1999"/>.
[[File:Muscle Fiber Classification.jpg|none|thumb|500px|This is a picture visualizes some of the ways of categorizing muscle fibers.]]
==Fiber Type Plasticity==
There is overwhelming evidence that fibers can change type, with transitions between Type IIa and Type IIb being the most common<ref name="PetteStaron1997"/>. Conversion between Type I and Type II has been shown to occur with severe deconditioning, such as spinal injury<ref name="Roy-1999"/>. The only evidence of transitions from Type II to Type I with training is limited to studies of denervated muscles that were electrically stimulated for weeks<ref name="Eken-1988"/>. In rats, the transformation occurred sequentially as type IIB/IIX to type IIA to type I, with the type IIB/IIX to type IIA occurring after 2 weeks and the type IIA to type I taking longer than 2 months<ref name="WindischGundersen1998"/>.
=Muscle Recruitment=
We control our muscles so that we can lift a heavy weight or gently lift a cup of coffee. Our muscles are made up of many small fibers, and when we use less than our full strength we activate just some of those fibers<ref name="SkeletalMuscle"/>. So lifting the cup of coffee might only use a few of the fibers, but those fibers are fully activated. Each muscle fiber is either generating force or not; there is no in-between. Some muscle fiber types are more easily recruited, and the order is Type I, Type IIa, and finally Type IIb <ref name="MacIntoshGardiner2006"/>.This can be seen in the patterns of [[Glycogen]] depletion. Muscle recruitment has some important implications for training methods. To train all our muscle fibers we either have to generate the maximum force our muscles can produce or we have to exhaust some fibers so that others are activated in their place.
==Endurance Training==
Here's an analogy for muscle recruitment patterns while running long distances. Imagine each muscle fiber is a person and the long run is a war. Initially, the highly trained troops are the first to be deployed. When these highly trained troops become fatigued, then the reserve troops are called in to replace them. Eventually even the reserve troops become fatigued, and the draft calls in anyone who is able bodied. If things go on long enough, then the old men and children have to fight. In the same way we rely on a few well-trained muscle fibers early on in a run. As these muscle fibers become fatigued, we call on less well trained fibers. Thus as the training run progresses we work our way through the various muscle fibers. This is why a 15 mile training run does not provide 75% of the endurance benefit of a 20 mile run.
==Maximum Strength Training==
Lifting heavy weights requires engaging more of the muscle fibers. Maximum strength training has been shown to improve [[Running Economy]] without changing [[VO2max|V̇O<sub>2</sub>max]]<ref name="Støren-2008"/><ref name="Johnson-1997"/><ref name="Millet-2002"/>. Improvements in endurance have also been seen with elite level cyclists undergoing maximum strength training (5-6 reps to failure)<ref name="AagaardAndersen2010"/>.
==Plyometrics==
Plyometrics use explosive exercises where the full strength of the muscles are engaged for a short period of time. Preceded a muscle contraction with muscle extension under load generates maximum muscle engagement. An example of this can be seen in box jumps, where you jump down from a box and then immediately jump back up. The jumping down extends the muscles under load (eccentric exercise) which then helps generate more force on the jump back up. Like Maximum strength training, plyometrics improve [[Running Economy]] and performance without changing [[VO2max|V̇O<sub>2</sub>max]]<ref name="Paavolainen-1999"/><ref name="Turner-2003"/><ref name="SpurrsMurphy2003"/><ref name="Spurs-2002"/>. Plyometrics have also been shown to improve neuromuscular control for running that follows cycling, such as occurs during triathlons<ref name="BonacciGreen2011"/>.
=References=
<references>
<ref name="BonacciGreen2011">Jason Bonacci, Daniel Green, Philo U. Saunders, Melinda Franettovich, Peter Blanch, Bill Vicenzino, Plyometric training as an intervention to correct altered neuromotor control during running after cycling in triathletes: A preliminary randomised controlled trial, Physical Therapy in Sport, volume 12, issue 1, 2011, pages 15–21, ISSN [http://www.worldcat.org/issn/1466853X 1466853X], doi [http://dx.doi.org/10.1016/j.ptsp.2010.10.005 10.1016/j.ptsp.2010.10.005]</ref>
<ref name="Spurs-2002">Plyometric training improves distance running performance: A case study, Journal of Science and Medicine in Sport, volume 5, issue 4, 2002, pages 41, ISSN [http://www.worldcat.org/issn/14402440 14402440], doi [http://dx.doi.org/10.1016/S1440-2440(02)80117-7 10.1016/S1440-2440(02)80117-7]</ref>
<ref name="SpurrsMurphy2003">Robert W. Spurrs, Aron J. Murphy, Mark L. Watsford, The effect of plyometric training on distance running performance, European Journal of Applied Physiology, volume 89, issue 1, 2003, pages 1–7, ISSN [http://www.worldcat.org/issn/1439-6319 1439-6319], doi [http://dx.doi.org/10.1007/s00421-002-0741-y 10.1007/s00421-002-0741-y]</ref>
