your welcome
More food for thought:
“A great deal of literature has appeared on the relationship between types of muscle fiber and types of physical activity. Generally, it has been shown that weightlifters, track-and-field athletes and other explosive type athletes tend to have a high percentage of fast twitch muscle fibers in the propulsive muscles, based on studies of characteristic muscle groups such as vastus medialis and gastrocnemius. Conversely, distance runners and other cardiovascular endurance athletes have been shown to have a large percentage of slow twitch fibers in the same muscle groups.
Consequently, it has been deduced that genetics determine what type of athlete one is likely to become. Those accepting that there may also be a training, as well as a genetic determinant of sporting excellence, have concluded that training must be suited precisely to reflect the dominant muscle fiber types of the individual or to attempt to cause adaptive changes in those whose muscle fiber profiles are unsuitable for a given sport.
Thus, we see that Olympic-style weight training is used to stimulate fast twitch fiber changes, if these indeed occur to a significant extent in either the actin-myosin structure or in the enzyme environment of the given muscle fibers.
These deductions and recommendations assume, of course, that histological analysis of muscle correlates accurately with functional muscle performance. In other words, if biochemical and histological tests show that the fibers have a certain color, blood supply, enzyme profile, metabolic structure and so forth, then they must be able to contract, relax or hold a contraction for a certain time and at a certain intensity.
This suggests that all FT fibers (of a given type - FT1 or FT2 fibers etc.) display the same force-time curve and contract rapidly at the same velocity. Similarly, all ST fibers or any other types of fiber class, for that matter, contract at a given rate.
However, scientists know that all structural and functional measurements of events generally display a characteristic bell-shaped (or Gaussian) distribution - and muscle fiber types are no exception. In other words, some FT fibers will be contracting at a very rapid rate, while others will be contracting at a much slower rate. Similarly, some ST fibers will contract at fairly high rates, while others will be thoroughly pedestrian. This leads us to wonder if some FT fibers may be contracting as slowly as the faster contracting ST fibers. If we take into account the findings of some scientists who show that, instead of there being a sequence of a few groups of muscle fiber types, there actually is a smooth continuum of muscle fiber types, constantly in flux at any given instant.
Does this not then suggest that current attempts to classify athletes largely in terms of muscle fiber types and to design training on this basis may be seriously misleading? Are we justified in correlating speed, intensity or fatiguability of muscles solely on the basis of non-functional biochemical/histological tests? Is it accurate to state that a chemically classified muscle sample is indeed functionally very swift, while another is positively geriatric in performance? Attempts to relate muscle fiber typing to certain types of motor ability may be misleading and inaccurate (unless measured by means of the less accurate neurological method of electrostimulation-elicited twitches and EMG assessment of the resulting twitches).
It also has to be pointed out that the expression of muscle speed is not simply one of fiber composition, but also one of anthropometrics. In other words, if one genetically has favorable speed-type leverages for the relevant joint actions, then this will make an enormous difference to performance. If one happens to have a combination of both advantages, then you are much more likely to be a great speed athlete. In addition, research has revealed that elite athletes have an even greater ability for their muscles to relax after contraction, (Note from me: something Charlie has mentioned many times) which suggests that both contraction and relaxation characteristics also have to be examined in understanding the path to excellence in sport.
By the way, studies have shown that the finest marathon runners do not necessarily have the higherst VO2 max, nor do lifters or sprinters with the highest proportion of certain muscle fiber types in certain thigh muscles manage to reach elite levels.
What is interesting about this topic is that no athlete in any sport has ever had extensive muscle biopsies taken from all the major muscles involved in his/her sport to allow us to make any definitive statement about involvement of the whole body in the sport under consideration.
It has also been pointed out that analysis in terms of muscle fiber types can be somewhat imprecise, since it is preferable to refer to motor unit types comprising large groups of muscle fibers of the same type. Research in which the motor nerves from fast and slow motor units have been surgically interchanged in animal studies suggest strongly that the A-alpha motor nerve of a motor unit actually determines the fiber type of the fibers within that motor unit.
Not only do Type 2 motor units differ in many ways from type 1 motor units, but there are also large differences between the motor unit subtypes within type 2. For example, in addition to the familiar metabolic differences, there are also differences in levels of suprspinal excitation required to attain the firing threshold and produce impulse propagation of the motor nerves for the different types of motor unit. Type 2a (fast-oxidative) or type 2b (fast-glycolytic) need more excitation to elicit muscle contraction than do Type 1 (slow) motor units, which is probably the result of differences in nerve fiber diameter and the smaller number of inhibitory synaptic inputs on the Type 1 units.
