August 30, 2010

Basic Tips Every Lifter Needs To Know About The Nervous System

Understanding the nervous system and the role it plays in terms of performance is the single most important concept there is regarding strength training. Unfortunately, most don't have the slightest clue about how to consciously utilize it to their advantage. Fortunately, even the least knowledgeable person can quickly develop a brief understanding of how the nervous system works as it relates to performance, as long as it’s presented in the right manner.

The nervous system is what controls how quickly, and how many motor units are recruited when you deliberately lift a weight. Each motor unit has a series of muscle fibers assigned to it based on its makeup of whether they are fast twitch or slow twitch. High threshold motor units include fast twitch muscle fibers and low threshold motor units include slow twitch muscle fibers. If maximum strength/performance, or hypertrophy is the goal, then recruiting and fatiguing as many motor units as possible is of primary importance.

The first thing anyone ought to know to better understand the nervous system as it relates to performance is that motor units are recruited as they are needed, and they won’t be called upon unless absolutely necessary. So the question becomes, how do you ensure that as many motor units are recruited as possible?

Put maximal weight on the bar – The heavier the weight is, the more force that will be required to lift it, resulting in more motor units being recruited.

Intend to lift with maximal speed – It is the intent that ultimately determines how many motor units are going to be needed to complete the task at hand, regardless of the amount of weight being lifted. The faster one attempts to lift a weight, the more motor units that will be required to generate the force desired.

The brain assumes that the task at hand is difficult because the conscious intent is to use as much force as possible, therefore it will send as many high threshold motor units as needed to ensure that the task is completed.

Pairing agonists and antagonists together (e.g. chest/back, biceps/triceps, quads/hams, etc.) – Opposing muscle groups are recruited when lifting a weight to create a stable joint (also termed ‘co-contraction’), but this can result in lower force output because, if one muscle is contracting to produce movement but the opposing muscle group is also contracting to create stability, then it will provide unwanted resistance which negatively affects how much weight can and will be lifted. By recruiting, and even exhausting the antagonist prior to performing a movement for the agonist, there will be a greater level of net motor unit recruitment in favor of the agonist as a result of decreased antagonistic co-contraction. Basically the same amount of motor units will still be sent to the agonist, while a lesser amount is sent to the antagonist, which logically would mean that more force can be produced.

A practical example of this principle in action would be to do a set of barbell curls prior to a set of lying triceps extensions, and go back and forth in that fashion until completing the desired number of sets. In this case, each muscle (the biceps and triceps respectively) would benefit by being able to generate more force because the opposing muscle group will not be contracting as much due to acute fatigue.

Explosive movements like plyometrics, or the Olympic lift variations, prior to your intended movement – The nervous system, like the body, operates in a reactive manner in that, if there is a necessary demand to heighten its awareness, or increases its potential to react, it will remain operating in a heightened state for a prolonged period of time after the demand is removed. It’s not like flipping a switch on and off, it stays on for a while once it’s turned on. This opens the door for a wide range of possibilities to enhance performance in a relatively simplistic manner.

For example, due to their explosive nature, performing a set of 3 or 4 jump squats prior to a set of squats is a good way to let your brain know that it needs to be ready to recruit as many motor units as possible in a way that is specific to the movement that you’ll be doing. This way, when you get under the bar to perform your set, the weight may feel lighter by contrast, which means you’ll be able to either perform more reps, or use more weight, or even use the same weight but lift it with more velocity (meaning more force is being exerted). There is a limitation with this technique though in that it is only really suitable for those lifting in rep ranges under 6, as any more than that will be limited by metabolic fatigue, irrespective of how fired up the nervous system is (one technique can only take you so far).

Plyometrics, and the Olympic lift variations, are great for activating the nervous system and prompting it to recruit the high threshold motor units, and the greater amount of high threshold motor units that are active, the easier the lift will be to complete as they are capable of generating the highest levels of force. They are also the least fatigue resistant, so once again, this technique is primarily effective for those training with heavy weights and low reps, as high reps more so rely on metabolic factors, not neural factors.