<ref name="Turner-2003"> AM. Turner, M. Owings, JA. Schwane, Improvement in running economy after 6 weeks of plyometric training., J Strength Cond Res, volume 17, issue 1, pages 60-7, Feb 2003, PMID [http://www.ncbi.nlm.nih.gov/pubmed/12580657 12580657]</ref>
<ref name="AagaardAndersen2010">P. Aagaard, J. L. Andersen, Effects of strength training on endurance capacity in top-level endurance athletes, Scandinavian Journal of Medicine & Science in Sports, volume 20, 2010, pages 39–47, ISSN [http://www.worldcat.org/issn/09057188 09057188], doi [http://dx.doi.org/10.1111/j.1600-0838.2010.01197.x 10.1111/j.1600-0838.2010.01197.x]</ref>
<ref name="Paavolainen-1999"> L. Paavolainen, K. Häkkinen, I. Hämäläinen, A. Nummela, H. Rusko, Explosive-strength training improves 5-km running time by improving running economy and muscle power., J Appl Physiol, volume 86, issue 5, pages 1527-33, May 1999, PMID [http://www.ncbi.nlm.nih.gov/pubmed/10233114 10233114]</ref>
<ref name="Millet-2002"> GP. Millet, B. Jaouen, F. Borrani, R. Candau, Effects of concurrent endurance and strength training on running economy and .VO(2) kinetics., Med Sci Sports Exerc, volume 34, issue 8, pages 1351-9, Aug 2002, PMID [http://www.ncbi.nlm.nih.gov/pubmed/12165692 12165692]</ref>
<ref name="Johnson-1997"> Johnson, Ronald E., et al. "Strength training in female distance runners: impact on running economy." The Journal of Strength & Conditioning Research 11.4 (1997): 224-229.</ref>
<ref name="Støren-2008"> O. Støren, J. Helgerud, EM. Støa, J. Hoff, Maximal strength training improves running economy in distance runners., Med Sci Sports Exerc, volume 40, issue 6, pages 1087-92, Jun 2008, doi [http://dx.doi.org/10.1249/MSS.0b013e318168da2f 10.1249/MSS.0b013e318168da2f], PMID [http://www.ncbi.nlm.nih.gov/pubmed/18460997 18460997]</ref>
<ref name="MacIntoshGardiner2006">Brian R. MacIntosh !!author1!!, Phillip F. Gardiner !!author2!!, Alan J. McComas !!author3!!, Skeletal Muscle: Form And Function, Accessed on 13 April 2013, 2006, publisher Human Kinetics 1, isbn 978-0-7360-4517-9, pages 201–</ref>
<ref name="SkeletalMuscle"> Brian R. MacIntosh, Phillip F. Gardiner, Alan J. McComas, Skeletal muscle : form and functio, date 2006, publisher Human Kinetics, location Champaign, IL, isbn 0736045171</ref>
<ref name="WindischGundersen1998">A. Windisch, K. Gundersen, M. J. Szabolcs, H. Gruber, T. Lomo, Fast to slow transformation of denervated and electrically stimulated rat muscle, The Journal of Physiology, volume 510, issue 2, 1998, pages 623–632, ISSN [http://www.worldcat.org/issn/0022-3751 0022-3751], doi [http://dx.doi.org/10.1111/j.1469-7793.1998.623bk.x 10.1111/j.1469-7793.1998.623bk.x]</ref>
<ref name="Eken-1988"> T. Eken, K. Gundersen, Electrical stimulation resembling normal motor-unit activity: effects on denervated fast and slow rat muscles., J Physiol, volume 402, pages 651-69, Aug 1988, PMID [http://www.ncbi.nlm.nih.gov/pubmed/3236252 3236252]</ref>
<ref name="Roy-1999"> RR. Roy, RJ. Talmadge, JA. Hodgson, Y. Oishi, KM. Baldwin, VR. Edgerton, Differential response of fast hindlimb extensor and flexor muscles to exercise in adult spinalized cats., Muscle Nerve, volume 22, issue 2, pages 230-41, Feb 1999, PMID [http://www.ncbi.nlm.nih.gov/pubmed/10024136 10024136]</ref>
<ref name="PetteStaron1997">Dirk Pette, Robert S. Staron, Mammalian Skeletal Muscle Fiber Type Transitions, volume 170, 1997, pages 143–223, ISSN [http://www.worldcat.org/issn/00747696 00747696], doi [http://dx.doi.org/10.1016/S0074-7696(08)61622-8 10.1016/S0074-7696(08)61622-8]</ref>
<ref name="Hämäläinen-1995"> N. Hämäläinen, D. Pette, Patterns of myosin isoforms in mammalian skeletal muscle fibres., Microsc Res Tech, volume 30, issue 5, pages 381-9, Apr 1995, doi [http://dx.doi.org/10.1002/jemt.1070300505 10.1002/jemt.1070300505], PMID [http://www.ncbi.nlm.nih.gov/pubmed/7787237 7787237]</ref>
<ref name="Scott-2001"> W. Scott, J. Stevens, SA. Binder-Macleod, Human skeletal muscle fiber type classifications., Phys Ther, volume 81, issue 11, pages 1810-6, Nov 2001, PMID [http://www.ncbi.nlm.nih.gov/pubmed/11694174 11694174]</ref>
<ref name="Staron-1997"> RS. Staron, Human skeletal muscle fiber types: delineation, development, and distribution., Can J Appl Physiol, volume 22, issue 4, pages 307-27, Aug 1997, PMID [http://www.ncbi.nlm.nih.gov/pubmed/9263616 9263616]</ref>
<ref name="Hilber-1999"> K. Hilber, S. Galler, B. Gohlsch, D. Pette, Kinetic properties of myosin heavy chain isoforms in single fibers from human skeletal muscle., FEBS Lett, volume 455, issue 3, pages 267-70, Jul 1999, PMID [http://www.ncbi.nlm.nih.gov/pubmed/10437786 10437786]</ref>
<ref name="Pette-1999"> D. Pette, H. Peuker, RS. Staron, The impact of biochemical methods for single muscle fibre analysis., Acta Physiol Scand, volume 166, issue 4, pages 261-77, Aug 1999, PMID [http://www.ncbi.nlm.nih.gov/pubmed/10468663 10468663]</ref>
</references>
