FOCUS
02-09-2009, 15:11
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.
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.