A large part of the difference in the twitch response may be explained in terms of these differences in excitation levels and in the conduction velocities of the motor nerves (detailed near the end of this essay). This means that neurological factors probably play a more dominant role in determining twitch speed than fiber physiology. The excitation difference also plays a major role in explaining the difference in use, as well as the fiber composition of the muscles. Because slow motor units are more easily recruited and are the most common type of fiber in most muscles, they handle most of the muscular work during our daily activities. Generally, it is only when any physical activity demands greater force, speed or power, that the different fast twitch motor units are recruited.
Though I agree with most of what has been said about the characteristics of the continuum of muscle fiber types and their plasticity in response to mechanical and other stimuli, I am still concerned about possibly unwarranted extrapolations based on a few muscle biopsies from rectus femoris and one or two other leg muscles. In weightlifting and powerlifting, the hamstrings, glutei, calf muscles and erector spinae all play vital roles in lifting from the ground. How can we infer from one or two muscle samples that the part applies to the whole?
By the way, though slow fibers and fast fibers differ regarding the speed of their twitch response, this difference is not as large as some people may believe - it is around 150 milliseconds for type 2b and around 200-230 msec for Type 2a and Type 1, respectively. In other words, the so-called ‘slow’ fibers (or rather endurance fibers) are hardly the geriatric little aerobes which some people think that they are - characteristically, they are only some 35% slower than their faster cousins. Thus, it is not inconceivable that a significant portion of the strength advantage offered by this difference could be offset by favorable joint leverages and different patterns of muscle involvement in a given activity.
Finally, because force production depends not only on excitation of certain motor units, but also on inhibition of the motor units, very aroused mental states or extremely intense training can reduce inhibitory processes to an extent which can produce very large differences in force, power and speed production. The well-known legend of the old grandmother lifting a wrecked car to save her trapped daughter can be explained on this basis, along with the occasional breaking of world records by large margins (e.g. the long lasting long jump of Bob Beamon).
Maybe we also have to be more circumspect in simplistically using terms such as fast and slow fibers and motor units, and focus more on neural factors, inhibitory processes, force-generating qualities and fatigue resistance characteristics in trying to understand prowess in sport.”
Facts and Fallacies of Fitness by Mel C. Siff
Whooh that was long! 
Great post. i have always wondered about the white/red, fast/slow fibers being the dominant force. It also shows about what charlie says about EMS being able to elicit greater changes in muscle power in a way, instead of actually changing the fibre itself, EMS may well create larger or new more powerfull Nerves. Akin to using a12volt battery instead of a 6volt? More electricty getting to the nerves, v’s same nerves and electricty supply but faster acting muscles.
Formula - that would tend to suggest at one point the athlete should spend as much time learning to turn-off neural recrutiment as much as turning on.
other than attempting to keep relaxed, any other ways to Learn to turn-off neural recrutiment? perhaps there could be drills one could perform?
That’s the value of a good therapist - getting tonus just right
no23 - exactly. I attended one of Dr. Siff’s first strength camps and I recall him saying that 1 rep max’s will enhance the ability to relax. He also spent much time on the subject of autogenic training (deep visualization) as a means of establishing better feedforward mechanisms. Finally, he spoke of brain function, specifically the motor cortex and cerebellum and their ability to initiate rapid ballistic movement.
The autogenic training concept has been mentioned by quite a few, but not in practical application, however practiacally - I’ve found is using AIS to be help in this regard.
very good post formula. its interesting that so many in our field are consumed with the development of muscular tension but not the relaxation of muscular tension. for effecient balistic movement to take place the antagonist must relax at the same intensity AND velocity as the agonist contracts.
Somebody review this for me and we’ll see what it tells us !!
Fatigue: Neural and Muscular Mechanisms
(Advances in Experimental Medicine and Biology)
by Patricia A. Pierce, Roger M. Enoka (Editor), Simon C. Gandevia (Editor), Alan J. McComas (Editor), Douglas G. Stuart (Editor), Christine K. Thomas (Editor)
Publisher: Springer; 1 edition (November 30, 1995)
Language: English
ISBN: 0306451395
what kind of injuries can be caused by CNS-fatigue?
i.e.:
…pain in the back, direct at the backbone
…muscle strains
…stuff like knee pain at the patella
and so on. …
We agree to the fact that “CNS-stress” is caused by high int.
But isnt a ham-stream or whatever not also possibly caused by a capacity overloadcapacity overload of the peripheral system?
What is caused by cns-stress practical?
injuries would be a secondary effecy not a primary effect of cns fatigue for example if fatigue is present it is more likly that the imporoper signal or possibly to weak a signal is sent to a muscle and injury results when the body doesn act as it should under healthy condtions. then ofcourse there are the symptoms that come with overtraining.