WHAT IS CNS FATIGUE really?

[lorien]

@duxx

Regarding muscle fyber transition:

“Type IIA possess good aerobic and anaerobic characteristics, whereas type IIB possess good anaerobic characteristics but poor aerobic characteristics.” — p.72

“It now appears that type IIB fibers may in fact be just a pool of unused fibers (with low oxydative ability) that upon recruitment start a shift or transformation ultimately to the type IIA fiber” — p. 72

“Dramatic reduction in the IIB fiber type occur with heavy resistance training, which supports such a theory” — p.72

“Type IIC fibers are very rare in humans and are more oxydative than type IIA and type IIB…” —p. 72

“However, it now appears that the changes occur only within the subtypes of type I or type II fibers…” — p.73 (No shift between type I and type II, only within their subtypes)

“Thus, the old concept of trying to change muscle fiber types appears to be related to changes only within a fiber type” — p.89

“It is not know to what extent muscle fiber remodeling contributes to muscle strenght; however, gradual increase in the number and size of myofibrils and perhaps the fast fiber type conversion of type IIB to type IIA might contribute to force production” — p.89

---

Excerpts from Fleck, Kraemer. Designing Resistance Training Programs. Human Kinetics. 2004.

Give it a few more years of this kind of discussion and we have remodelled the whole human biology ! It’s very interesting, especially for a person like me, who have only rudimentary knowledge of biology and physiology.

The interesting thing, to me at least, is WHY do IIB fibers convert to IIA? If such a questioning (‘why’) even appears meaningful. It could only be a question of physical reactions and not due to a higher systemic reason [sorry duxx; had to tease you a bit ].

I have a vague memory of someone here mentioning (perhaps Charlie) that: when serious muscle atrophy takes place, it’s generally IIA fibers that pass away first, leaving IIB fibers intact to a higher degree. I find this interesting in many ways:

• Are IIB fibers, and their explicit anaerobic qualities, more important for the rudimentary functioning of the human system?
• Would this imply CNS protection (inhibition) kicking in easier when stress to IIB is imposed?
• Would this imply “one of the reasons” why fibers are converted to IIB; when “artificial” stress is imposed (high intensity training) over and over, then the body have to adapt to this situation, and thus must alter the fibers in a way that reduces danger for the integrity of the body’s rudimentary functioning. I.e. by converting fibers to IIA, the body keeps its rudimentary integrity intact (do not mess with IIB)? Reducing the high intensity potential (conversion), but at the same time giving it a chance to progress through different routes (more training, but if so, then with IIA = safer that way)?
• Is this partially why “super compensation” works? When the danger seems to lessen (rest, easier training), a conversion back to IIB might take place?
• Is it only heavy weight training that necessitates conversion, or does this apply to all high volume/high intensity training (where fatigue is reached)?
• Is (CNS) fatigue also a way for the body to win time, to regroup with a better protective tool-set, hence turning performance improvement into just a “positive” side-effect?

Degrees of stress, from less to more (intensity & volume): 1) manageable CNS fatigue (if proper rest cycles); 2) more efficient motor patterns (cutting off the fire from the surrounding); 3) fiber conversion (safer tools); 4) complete CNS shutdown. Reaching 4 would be too late for performance increase, number 3 would be so and so (if longer rest is imposed, and dependent on complexity of the event itself), number 2 would be necessary for any event progression, number 1 just enough for maintaining current condition.

[martn76]

@james_colbert

true but not period. if you train with traditonal means, then yes this holds true becasue the body strives for effecientcy and type 2a are more effecient under such stress, more effeceint than type 2b. but what if we train in a manner that sends nerve signals only at the highest frequency. as i would hope you know high frequency goes hand in hand with type 2b fibers. frequency is everything when it comes to force production. if a high frequency impulse is sent to a slow twitch fiber that fiber will behave like a fast twtich fiber. conversion occurs becasue of condtion. take away the conditions for conversion and no conversion occurs. so if you train under condtions where high frequecny impulses are used therby recruiting type 2b fibers conversion can be avoided. this includes the use of catching falling loads, eliciting the stretch reflex, taking adavatage of the alpha-gamma loop ect. present condtions where type 2b are preferible and they will not convert.

