Author Topic: Fiber type is irrelevant for size and strength...but for speed and power...it is  (Read 8447 times)

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Kellyb

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Summary:

1. For size and strength, total muscle fiber cross sectional area is more important than fiber type. With regards to peak force production, the main difference amongst the fibers is their size. Type II's are bigger yet an equal volume of type I's can produce roughly the same peak force. Therefore, for displays of maximum force (strength), or size, fiber type is of little consequence. A good illustration is Lance Armstrong.  He's verified 90% slow twitch, but his legs are possibly bigger than Usain Bolt, who is likely 90% fast twitch.

2.  For displays of rapid tension type II fiber has more importance.

3. If you don't have much FT fiber or much FT cross sectional size, you can strength train for years, get bigger, and the muscle you grow will allow you to increase the relative area of Type II's, allowing you to function more like a naturally FT individual.


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No relationship was observed to exist between muscle strength and muscle fibre composition. Similarly, the muscle strength/cross-sectional area ratio was not related to the proportions of the different fibre types present or to the fraction of the total cross-sectional area occupied by the different fibre types. From the results it can be concluded that there is no difference in the force per unit area which can be generated by the different muscle fibre types present in human skeletal muscle.


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In the women, the relationship between strength and the percentage of type II fibres changed with age (from 16 to 27 years of age) from a positive correlation (only Sargent jump) to negative correlations for all the strength tests, i.e. the more type I fibres the stronger the subject. A positive correlation between strength and the level of physical activity during leisure time was revealed in the women at both ages. The positive correlation between strength and type II fibres in the 16-year-old men had disappeared at age 27.

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The relationship between maximum voluntary concentric strength, muscle fibre type distribution and muscle cross-sectional areas were examined in 23 subjects (7 female and 11 male phys. ed. students as well as 5 male bodybuilders). Maximal knee and elbow extension as well as elbow flexion torque at the angular velocities 30, 90 and 180 degrees per second was measured. Muscle biopsies were taken from vastus lateralis and m. triceps brachii. The muscle cross-sectional area of the thigh and upper arm was measured with computed tomography scanning. The maximal torque correlated strongly to the muscle cross-sectional area times an approximative measure on the lever arm (body height). Maximal tension developed per unit of muscle cross-sectional area did not correlate significantly with per cent type I fibre area and did not differ between the female and male students or bodybuilders.


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Although there was a high correlation between average cross-sectional fiber area and total muscle cross-sectional area within each group, many of the subjects with the largest muscles also tended to have a large number of fibers.

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Muscle biopsy samples were obtained from m. vastus lateralis and m. deltoideus of three high caliber bodybuilders. Tissue specimens were analysed with respect to relative distribution of fast twitch (FT) and slow twitch (ST) fiber types and different indices of fiber area. In comparison to a reference group of competitive power/weight-lifters the following tendencies were observed: the percentage of FT fibers was less, mean fiber area was smaller and selective FT fiber hypertrophy was not evident.

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Subjects with predominantly FT fibers were able to generate 11, 16, 23 and 47 percent greater relative peak torque than could predominantly ST subjects at lever arm velocities of 115, 200, 287 and 400 degrees/second respectively. Likewise the correlation between relative torque production and % FT were significant (p less than .05) and increased from r = 0.44 to r = 0.75 as velocity increased from 115 to 400 degrees/second respectively. These data suggest that muscle fiber composition becomes increasingly more related to power performance as the velocity of movement increases

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Muscle biopsies from m. vastus lateralis of two world class shot putters (shot putter 1 and 2) and the untrained brother of shot putter 1 were analyzed for fiber type distribution with ATPase staining and in situ hybridization for the expression of alkali myosin light chain (MLC) isoforms. Shot putter 2 had a predominance of type II fibers (67 X) and distinct hypertrophy of type I as well as type II fibers (fiber areas of 5939 and 8531 microm2). In shot putter 1, type II fibers amounted to only 40%, due to their selective hypertrophy, however type II fibers (10265 microm2) accounted for 67 2% of the total cross-sectional area. We suggest that the ability to selectively increase the relative area of his type II fibers in the 15 years of strength training was a key element in his success as a shot putter.


« Last Edit: June 08, 2009, 04:34:40 pm by Kellyb »

Kellyb

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The influence of variations in muscle fibre composition on muscle strength and cross-sectional area in untrained males.Maughan RJ, Nimmo MA.

