rol van zenuwstelsel in krachtleverantie

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Erg interessant, met name de uitleg mbt het principe van specifiteit van training.



How to improve your performance by optimizing the functioning of your nervous system

When a muscle becomes stronger in response to training, the gain in strength is usually attributed to an improvement in the size or quality of the muscle. The truth, however, is that strength upgrades can occur without any change in the muscle at all. Many upswings in strength are actually the result of alterations in the way the muscle is controlled by the NERVOUS SYSTEM.



Specifically, the nervous system can do a better job of recruiting muscle fibres and collections of muscle cells (motor units) within the muscle during an athlete's sporting activity, thus producing more forceful movements. The nervous system might also become more accomplished at stimulating 'synergists', i. e., muscles which aid the primary muscle in carrying out its assigned function. Importantly, the nervous system can also enhance its ability to inhibit 'antagonists', i. e., muscles which produce forces counter to the desired direction of movement; when this 'restraining order' is put in place, prime movers and synergists can create considerably stronger movements.
However, bear in mind that those three key roles - activating, synergizing, and inhibiting - only scratch the surface of what the nervous system can do to improve strength. From a neural standpoint, strength is a function not only of how well the nervous system stimulates prime movers and synergists and inhibits antagonists - but of HOW LONG the nervous system chooses to sustain this stimulation and inhibition. Brief stimulations lasting no more than a few milliseconds tend to produce modest movements, but a more continuous activation/inhibition of key muscles allows forces to be maintained for a longer period of time, thus permitting the muscles to carry out more total work.
Energy-efficient as well
And don't forget that the nervous system may also become more highly reactive - and thus able to stimulate motor units more quickly. While this by itself does not upgrade force production, it allows forces to develop more rapidly, i. e., it converts strength into power. To put it another way, if you are a strong Tour de France cyclist and your nerves learn to activate your leg muscles more quickly, you would have not only the strength to scale the various mountains along the Tour's route but also the power to climb those promontories quickly. If you are a competitive runner (or at least you run during your sporting activity), you would be able to move along at higher rates of speed.
Finally, the nervous system can also learn to activate motor units in a way which will produce not only the desired level of strength and power for a particular sport but also the most energy-efficient production of strength and power. By 'dialling up' just the right motor units for a particular activity and 'calling' them at the correct time, the nervous system enhances coordination (skill and efficiency of movement), thus conserving energy and allowing competitive levels of effort to be carried out at a lower (and thus easier) percentage of 'max'. It matters not whether the 'max' refers to maximal aerobic capacity (VO2max), maximal running speed, max cycling speed, max rowing speed, top swimming (http://www.pponline.co.uk/encyc/swimming.htm) speed, etc. - if the nervous system allows any effort to be carried out at a lower percentage of maximal, that effort will be easier to tolerate and sustain during workouts and competitions. All of these positive changes within the nervous system (spiked stimulation, synergy, inhibition, continuity, reactivity, and efficiency) can be called 'neural adaptations' to training. As you can see, proper nervous-system activity is critically important for athletic success. The million-pound question is: how should you structure your training programme in order to optimize the functioning of your nervous system?
A hint from science
Fortunately, scientific research provides a number of important clues. For example, in a key study carried out more than two decades ago, researchers simply trained the elbow-flexor muscles of their subjects (basically, the biceps brachii, brachialis, and brachioradialis muscles). An important aspect of this research was that each athlete strength-trained only one arm, with the other arm serving as a 'control'. At the end of the study, elbow-flexor strength in the athletes' trained arms had improved by about 35 per cent ('Neural Factors vs. Hypertrophy in Time Course of Muscle Strength Gain,' Am. J. Phys. Med. Rehabil., vol. 58, pp. 115-130, 1979).
As part of their research, the exercise scientists involved in this investigation placed electrodes on the athletes' arms directly over their elbow-flexor muscles, both at the beginning and end of the study. During elbow flexion, these electrodes detected and recorded electrical activity in the elbow flexors; each recording was quantified as an 'integrated electromyogram', or I EMG. By creating an I EMG before and after the training period, the scientists could uncover changes in the way the athletes' nervous systems were regulating the elbow flexors in response to the training. As you might expect, the I EMG for a particular muscle tends to increase in response to appropriate strength training, and enhancements in I EMG are correlated with improvements in voluntary strength. A more expansive I EMG can mean that the nervous system is recruiting more muscle cells to carry out a specific activity.
Interestingly enough, in this benchmark study the cross-sectional areas of the trained arms increased over the course of the investigation by almost 10 per cent, indicating that some of the observed gains in strength were due to increased muscle volume. To put it simply, individual muscle cells within the elbow flexors got bigger, and as they grew in size they were able to create more force.
However, a significant portion of the strength gain was caused by neural adaptation. Activation level (I EMG) increased by more than 10 per cent over the course of the study, indicating that the nervous system was doing a better job of recruiting the muscle fibres required for forceful elbow flexion.