not my athlete, and i believe that many of you are under the impression that maxing all day everyday is all thats going on. benching is simply a tool, max benching is simply a tool. and the majority of his training is plyometric. and explosive. his levels of explosiveness if they are any indicator point to him not having a predominance of slow twtich firbers. i used the term endurance under condtion, the condtion that it is to fast twtich type 2b fiber. it can be done.

explosiveness is simply a matter of rate coding and motor unit recruitment in a timly manner. so benching this often does not have an adverse effect on explosiveness. if anything it reinforces the motor control pattern of high motor unit recruitment high frequency impulse.

sure as hell helped him run faster 4.37 fast. 39 in vert. max bench press completed in 1.09 seconds. sounds explosive to me.

In short, the other elements in his training that is conducive to explosiveness are negating the effects of his bench press training. Without those elements; " …and the majority of his training is plyometric. and explosive. his levels of explosiveness if they are any indicator point to him not having…" Would he be more explosive? What would happen if he trained for more Neuronal Activation as opposed to muscular endurance in the bench? Would it not be more likely that your man wouldbe faster and more explosive?

[martn76]

@lorien

Give it a few more years of this kind of discussion and we have remodelled the whole human biology ! It’s very interesting, especially for a person like me, who have only rudimentary knowledge of biology and physiology.

The interesting thing, to me at least, is WHY do IIB fibers convert to IIA? If such a questioning (‘why’) even appears meaningful. It could only be a question of physical reactions and not due to a higher systemic reason [sorry duxx; had to tease you a bit ].

I have a vague memory of someone here mentioning (perhaps Charlie) that: when serious muscle atrophy takes place, it’s generally IIA fibers that pass away first, leaving IIB fibers intact to a higher degree. I find this interesting in many ways:

• Are IIB fibers, and their explicit anaerobic qualities, more important for the rudimentary functioning of the human system?
• Would this imply CNS protection (inhibition) kicking in easier when stress to IIB is imposed?
• Would this imply “one of the reasons” why fibers are converted to IIB; when “artificial” stress is imposed (high intensity training) over and over, then the body have to adapt to this situation, and thus must alter the fibers in a way that reduces danger for the integrity of the body’s rudimentary functioning. I.e. by converting fibers to IIA, the body keeps its rudimentary integrity intact (do not mess with IIB)? Reducing the high intensity potential (conversion), but at the same time giving it a chance to progress through different routes (more training, but if so, then with IIA = safer that way)?
• Is this partially why “super compensation” works? When the danger seems to lessen (rest, easier training), a conversion back to IIB might take place?
• Is it only heavy weight training that necessitates conversion, or does this apply to all high volume/high intensity training (where fatigue is reached)?
• Is (CNS) fatigue also a way for the body to win time, to regroup with a better protective tool-set, hence turning performance improvement into just a “positive” side-effect?

Degrees of stress, from less to more (intensity & volume): 1) manageable CNS fatigue (if proper rest cycles); 2) more efficient motor patterns (cutting off the fire from the surrounding); 3) fiber conversion (safer tools); 4) complete CNS shutdown. Reaching 4 would be too late for performance increase, number 3 would be so and so (if longer rest is imposed, and dependent on complexity of the event itself), number 2 would be necessary for any event progression, number 1 just enough for maintaining current condition.

The fast twitch fiber sub-conversions are a matter of thermodynamics (conversion of energy from one form into another) . More efficiency in brief, the body knows that it can cleave more energy from adapting fiber to utilise immediate, (myglobin), alactic (phosphates) lactic (glycolysis) and Aerobic (Oxidative, pyruvic, fats). In short Type IIA are capable of utilising ALL the energy systems of the body so it can produce more work for a given amount of heat lost. The disadvantage of being all things to all men is the blunting of the rate at which substrates are broken on the glycolytic side and the twitch speed and force production. The solution is to training as explosively as possible but to avoid spurious work and intermediate intensities; and to do just enough low intensity elements.

More efficiency equals less speed and power for muscle. Please do not confuse this with efficiency of sprinting actions. I agree.