The force produced by a maximum voluntary isometric contraction of the knee-extensor muscles was measured in a group of fifteen healthy young male volunteers. All subjects were untrained at the time of the study. The cross-sectional area of the knee-extensor muscles was measured at the mid-thigh level using computed tomography. Skeletal muscle samples were obtained by needle biopsy from the mid-point of m. vastus lateralis of the stronger leg of each subject. Samples were mounted, frozen and sectioned for histochemical analysis. On the basis of the pH dependent lability of the myosin ATP-ase reaction, fibres were classified as Type I, Type IIA or Type II B. Using computerized planimetry, muscle fibre cross-sectional areas were measured on serial sections stained for succinate dehydrogenase activity. As previously described, muscle strength (maximum voluntary contraction) was correlated with the muscle cross-sectional area (r = 0.70, P less than 0.01). The ratio of strength (in N) to cross-sectional area (in cm2) was 8.92 +/- 1.01 (mean +/- S.D.) with a wide range of values, from 7.09 to 10.85. Muscle fibre composition of m. vastus lateralis in these subjects was 46.1 +/- 10.5% Type I, 42.8 +/- 11.4% Type IIA and 11.1 +/- 9.7% Type IIB. After correction for differences in the cross-sectional areas of the different fibre types, the proportions of total area occupied by the different fibre types were: 43.6 +/- 11.9% Type I, 46.4 +/- 13.1% Type IIA and 10.0 +/- 9.1% Type IIB. No relationship was observed to exist between muscle strength and muscle fibre composition. Similarly, the muscle strength/cross-sectional area ratio was not related to the proportions of the different fibre types present or to the fraction of the total cross-sectional area occupied by the different fibre types. From the results it can be concluded that there is no difference in the force per unit area which can be generated by the different muscle fibre types present in human skeletal muscle. Variations in muscle fibre composition between individuals cannot, therefore, account for the large variations observed in the ratio of strength to muscle cross-sectional area.



Kellyb

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Muscle strength from adolescence to adulthood--relationship to muscle fibre types.Glenmark B, Hedberg G, Kaijser L, Jansson E.
Department of Clinical Physiology, Karolinska Hospital, Stockholm, Sweden.

The aim of the present study was to reinvestigate muscle strength and the relationship to muscle fibre and the level of physical activity in adult men and women previously studied during adolescence. A group of 55 men and 26 women were tested for maximal strength (handgrip, Sargent jump and two-hand lift) and completed a questionnaire concerning physical activity during their leisure time (activity index) at the ages of 16 and 27 years. Biopsy specimens were taken from the vastus lateralis and analysed for fibre type (percentage of I, IIA, IIB) and fibre area (area I, area IIA, area IIB). The sex differences in strength increased from age 16 to 17 years. Body dimension, sex, percentage of type II, mean fibre area and the activity index contributed to explaining 50-75% of the strength at both ages. Different changes in relationship between fibre type composition and strength in women and men was seen with increasing age. In the women, the relationship between strength and the percentage of type II fibres changed with age (from 16 to 27 years of age) from a positive correlation (only Sargent jump) to negative correlations for all the strength tests, i.e. the more type I fibres the stronger the subject. A positive correlation between strength and the level of physical activity during leisure time was revealed in the women at both ages. The positive correlation between strength and type II fibres in the 16-year-old men had disappeared at age 27. No systematic relationships between strength and the level of physical activity were seen in the men at either 16 or 27 years of age. It is suggested that women may be more dependent on physical activity than adult men to develop strength and the percentage of type I fibres reflects the degree of physical activity among adult women but not among adolescent women.


Kellyb

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Kellyb

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Muscle fiber number in biceps brachii in bodybuilders and control subjects.MacDougall JD, Sale DG, Alway SE, Sutton JR.

Muscle fiber numbers were estimated in vivo in biceps brachii in 5 elite male bodybuilders, 7 intermediate caliber bodybuilders, and 13 age-matched controls. Mean fiber area and collagen volume density were calculated from needle biopsies and muscle cross-sectional area by computerized tomographic scanning. Contralateral measurements in a subsample of seven subjects indicated the method for estimation of fiber numbers to have adequate reliability. There was a wide interindividual range for fiber numbers in biceps (172,085-418,884), but despite large differences in muscle size both bodybuilder groups possessed the same number of muscle fibers as the group of untrained controls. Although there was a high correlation between average cross-sectional fiber area and total muscle cross-sectional area within each group, many of the subjects with the largest muscles also tended to have a large number of fibers. Since there were equally well-trained subjects with fewer than normal fiber numbers, we interpret this finding to be due to genetic endowment rather than to training-induced hyperplasia. The proportion of muscle comprised of connective and other noncontractile tissue was the same for all subjects (approximately 13%), thus indicating greater absolute amounts of connective tissue in the trained subjects. We conclude that in humans, heavy resistance training directed toward achieving maximum size in skeletal muscle does not result in an increase in fiber numbers.



Kellyb

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Muscle hypertrophy in bodybuilders.Tesch PA, Larsson L.

