During and following a set of a particular exercise, the muscle has to firstly relax and contract a number of times, and then relax totally while it readies itself for another set. Still, it doesn't end. The nervous system response to a particular stimulus (a weight for example) should strengthen given the requisite amount of rest and quality of nutrition.
It then follows that three main neuropsychological processes should occur before a training session could be considered productive:
- The propagation of a neural response to a stressful event
- The relaxing of the muscle following each contraction and between sets
- The strengthening of the neural response as the body adapts to continued stress.
Technically speaking, the neuropsychology underpinning weight training is the most crucial aspect in developing a great body. Without an appropriate nervous system response to a particular stimulus, lifting would be extremely hard, if not impossible. The remainder of this article will explain exactly how our neurology dictates the outcome of our training programs and the ways to promote its efficiency.
What Happens During A Set?
The nervous system, comprised of billions of neurons, is ultimately responsible for the communication between cells (neurons). This includes the muscle and brain cells. Before one can lift a weight, a neural response must occur in the brain. Depending on the strength of the particular pathway governing this response, the weight will be lifted and lowered, with no adverse effect.
To be more precise, a nerve cell (neuron) will process the information it is provided with (a weight to be lifted) and will respond accordingly. Neurons act like any other cell in terms of their ability to grow, proliferate, and undergo processes of diffusion and osmosis in their membranes.
However, unlike other cells, they process information. The special properties of the neuron and its connection to other neurons (forming a neural chain) will dictate its ability to lift a certain weight for a certain number of repetitions. This may defy conventional thinking that posits muscle as being the limiting factor as far as lifting a weight is concerned.
What really happens follows:
- At the conception of a set of reps, the brain receives instructions to propagate a nervous impulse.
- An electrical signal (action potential) is engaged.
- The action potential (going from the body to an axon [a branch off which information is released] inside the brain) causes a reversal of charge (depolarization) within the neuron.
- This depolarization electrically charges the neuron due to electrically charged ions flowing from one side of the neural membrane to the other.
- An action potential ends at a pre-synaptic junction (the junction is between the end of one neuron and the beginning of the other) where it causes neurotransmitters (chemical messengers) to be released and the process of synaptic transmission commences (essentially communication between neurons). (An excellent synaptic transmission site can be found at http://www.williams.edu/imput/synapse/index.html).
- Neurotransmitter release, if effective, will cause an excitatory post synaptic potential (EPSP) and this will ensure that another action potential will commence, and so on, from neuron to neuron.
- The wave of depolarization that is the action potential combined with successful pre-synaptic transmission will ultimately cause the muscle to . Up to one-thousand action potentials may be needed to complete one repetition. It should be mentioned that a refractory period occurs after each depolarization. This sometimes lasts for as little as 0.001-0.002 seconds before another action potential can occur, thus allowing 500-1000 impulses (action potentials) per second.
Under normal conditions the action potential will terminate (stop) on a post-synaptic neuron. With weight training, and any other physical activity for that matter, an action potential will terminate on a specialized structure called a neuromuscular junction.
The axon, which branches off at the end of a neuron, will then subdivide into a number of terminal buttons (post synaptic junctions). These buttons will release neurotransmitter onto the motor end plate and a contraction will occur following another equally complex process (another article?). The particular neurotransmitter used at the neuromuscular junction is called acetylcholine.
Neuropsychological Implications For Bodybuilders
For a nerve impulse (action potential) to occur successfully and efficiently (at greater speed), the sheath that covers each nerve should be functioning at an optimal level. This nerve sheath is called myelin and its main purpose is to allow rapid and efficient transmission of nerve impulses along the nerve cells. If myelin is damaged or under-functioning, the impulses are disrupted.
Multiple sclerosis is caused from this occurring.
While multiple sclerosis is an extreme from of nerve transmission disruption, and most of us need not worry about this, myelin health is still important. Given that myelin governs efficient nerve transmission, and resultantly, muscle strength, it is important to protect it. A correct diet containing a full spectrum of vitamins and minerals and more importantly essential fatty acids (EFAs) will help to protect myelin.
In a non-bodybuilding related study, Lozoff and researchers from Chile conducted research into early lack of iron and its effect on the myelin integrity of a child's brain. Their findings caused them to believe that a lack of iron in infancy disrupts the production of myelin in a child's brain. "Iron deficiency can really have a cumulative effect as these really fundamental processes are being laid down," Lozoff said.
To keep neural impulses firing efficiently, weight training on a regular basis, with variation and, importantly, progressive resistance principals employed, is imperative. Neural recruitment occurs when a number of muscle cells contract at once. The nervous signals from the brain then reach a certain percentage of the cells inside a muscle. The number of 'recruited' muscle cells increases from session to session.
The aim is to recruit as many muscle cells as possible. Progressive resistance training subjects the muscles to a greater stress and as a result the neural pathways adapt favorably. The neural response increases with continued progressive resistance style training.
Acetylcholine, a neurotransmitter involved largely in the neuromuscular response, can, at times, need replenishing. Aged people in particular may need to restore acetylcholine levels. Neuronal acetylcholine levels can be restored through the use of certain supplements:
Acetyl-L-Carnitine, Alpha GPC,
There we have it. Weight lifting is not as simple as many may think. The underpinning neurological processes governing muscle contraction and relaxation are important to consider given that they control how our muscles response to the training stimulus. Correct diet, progressive resistance training and supplementation, if required, are key imperatives to improving neuronal health.
- King. M.(2003). Biochemistry of neurotransmitters : [on line] http://www.indstate.edu/thcme/mwking/nerves.html#catecholamines
- Rodriguez M. (2003). A function of myelin is to protect axons from subsequent injury: implications for deficits in multiple sclerosis. Brain. 126 (4) pp 751-752.
- Lozoff, B.(2001). Presentation to the American Academy of Paediatrics and Paediatric Academic Societies.
- Levitan. I. B. & Kaczmarek. L. K.(2001). The Neuron: Cell and Molecular Biology (Third Edition). OUP: GB.
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