[Charlie_Francis]

A terrific discussion! The conversion back and forth appears clear and the advantages of selection of work and the timing of such work (effect of taper and recovery especially) are being brought into sharper focus.

[james_colbert]

@martn76

In short, the other elements in his training that is conducive to explosiveness are negating the effects of his bench press training. Without those elements; " …and the majority of his training is plyometric. and explosive. his levels of explosiveness if they are any indicator point to him not having…" Would he be more explosive? What would happen if he trained for more Neuronal Activation as opposed to muscular endurance in the bench? Would it not be more likely that your man wouldbe faster and more explosive?

your not getting it its not muscular endurance in the sense of how you use the phrase.

[Charlie_Francis]

Think also in terms of timing. The plasticity of fibre is influenced by the duration over which a shift is made. Demand during heavy training will eventually move towards IIa, but bursts of extreme intensity, as long as the capacity to generate this remains intact, facilitated by 3/1 or even 2/1 intensification schemes, will slow the shift, and a reduction of overall workload combined with active rest will shift back towards IIb in the taper. The effectiveness of the shift back to IIb is proportionate to the time spent shifting towards IIa, supporting the concept of triple periodization in the short sprints.
Any way you look at it, this validates the high/low concept, as medium intensity work when added to high intensity work will hasten conversion to IIa and be detremental to ultimate performance.

[Stevemac24]

Following a prolonged period of training MHC becomes stable. Also research has found that over high intensity training periods that decreases in speed and power related variables are unrelated to changes in MHC expression.

[martn76]

@Charlie_Francis

Think also in terms of timing. The plasticity of fibre is influenced by the duration over which a shift is made. Demand during heavy training will eventually move towards IIa, but bursts of extreme intensity, as long as the capacity to generate this remains intact, facilitated by 3/1 or even 2/1 intensification schemes, will slow the shift, and a reduction of overall workload combined with active rest will shift back towards IIb in the taper. The effectiveness of the shift back to IIb is proportionate to the time spent shifting towards IIa, supporting the concept of triple periodization in the short sprints.
Any way you look at it, this validates the high/low concept, as medium intensity work when added to high intensity work will hasten conversion to IIa and be detremental to ultimate performance.

Exactly. Thats one thing that must be taken into consideration. If it took 3 weeks for conversions to occur then it takes 3 weeks for the return of the original fiber composition. Whats even more exciting is the fact that some type IIB overshoot occurs where there is more than before the commencement of the conversion re-conversion within the fast fiber sub-group.

[martn76]

@james_colbert

your not getting it its not muscular endurance in the sense of how you use the phrase.

But it is because of the density of the session (work/rest ratio). What else can it be may I clarify that I mean strength endurance.

[martn76]

@Stevemac24

Following a prolonged period of training MHC becomes stable. Also research has found that over high intensity training periods that decreases in speed and power related variables are unrelated to changes in MHC expression.

Power and speed are affected. Hence the beneficial effect when load is decreased for taper. The MHC becomes stable to the detriment of type IIA and IIB and in favour of type IIC. Bodybuilders are a perfect example. They undertake continuos heavy resistance training mostly with very little in the changing of load or intensity. Hence when tested for generation of power. They fall way behind AT EVERY LOAD in comparison to discus and shot put throwers. In fact their ability to generate power and speed is limited both in peak and average power in the bench press. Biopsy readings (though not accurate) confirm this.

This can be explained by their lack of high rate fast fibers and greater endurance strength (type IIC) characteristics. A relativley long period of rest/unloading would recover and overshoot the fiber make-up. Leading to increases in power and speed.

MHC stability is not wanted if it does not lead to improvements in performance. MHC conversions are different in individuals. Some people are lucky, they have bi-directionality in the MHC expression as opposed to uni-directionality, where training leads only to muscle becoming more endurance/efficiency based. One thing is certain control of training loads and appropriate training followed by de-loading leads to re-conversion from slower isoforms to faster ones and if you do it right you even get an overshoot!!! Wonderful.