Muscle biopsy samples were obtained from m. vastus lateralis and m. deltoideus of three high caliber bodybuilders. Tissue specimens were analysed with respect to relative distribution of fast twitch (FT) and slow twitch (ST) fiber types and different indices of fiber area. In comparison to a reference group of competitive power/weight-lifters the following tendencies were observed: the percentage of FT fibers was less, mean fiber area was smaller and selective FT fiber hypertrophy was not evident. Values for fiber type composition and fiber size were more similar to values reported for physical education students and non-strength trained individuals. The results suggest that weight training induced muscle hypertrophy may be regulated by different mechanisms depending upon the volume and intensity of exercise




Kellyb

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Leg extension power and muscle fiber composition.Coyle EF, Costill DL, Lesmes GR.

The purpose of this investigation was to relate muscle fiber composition to the isokinetic measure of peak torque production through a range of leg extension velocities. Twenty-one males were biopsied from the vastus lateralis muscle to determine their percent distribution of slow twitch (%ST) and fast twitch (%FT) muscle fibers as identified through myofibrillar adenosine triphosphatase activity. All subjects showed a decline in peak torque with increasing velocities. Subjects with predominantly FT fibers were able to generate 11, 16, 23 and 47 percent greater relative peak torque than could predominantly ST subjects at lever arm velocities of 115, 200, 287 and 400 degrees/second respectively. Likewise the correlation between relative torque production and % FT were significant (p less than .05) and increased from r = 0.44 to r = 0.75 as velocity increased from 115 to 400 degrees/second respectively. These data suggest that muscle fiber composition becomes increasingly more related to power performance as the velocity of movement increases.



Kellyb

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adarqui

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nice, I like the shotputter study.. studies like that really hold some weight..

thanks KB, some good stuff in there.



my bad, i was actually doing the TOC for you.. glad i modified it as you were doing it, so it didn't overwrite your post.

1. The influence of variations in muscle fibre composition on muscle strength and cross-sectional area in untrained males.Maughan RJ, Nimmo MA.

Quote
From the results it can be concluded that there is no difference in the force per unit area which can be generated by the different muscle fibre types present in human skeletal muscle. Variations in muscle fibre composition between individuals cannot, therefore, account for the large variations observed in the ratio of strength to muscle cross-sectional area.



2. Muscle strength from adolescence to adulthood--relationship to muscle fibre types.
Glenmark B, Hedberg G, Kaijser L, Jansson E.
Department of Clinical Physiology, Karolinska Hospital, Stockholm, Sweden.


Quote
The sex differences in strength increased from age 16 to 17 years. Body dimension, sex, percentage of type II, mean fibre area and the activity index contributed to explaining 50-75% of the strength at both ages. Different changes in relationship between fibre type composition and strength in women and men was seen with increasing age. In the women, the relationship between strength and the percentage of type II fibres changed with age (from 16 to 27 years of age) from a positive correlation (only Sargent jump) to negative correlations for all the strength tests, i.e. the more type I fibres the stronger the subject.




3.

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The maximal torque correlated strongly to the muscle cross-sectional area times an approximative measure on the lever arm (body height). Maximal tension developed per unit of muscle cross-sectional area did not correlate significantly with per cent type I fibre area and did not differ between the female and male students or bodybuilders. Neither did the relative decrease in torque with increasing contraction velocity show any significant relationship to the per cent type I fibre area.



4. Muscle fiber number in biceps brachii in bodybuilders and control subjects.
MacDougall JD, Sale DG, Alway SE, Sutton JR.


Quote
We conclude that in humans, heavy resistance training directed toward achieving maximum size in skeletal muscle does not result in an increase in fiber numbers.



5. Muscle hypertrophy in bodybuilders.
Tesch PA, Larsson L.


Quote
Values for fiber type composition and fiber size were more similar to values reported for physical education students and non-strength trained individuals. The results suggest that weight training induced muscle hypertrophy may be regulated by different mechanisms depending upon the volume and intensity of exercise



6. Leg extension power and muscle fiber composition.
Coyle EF, Costill DL, Lesmes GR.


Quote
These data suggest that muscle fiber composition becomes increasingly more related to power performance as the velocity of movement increases.


7.

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The large difference between type I and type II fiber size, even in the untrained state, in both shot putter 1 and his brother is not usually seen in humans and maybe a genetic characteristic. We suggest that the ability to selectively increase the relative area of his type II fibers in the 15 years of strength training was a key element in his success as a shot putter. The observed increase in the expression of fast myosin light chain mRNAs in both fiber types is indicative of further adjustment of the myofibrillar apparatus towards the generation of very high peak power.

RJ Nelsen

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Nice, Kelly. Thanks for writing all of that up. Now we just need to compare different types of training and how they affect type II or type I fiber expression.