Thread: sprinters fibers
05-09-2005, 09:17 PM #1
What makes a winning sprinter? The answer to this apparently simple question is a complex one including such elements as mental approach, diet and even clothing. But since sprinting performance is heavily dependent on speed of limb movement, one of the biggest single factors contributing to success is physiology(1). The muscle fibres in the winning sprinter's legs are able to contract faster over the short period of the sprint than those of his or her less successful counterparts. Recent research findings have improved our knowledge of how human muscle adapts to training, and the extent to which muscle can alter its ability to meet the fast movement velocities demanded by sprinting performance.
A muscle consists of a bundle of cells known as fibres bound together by envelopes of a connective tissue called collagen. A single fibre comprises a membrane, many nuclei containing genetic information, and thousands of inner strands running the length of the fibre, called myofibrils. Muscle force production is accomplished through the interaction of two protein filaments that make up the myofibril: actin and myosin.
One component of the myosin filament, known as the myosin heavy chain (MHC), determines the functional abilities of the entire muscle fibre. This heavy chain exists in three forms: I, IIa and IIb. Type I fibres contain a predominance of type I MHC and are commonly called slow twitch, while fibre types IIa and IIb contain a predominance of type IIa and IIb MHC respectively, and are known as fast twitch. Slow twitch fibres are so-called because the maximum contraction velocity of a single fibre is approximately one tenth that of a type IIb fibre(2). Type I fibres also produce less maximum force than type IIb fibres(3). Type IIa fibres lie somewhere between type I and type IIb in their maximum contraction velocity and maximum force production.
Because of the high velocity of contraction and the large forces they produce, type IIb fibres are probably one of the key elements required for successful performances in speed-dependent pursuits like sprinting. It is therefore not surprising to find that successful sprint athletes possess more of these IIb fibres than the average person(4). But is this part of a sprinter's make-up pre-determined by genetics? Or can the proportion of type IIb fibres in muscle be increased through training?
Training effects on fibre type
Virtually all the available evidence suggests that the answer to the last question is no. In fact, it has been suggested that type IIb MHC and therefore IIb fibres constitute a 'default' fibre type setting in humans when activity is absent, and evidence of high proportions of this fibre type in paralysed muscle support this theory(5). It has also been known for some time that increases in activities like strength or power training can lead to conversion of muscle fibres. But, unfortunately, this conversion operates in one direction only, changing fast type IIb fibres into slower type IIa fibres(6). Moreover, if heavy loading of muscles continues for a month or more, virtually all type IIb fibres will transform to type IIa, with obvious consequences for sprinting potential(7).
What happens when heavy strength training stops? Do the newly formed type IIa fibres revert back to type IIb? The answer is yes, but recent research has revealed some extraordinary results to which a simple yes does not do justice. Scientists from the Copenhagen Muscle Research Centre examined training and detraining effects on muscle fibre type distribution(8). Biopsies (muscle samples) were taken from the vastus lateralis muscle of nine young sedentary males. All the subjects then undertook three months of heavy resistance training, aimed predominantly at the quadriceps muscle group, which ended with a second muscle biopsy. The subjects then abruptly ceased training and returned to their normal sedentary lifestyles before providing a third biopsy three months later.
05-09-2005, 09:41 PM #2
Good info, cheers.
05-09-2005, 10:57 PM #3Member
- Join Date
- Oct 2004
What does cheers mean? GOod story BTW
05-11-2005, 11:36 PM #4
Cheers is interchangeable with thankyou,
05-12-2005, 11:22 AM #5What happens when heavy strength training stops? Do the newly formed type IIa fibres revert back to type IIb? The answer is yes, but recent research has revealed some extraordinary results to which a simple yes does not do justice. Scientists from the Copenhagen Muscle Research Centre examined training and detraining effects on muscle fibre type distribution(8). Biopsies (muscle samples) were taken from the vastus lateralis muscle of nine young sedentary males. All the subjects then undertook three months of heavy resistance training, aimed predominantly at the quadriceps muscle group, which ended with a second muscle biopsy. The subjects then abruptly ceased training and returned to their normal sedentary lifestyles before providing a third biopsy three months later.
05-14-2005, 01:57 AM #6New Member
- Join Date
- Apr 2005
Sedentary lifestyle results in fibers changing back to IIb. That is to say that contrary to popular belief, sprint training coupled together with weights actualli results in muscle fibers leaning towards type IIa rather than pure fast twitch IIb. In fact they took muscle biopsies of elite sprinters in the 80s and found that some of them even had a slow to fast fiber ratio of 45:55, some even 50:50. Which is to say the CNS plays an even larger role in determining how fast you are rather than simply fiber type. I can't quote from anywhere now and i'm speaking from my own knowledge cos I don't have my sports science journals with me now.
06-08-2005, 11:27 AM #7Junior Member
- Join Date
- May 2005
Sprinting is 90% genetic and 10% mental. Africans have dominated these events because of their light muscle, and the high ratio of FTA and FTB to ST. Thats the genectic part. The mental part is this: The fastest men in the world are "The fastest men in the world" because they cheat. It's time you people accept this. Training has little effect on the ratio of fibers in your muscles! It's not the will to win, but the will to think.
06-08-2005, 01:01 PM #8
Did you read that in a book. Or did you come up with that theory all by yourself?
06-08-2005, 05:31 PM #9
hahaOriginally Posted by Shaka
06-08-2005, 08:57 PM #10Associate Member
Originally Posted by tri-athlete
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- san antonio/houston
06-08-2005, 09:16 PM #11Originally Posted by TestTubeBaby
Originally Posted by keithquig
What I find humorous is his sprinting theory
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