These findings have been verified by IAAF backed research (NSA). Check out (I always quote this researcher because his research is specific to athletes) Gunter Tidow. I am sure that if
you do a search for Tidow on this site you will find the relevant info. Bosco and Prof Dusan Hamar (Fitrodyne) have confirmed this. Loading and unloading can not be underestimated for its effects on the plasticity of muscle. In fact Bosco was sooo spooked by his findings that he recommended that heavy strength training be done for limited periods of time by Italian athletes hence the poultry 4-6 week cycle done by Minnea at the beginning of a training cycle. We do not have to take drastic stances with this info but it means that we have to really think about fatigue and potentiation. In fact think about it, if you leave your athlete in a continuously fatigued state then muscle will take on the characteristics of slower fiber/isoforms. When rested the muscle does not have to rely on other energy substrates and so is more likely to become more SPECIALISED for speed, strength and power.

[Stevemac24]

@martn76

Power and speed are affected. Hence the beneficial effect when load is decreased for taper.

Powerman wrote sometime ago that neural activity is and always will be the defining factor. It just doesn’t appear to be that important once neural and endocrine factors are considered.

@martn76

The MHC becomes stable to the detriment of type IIA and IIB and in favour of type IIC. Bodybuilders are a perfect example. They undertake continuos heavy resistance training mostly with very little in the changing of load or intensity. Hence when tested for generation of power. They fall way behind AT EVERY LOAD in comparison to discus and shot put throwers. In fact their ability to generate power and speed is limited both in peak and average power in the bench press. Biopsy readings (though not accurate) confirm this.

This can be explained by their lack of high rate fast fibers and greater endurance strength (type IIC) characteristics. A relativley long period of rest/unloading would recover and overshoot the fiber make-up. Leading to increases in power and speed.

@martn76

MHC stability is not wanted if it does not lead to improvements in performance. MHC conversions are different in individuals. Some people are lucky, they have bi-directionality in the MHC expression as opposed to uni-directionality, where training leads only to muscle becoming more endurance/efficiency based. One thing is certain control of training loads and appropriate training followed by de-loading leads to re-conversion from slower isoforms to faster ones and if you do it right you even get an overshoot!!! Wonderful.

That is a huge extrapolation from the literature. In CFTS there is always waves of strength and / or power work both of which cause conversions IIB>>IIA. "Detraining,” means doing no training from the original research, which you are referring. 10 days tapering of reduced training load/intensity won’t permit an overshoot as your suggesting. As stated research has shown as well that the shift in MHC expression does not correlate to performance.

Expression of MHC-IIx is more akin to a symptom of unloading, rather than an actual causal factor in recovery.

Chiu also stated RFD is not highly related to relative expression of MHC IIb and, therefore, may not be concomitantly altered with reduced percentage of MHC IIb in the early stages of training.

@martn76

These findings have been verified by IAAF backed research (NSA). Check out (I always quote this researcher because his research is specific to athletes) Gunter Tidow. I am sure that if
you do a search for Tidow on this site you will find the relevant info. Bosco and Prof Dusan Hamar (Fitrodyne) have confirmed this. Loading and unloading can not be underestimated for its effects on the plasticity of muscle. In fact Bosco was sooo spooked by his findings that he recommended that heavy strength training be done for limited periods of time by Italian athletes hence the poultry 4-6 week cycle done by Minnea and Donati at the beginning of a training cycle. We do not have to take drastic stances with this info but it means that we have to really think about fatigue and potentiation. In fact think about it, if you leave your athlete in a continuously fatigued state then muscle will take on the characteristics of slower fiber/isoforms. When rested the muscle does not have to rely on other energy substrates and so is more likely to become more SPECIALISED for speed, strength and power.

Not doubting the importance of loading and unloading but I think the key benefits is related to the neuroendorcrine system. Yes fibre coversion may play a role but not as you are suggesting.

[Charlie_Francis]

@martn76

Exactly. Thats one thing that must be taken into consideration. If it took 3 weeks for conversions to occur then it takes 3 weeks for the return of the original fiber composition. Whats even more exciting is the fact that some type IIB overshoot occurs where there is more than before the commencement of the conversion re-conversion within the fast fiber sub-group.

I would not suggest that conversion times have to be the same. You can delay the conversion, as I have described, from IIb to IIa, but allow the switch from IIa to IIb to proceed normally at the end. Overshoot is most likely in a final taper where the rest ratio is greatest.