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Stronger fibres means fewer are needed
But here's where things got really interesting: in the trained arm, the activation level (I EMG) linked with a particular quantity of force DECLINED, and the amount of force associated with a particular activation level (I EMG) INCREASED significantly. In other words, after training it took less nervous-system activity to create a specific force (since the individual muscle fibres were stronger, fewer needed to be recruited to generate a fixed amount of force), but for a given activation level (I EMG), greater force was automatically generated (since the nervous system was recruiting stronger individual muscle cells).
As you might expect, it is possible to tease apart the changes in strength associated with differences in (1) activation level and (2) muscle size merely by plotting I EMG against force during the muscle activity of interest - before and after training. To understand how this is possible, you need to know that the relationship between force and I EMG tends to be linear, i. e., as force increases I EMG also expands in a straightforward and linear manner. However, as muscle size increases the slope of this line will be less steep, i. e., augmentations in I EMG will be smaller for each unit increase in force, since the new bulkiness of the muscle fibres means that the nervous system has to dial up fewer fibres to create a given level of strength. To put it another way, the (bigger) muscle is making it easier for the nervous system to generate force production.
Naturally, you would expect that - after appropriate training - a muscle or group of muscles would be able to create a new maximal ('peak') force, and that this new peak would be associated with a higher I EMG (bear in mind that even though less neural activation is required for a particular SUBMAXIMAL force, enhancements in PEAK force are usually the result not only of upgrades in muscle size but also upswings in the ability of the nervous system to stimulate the muscle fibres). Sometimes, though, the new peak force is created without any increase in muscle size - and is entirely the result of greater neural activation (neural adaptation). When that happens, the slope of the line linking increases in I EMG with upswings in force DOES NOT CHANGE (after all, the muscle cells have not improved their quality or quantity, so a given I EMG will not lead to improved force production - and all enhancements in strength are due to an upgraded activation level, or I EMG).
What happened to the other arm
Amazingly enough, this is exactly what was observed in the UNTRAINED arm in this elbow-flexion research: Despite undergoing no training at all, the untrained arm was more than 20-per cent stronger at the end of the study! The untrained elbow flexors had tacked on not even an ounce of new muscle tissue, but they were significantly stronger, because the nervous system had an improved ability to stimulate and control their activity. Basically, the nervous system had taken the pattern of muscle control it had developed to promote strength in the trained arm and was using it to bolster strength in the still-physically feeble, untrained arm. Now that is neural adaptation!
As mentioned, the effects of activation level and intrinsic muscle change can actually be teased apart, to see which is greater. Without going into all the technical computations used by exercise physiologists, we can simply say that in our graphical representation of the relationship between activation level (I EMG) and muscle force, the more the line linking those two variables 'shifts to the right' (i. e., decreases in slope) as a result of training, the more a gain in strength can be attributed to muscular factors alone. On the other hand, if the line tends to ascend beyond previous bounds with very little change in slope, most of the gain in strength is due to neural factors.
Lessons? The nervous system plays a critically important role in the development of greater strength, and the nervous system can even learn patterns of muscle coordination and activation which can be utilized to boost strength in completely untrained muscles.
Another important study
This early, groundbreaking study demonstrated both the amazing adaptability of the nervous system and also its tremendous importance in the development of strength. An important corollary investigation completed in a different laboratory reaffirmed the notion that the nervous system is a key player in strength enhancement - and showed athletes how to develop training programmes which could optimally develop functional strength (unfortunately, this study and others like it have been almost completely ignored by the athletic community). In this second piece of research, athletes carried out eight weeks of barbell squat training and by doing so were able to increase peak barbell-squatting strength by more than 70 per cent ('Effect of Strength Training on EMG of Human Skeletal Muscle,' Acta Physiologica Scandinavica, vol. 98, pp. 232-236, 1976).
The Scandinavian scientists involved in this study had the presence of mind to measure changes in strength during other activities involving the key muscles of the legs and learned that leg-press strength also increased during the eight-week period - but to a considerably smaller extent. Most notable, however, was the fact that knee-extension strength - measured during a seated exercise which involved straightening the legs against resistance - did not improve at all over the eight-week time frame, even though the key muscles involved in knee extension - the quadriceps - had been considerably strengthened by the barbell-squatting routines.
The key to this 'strange' finding was that the I EMG (neural activation) during knee extension did not improve at all over the course of eight weeks. Thus, even though the athletes' quadriceps muscles were 'stronger', their nervous systems had not improved their ability to activate the quads during knee extensions (indeed, there was some evidence that the nervous systems were LESS skilled at activating the quads during knee extensions after eight weeks, perhaps because they had poured their energies into learning how to control barbell squatting), and thus no upgrade in knee-extension strength was apparent. The fortified quads simply sat there like slabs of beef during knee extensions; the athletes' quads were bigger but were only able to exhibit improved strength during movements which were actually practised during training (barbell squats), or during movements (leg presses) which closely resembled the practised ones. Strength did not 'transfer' between dissimilar activities (i. e., from squatting to leg extensions).
These are the key lessons
To put it another way, you can beef up your muscles all you want, but you won't necessarily be stronger in your sport unless you have done the right thing, i. e., focused on the necessary neural adaptations as well. The key lessons are as follows:
(1) the strength gained in one activity does not automatically transfer over to other activities. The transference in strength gets smaller (and may approach zero) as the activities become more dissimilar.
(2) in your training, you should focus on strengthening sport-specific movements, not individual muscles or muscle groups. If you fail to concentrate on movements, you are leaving the nervous system out, and gains in strength will not be optimized.
(3) If your sport involves running and you would like to run faster, you should try to avoid seated strengthening exercises, which isolate muscle groups, and 'two-leg' exercises, and instead focus on exercises in which strength is exerted in a coordinated fashion by one leg at a time, as is the case with actual running. One-leg squats are superior to two-leg squats, one-leg hops are better than two-leg jumps, high-bench step-ups are preferred over regular barbell squats, and so on.
Owen Anderson