[Charlie_Francis]

@Stevemac24

Powerman wrote sometime ago that neural activity is and always will be the defining factor. It just doesn’t appear to be that important once neural and endocrine factors are considered.

That is a huge extrapolation from the literature. In CFTS there is always waves of strength and / or power work both of which cause conversions IIB>>IIA. "Detraining,” means doing no training from the original research, which you are referring. 10 days tapering of reduced training load/intensity won’t permit an overshoot as your suggesting. As stated research has shown as well that the shift in MHC expression does not correlate to performance.

Expression of MHC-IIx is more akin to a symptom of unloading, rather than an actual causal factor in recovery.

Chiu also stated RFD is not highly related to relative expression of MHC IIb and, therefore, may not be concomitantly altered with reduced percentage of MHC IIb in the early stages of training.

Not doubting the importance of loading and unloading but I think the key benefits is related to the neuroendorcrine system. Yes fibre coversion may play a role but not as you are suggesting.

While the neuroendocrine factor is of critical importance, what are the factors that trigger beneficial changes? While changes in the neuroendocrine system, and the fibre, and loading and unloading are occuring in lock step, how are they not interrelated/interdependent?

[Stevemac24]

@Charlie_Francis

While the neuroendocrine factor is of critical importance, what are the factors that trigger beneficial changes? While changes in the neuroendocrine system, and the fibre, and loading and unloading are occuring in lock step, how are they not interrelated/interdependent?

Optimal nutrition and supplementation, proper selection and management of workloads (including competitions), restoration methods etc.

They are interrelated just as factors concerning the CNS are – but I wouldn’t place all my chickens in one basket (MHC). CNS-performance would be the area of more so concern? High intensity training periods that decreases in speed and power related variables are unrelated to changes in MHC expression.

[Charlie_Francis]

@Stevemac24

Optimal nutrition and supplementation, proper selection and management of workloads (including competitions), restoration methods etc.

They are interrelated just as factors concerning the CNS are – but I wouldn’t place all my chickens in one basket (MHC). CNS-performance would be the area of more so concern? High intensity training periods that decreases in speed and power related variables are unrelated to changes in MHC expression.

Let’s put it this way. Effective training, supplementation, therapy, and recovery are the priorities and how they all affect performance can be debated at liesure.

[james_colbert]

@martn76

But it is because of the density of the session (work/rest ratio). What else can it be may I clarify that I mean strength endurance.

in that respect you are correct. but this is to simple to understand the efect on the system. endurance as you state it would suggest that training is submaximal and therefor does not add to explosive power. at its most simpliest what is it that we are after? high motor unit recruitment high frequency rate coding. velocity of contraction is everything in training if this is high the resultant effect is explosive (now it gets a bit more complex than that but for simplicity sake we will use this explanation) if you achieve these standards repeatedly in training then power output is not being limited it s neuroal components are being trained. just like motor patterns are learned and reinforced, explosivnes is learned and reinforced. everything is neurological if the signal is explosive then it can be done over and over again. ofcourse this has to be trained.

[james_colbert]

“muscle genes are regulated largely by mechanical stimulation.”

“weightlifters have a considerably higher proportion of FT fibers, a fact which cannot be explained by the contention that specific genetic types escel at specific sports. Bodybuilders have about 10% fewer FT fibers (or 10% more ST fibers) than untrained subjects, while weightlifters have about 10% more FT fibers.”

siff. supertraining.

we can see here that “weightlifting” (lifting loads without consideration to velocity rate of force production etc.) in general is not the cause of fiber type conversion but rather how weight is lifted which causes fiber chage. the idea that training to a certain level and then ceasing or tapering training to achieve a switch back to the preferable fast-twtich isoform is invalid since conversion of fiber types from type 1 or type 2a to type 2b occur only under condtions of extreme immobilisation. but this doesnt matter becasue the answer to negating adverse fiber conversion is to train in a manner which recruits type 2b fibers and thereby mechanically stimulating the proper isoform for further proliforation of fast twtich fiber.

[svass]

@james_colbert

we can see here that “weightlifting” (lifting loads without consideration to velocity rate of force production etc.) in general is not the cause of fiber type conversion but rather how weight is lifted which causes fiber chage. the idea that training to a certain level and then ceasing or tapering training to achieve a switch back to the preferable fast-twtich isoform is invalid since conversion of fiber types from type 1 or type 2a to type 2b occur only under condtions of extreme immobilisation. but this doesnt matter becasue the answer to negating adverse fiber conversion is to train in a manner which recruits type 2b fibers and thereby mechanically stimulating the proper isoform for further proliforation of fast twtich fiber.

From Kramer (2003) - Muscle Fiber Characteristics and Performance Correlates of Male Olympic-Style Weightlifters:

“The weightlifters in this investigation exhibited performance characteristics typical of national-level athletes as indicated by the 1 repetition maximum (1RM) for the snatch and the clean and jerk (17, 31). Of particular importance to this investigation are the results of the muscle biopsies. Previous data on muscle fiber characteristics of weightlifters have either grouped these athletes with athletes from other strength sports (39, 46, 48), or have only reported percentages of the FT and ST populations of fibers (20, 39, 46, 47), and may have missed potentially subtle differences between these populations”

“The percentage of fiber types observed for the WL in the present study are similar to what has been previously reported for other resistance-trained athletes (20, 31, 39, 46–48), including powerlifters (15). The large percentage of IIA fibers in the vastus lateralis m. is also similar to what has been reported for other types of strength training (1, 24, 42, 44); sprint training (28); and endurance-type activities (18, 29). Additionally, a large percentage of IIA fibers has also been reported for other resistance-trained muscles (3, 30, 32, 46). Such large percentages of type IIA fibers are apparent in both strength/power athletes and endurance athletes and appear to be a natural adaptation to the recruitment of the high threshold motor units comprising the type IIB population, ultimately causing an apparent IIB to IIA transformation. Therefore, differences in the performance capabilities for those training for high muscular power or force (i.e., weightlifters and powerlifters) vs. those training for aerobic endurance appear to be due to factors other than mATPase percent fiber-type composition.”

"Compared with previous reports on powerlifters, the area for the WL were slightly greater for IIA fibers and less for I fibers (15). The greater area for IIA fibers for the WL may be due to the greater power requirements for WL when compared with powerlifting; thus this combination of fiber type and area may be an important factor in weightlifting performance. Although it is known that IIB fibers exhibit faster in vitro contractile velocities than IIA fibers (49), the IIA fibers make up a disproportionally greater area in the WL, which positively influences force production. Since power is the product of force and velocity, the increased force capability apparently outweighs any possible effects on velocity, thus enhancing power. It should also be noted that it is likely that the contractile velocities of either types IIA or IIB fibers are more than adequate for the velocity requirements of the sport of weightlifting"

"Cross-sectional studies on the chronic effects of resistance exercise with elite athletes compared with untrained controls have reported greater percentages of type IIA fibers and little or no presence of IIB fibers (15, 30, 31, 39, 46), whereas the percentage of type I fibers have been quite variable. It should be noted that successful WL and powerlifters both exhibit 46–48% type I fibers, which is not unlike untrained controls (15). As such, it appears that the percent type I fibers is not as critical a variable for the subjects studied as is the percent type IIA fibers and the percent area IIA. Although it has been suggested that IIB fibers may be important for elite sprinters (6), such a fiber profile was not evident in this weightlifting population."