[Muay Thai Elite]

Okee, ik geef toe heb alleen dit stuk gelezen:

(Eerste alinea): When a muscle becomes stronger in response to training, the gain in strength is usually attributed to an improvement in the size or quality of the muscle. The truth, however, is that strength upgrades can occur without any change in the muscle at all. Many upswings in strength are actually the result of alterations in the way the muscle is controlled by the NERVOUS SYSTEM.

Maar ik ben daar het levende voorbeeld van: als mensen me zien geloven ze niet dat ik 5 jaar thaiboks, als ze met me sparren snappen ze niet dat ik zo hard kan trappen of stoten. Geen (of in ieder geval weinig) verandering in spier (uiterlijk), maar wel mijn zenuwstelsel dus..

[DannyvK]

Dat is waar Pavel Tsatsouline het ook veel over heeft in Power to the People.. en wat Greasing the Groove is all about :)

[Bud S]

Okee, ik geef toe heb alleen dit stuk gelezen:

(Eerste alinea): When a muscle becomes stronger in response to training, the gain in strength is usually attributed to an improvement in the size or quality of the muscle. The truth, however, is that strength upgrades can occur without any change in the muscle at all. Many upswings in strength are actually the result of alterations in the way the muscle is controlled by the NERVOUS SYSTEM.

Maar ik ben daar het levende voorbeeld van: als mensen me zien geloven ze niet dat ik 5 jaar thaiboks, als ze met me sparren snappen ze niet dat ik zo hard kan trappen of stoten. Geen (of in ieder geval weinig) verandering in spier (uiterlijk), maar wel mijn zenuwstelsel dus..

volgens mij ben je gewoon een zenuwachtig kutventje

[Muay Thai Elite]

Je hebt gelijk. Ik ga weer ff trekken, dat helpt altijd wel een paar uurtjes..

[poNji]

Je hebt gelijk. Ik ga weer ff trekken, dat helpt altijd wel een paar uurtjes..

Daar komt die kracht dus vandaan.

[Jochem]

hoeveel power heb je nodig om een pincet vast te houden?

[Muay Thai Elite]

hoeveel power heb je nodig om een pincet vast te houden?

http://nobama.com/members/images/fbfiles/images/franken4.jpg

[kristel]

Moet zeggen dat ik niet het hele artikel gelezen heb. Maar neurale adaptaties zijn zeker interessant. Het zorgt o.a. voor de activatie van motorunits, verminderd co activatie en een verhoogd de vuurfrequentie. Iemand kan dus sterker worden zonder dat er (veel) hypertrofie optreedt. Het omgekeerde kan ook, dat er in korte tijd veel hypertrofie optreedt of dat er groei in de lengte plaatsvindt, maar dat iemand niet veel sterker wordt. Denk aan de puber die ‘onhandig’ beweegt of de sporter die in korte tijd erg in spierweefsel is toegenomen, maar dit nog niet goed kan gebruiken.

[Jochem]

uuhh, que, waar zijn de posts van MTE. zijn zijn oude posts ook gedelete, dacht dat ie er alleen niet meer kon opkomen. AAh, ach, zal allemaal wel. laat mijn ontopic reactie hierop ook maar zitten ook.