“MHC isoform content contributes greatly to the contractile force and velocity of a muscle fiber (43) and is highly related to the mATPase fiber-type profile in humans (13). MHC expression has been shown to readily adapt to a resistance exercise stimulus (1, 13, 24, 44) and is most likely an important factor for enhanced muscular strength and power. It should be noted here that the percent MHC expression is closely associated with the percent fiber type area (13), and most likely represents an important contractile variable for the WL. As shown in Table 3 , the WL exhibited a considerably greater percent fiber type area for type IIA fibers when compared with the CON group. The WL exhibited an almost complete lack of MHC IIb and a large percentage of type MHC IIa. Such results closely agree with the fiber type area data (see Table 3 ), as has been previously reported (13). It appears that IIB fibers and MHC IIb are not essential for elite weightlifting capabilities. Compared with highly trained powerlifters, the WL exhibit slightly greater MHC IIa and less MHC IIb (15). Although some previous reports have suggested strength training results in an increase in MHC IIb expression (4), or that sprint training induces an MHC I to MHC IIa transition (5), the results of the present study do not support such patterns. Recent data from swimmers has suggested that a precompetition training taper may result in increased expression of fast isoforms of myosin light chains (49). Data from the present study on weightlifters does not indicate appreciable expression of fast protein isoforms (i.e., 1.4% MHC IIb), but further research is necessary to determine expression of other contractile regulatory proteins and their adaptations to training.”

“Practical Applications - The muscle characteristics contributing most to weightlifting performances appear to be the percent IIA fibers and the percent area of IIA fibers. Two points should be made here: (1) type IIB fibers were practically nonexistent in the WL, and (2) the percentage of type I fibers were not significantly different from the CON subjects. This indicates that for the weightlifters used in the present study, the percent of fibers (i.e., type I vs. type II) is not as critical as the percent fiber type area (i.e., percent area type I vs. percent area type IIA vs. percent area type IIB). Rather than possessing a low percentage of type I fibers and a high percentage of type II fibers, successful weightlifting performances are dependent on possessing a high percentage of type IIA fibers and a low percentage of type IIB fibers. Capillary densities of the WL was lower compared with the CON and appeared to be due to a lower density for the fibers most critical for weightlifting performance, the IIA fibers. On the other hand, it should be noted that the number of capillaries for each fiber was preserved. Preliminary data on female weightlifters suggests they exhibit similar fiber characteristics to those of the men reported in the present study (unpublished data), but further research is needed to clarify these comparisons. Weightlifting performance was correlated to characteristics of the type II fiber population, whereas vertical jump power holds promise as a potential field test for fiber characteristics. Collectively, these data will provide comparative information when studying other forms of resistance exercise and high-power activities.”

Comments from anyone?

[james_colbert]

@svass

From Kramer (2003) - Muscle Fiber Characteristics and Performance Correlates of Male Olympic-Style Weightlifters:

“The weightlifters in this investigation exhibited performance characteristics typical of national-level athletes as indicated by the 1 repetition maximum (1RM) for the snatch and the clean and jerk (17, 31). Of particular importance to this investigation are the results of the muscle biopsies. Previous data on muscle fiber characteristics of weightlifters have either grouped these athletes with athletes from other strength sports (39, 46, 48), or have only reported percentages of the FT and ST populations of fibers (20, 39, 46, 47), and may have missed potentially subtle differences between these populations”

“The percentage of fiber types observed for the WL in the present study are similar to what has been previously reported for other resistance-trained athletes (20, 31, 39, 46–48), including powerlifters (15). The large percentage of IIA fibers in the vastus lateralis m. is also similar to what has been reported for other types of strength training (1, 24, 42, 44); sprint training (28); and endurance-type activities (18, 29). Additionally, a large percentage of IIA fibers has also been reported for other resistance-trained muscles (3, 30, 32, 46). Such large percentages of type IIA fibers are apparent in both strength/power athletes and endurance athletes and appear to be a natural adaptation to the recruitment of the high threshold motor units comprising the type IIB population, ultimately causing an apparent IIB to IIA transformation. Therefore, differences in the performance capabilities for those training for high muscular power or force (i.e., weightlifters and powerlifters) vs. those training for aerobic endurance appear to be due to factors other than mATPase percent fiber-type composition.”

"Compared with previous reports on powerlifters, the area for the WL were slightly greater for IIA fibers and less for I fibers (15). The greater area for IIA fibers for the WL may be due to the greater power requirements for WL when compared with powerlifting; thus this combination of fiber type and area may be an important factor in weightlifting performance. Although it is known that IIB fibers exhibit faster in vitro contractile velocities than IIA fibers (49), the IIA fibers make up a disproportionally greater area in the WL, which positively influences force production. Since power is the product of force and velocity, the increased force capability apparently outweighs any possible effects on velocity, thus enhancing power. It should also be noted that it is likely that the contractile velocities of either types IIA or IIB fibers are more than adequate for the velocity requirements of the sport of weightlifting"

"Cross-sectional studies on the chronic effects of resistance exercise with elite athletes compared with untrained controls have reported greater percentages of type IIA fibers and little or no presence of IIB fibers (15, 30, 31, 39, 46), whereas the percentage of type I fibers have been quite variable. It should be noted that successful WL and powerlifters both exhibit 46–48% type I fibers, which is not unlike untrained controls (15). As such, it appears that the percent type I fibers is not as critical a variable for the subjects studied as is the percent type IIA fibers and the percent area IIA. Although it has been suggested that IIB fibers may be important for elite sprinters (6), such a fiber profile was not evident in this weightlifting population."

“MHC isoform content contributes greatly to the contractile force and velocity of a muscle fiber (43) and is highly related to the mATPase fiber-type profile in humans (13). MHC expression has been shown to readily adapt to a resistance exercise stimulus (1, 13, 24, 44) and is most likely an important factor for enhanced muscular strength and power. It should be noted here that the percent MHC expression is closely associated with the percent fiber type area (13), and most likely represents an important contractile variable for the WL. As shown in Table 3 , the WL exhibited a considerably greater percent fiber type area for type IIA fibers when compared with the CON group. The WL exhibited an almost complete lack of MHC IIb and a large percentage of type MHC IIa. Such results closely agree with the fiber type area data (see Table 3 ), as has been previously reported (13). It appears that IIB fibers and MHC IIb are not essential for elite weightlifting capabilities. Compared with highly trained powerlifters, the WL exhibit slightly greater MHC IIa and less MHC IIb (15). Although some previous reports have suggested strength training results in an increase in MHC IIb expression (4), or that sprint training induces an MHC I to MHC IIa transition (5), the results of the present study do not support such patterns. Recent data from swimmers has suggested that a precompetition training taper may result in increased expression of fast isoforms of myosin light chains (49). Data from the present study on weightlifters does not indicate appreciable expression of fast protein isoforms (i.e., 1.4% MHC IIb), but further research is necessary to determine expression of other contractile regulatory proteins and their adaptations to training.”

“Practical Applications - The muscle characteristics contributing most to weightlifting performances appear to be the percent IIA fibers and the percent area of IIA fibers. Two points should be made here: (1) type IIB fibers were practically nonexistent in the WL, and (2) the percentage of type I fibers were not significantly different from the CON subjects. This indicates that for the weightlifters used in the present study, the percent of fibers (i.e., type I vs. type II) is not as critical as the percent fiber type area (i.e., percent area type I vs. percent area type IIA vs. percent area type IIB). Rather than possessing a low percentage of type I fibers and a high percentage of type II fibers, successful weightlifting performances are dependent on possessing a high percentage of type IIA fibers and a low percentage of type IIB fibers. Capillary densities of the WL was lower compared with the CON and appeared to be due to a lower density for the fibers most critical for weightlifting performance, the IIA fibers. On the other hand, it should be noted that the number of capillaries for each fiber was preserved. Preliminary data on female weightlifters suggests they exhibit similar fiber characteristics to those of the men reported in the present study (unpublished data), but further research is needed to clarify these comparisons. Weightlifting performance was correlated to characteristics of the type II fiber population, whereas vertical jump power holds promise as a potential field test for fiber characteristics. Collectively, these data will provide comparative information when studying other forms of resistance exercise and high-power activities.”

Comments from anyone?

conflicting studies… dont u hate when that happens. but the objective was not to state that we should train like weightlifters rather that the isoform displayed is closely related to mechanical stimulation. in your study it said that type 2b may be important for sprinters. if that is so then we should look at what occurs during sprinting and build a strenght training program to relfect those needs.

[Charlie_Francis]

@james_colbert

conflicting studies… dont u hate when that happens. but the objective was not to state that we should train like weightlifters rather that the isoform displayed is closely related to mechanical stimulation. in your study it said that type 2b may be important for sprinters. if that is so then we should look at what occurs during sprinting and build a strenght training program to relfect those needs.

Yes. that makes sense