Supramaximal holds – Motor units being recruited as needed is not limited to full range of motion movements at all, and can actually be done by holding a greater amount of weight than would be possible to perform through a full range of motion at end range for a short period of time.

An example would be to put 10-20% more weight on a bar than you can lift and hold it there for 10-15 seconds. Obviously the heavier the weight, the lower duration the hold will be, but doing so will build confidence in that you’ll develop a feeling for what a heavier weight feels like without it crushing you, and by contrast your working weight will feel substantially lighter. The only major downside to this technique is that strength is gained in the range that it's trained, so be sure to use isometric contractions at various ranges of motion to maximize the adaptation.

The reason for this is because of what’s called post-tetanic facillitation. What that means is that your nervous system will be tricked into thinking that it’s going to need to lift the supra-maximal load, and will stay ramped up for a few minutes following the isometric hold. You can take advantage of this by putting on your working weight, and because your brain will be expecting to lift a far greater amount of weight, it will feel light (think of picking up a glass of water that you think is full, only to find out it’s close to empty – generally the glass is lifted with more force than is needed and you end up spilling water because it was lifted with too much force).

This technique is similar to what baseball players do before they go to bat. If you’ve ever been to a baseball game, you may have noticed that the batter on deck (which means next up to bat) is practicing his swing with an additional weight attached to the bat, that’s heavy enough to make him swing with more force, but light enough that it doesn’t affect the movement pattern. After removing the weight when it's his turn to bat, the bat feels lighter by contrast without the additional weight on it, and he is able to swing it with more force. If the bat is too heavy however, there will be a greater amount of deceleration needed at the end range of the swing, and this is not a good thing at all, because it could throw off the mechanics of the swing, and essentially make him worse, not better.

Supramaximal eccentrics – This is identical to supramaximal holds, only in this case you perform one eccentric repetition by not just holding the weight at lockout, but lowering it. Obviously this is only recommended if using a barbell in a power rack so that the pins can take the load off after reaching the end of range. The benefits of performing an eccentric repetition with a supramaximal load over just holding it at lockout is that a greater number of high threshold motor units are recruited during an eccentric contraction as the body’s way of preventing catastrophe as best as possible, which is not only beneficial from a performance perspective, but a hypertrophy perspective as well.

Doing exercises seated or standing, uni-laterally or bi-laterally will also affect recruitment – Every little modification to an exercise has downstream effects in terms of recruitment, which you can use to your advantage depending on what your goal is. If the goal is to lift more weight, then you’re going to want to perform exercises in a manner in which there is the greatest level of recruitment systemically. If the goal is to enhance the level of activation locally in a specific muscle, then you’re going to want to limit the amount of recruitment to other parts of the body.

For instance, when standing, it’s possible to curl more weight by using a little body English which suggests a greater level of systemic recruitment, but that doesn’t necessarily mean the targeted muscle group (biceps) will be placed under more tension. More systemic recruitment means more systemic development which is fine if that’s your goal, but it doesn’t necessarily mean the biceps will grow as much as if you performed the exercise in a manner in which a greater percentage of the load was directed upon the biceps, like being seated, and using dumbells in which you perform one arm at a time.

When seated, there is far less recruitment to muscles like the lower back, calf, and quad, and therefore a greater percentage of motor units can be sent to the biceps, as it is much easier for the brain to focus on directing as much attention to that area as possible when others are essentially eliminated from the movement by default of positioning. While you will not be able to lift as much weight, because it is essentially harder to "cheat", percentage wise there will be more local recruitment, which would positively affect muscular development.

While those are just a few ways to enhance recruitment of the high threshold motor units, simply recruiting them isn’t enough if maximizing strength or hypertrophy is desired. Motor units need to be fatigued to be trained, therefore the need for repeated efforts is of primary importance.

This is where things can get tricky because the high threshold motor units, and associated fast twitch muscle fibers, have a limited time to which they can remain active. If they aren’t recruited enough times during a training session to become fatigued, you won’t attain the desired result (maximum strength or hypertrophy), at least in an optimal amount of time.

Due to their short shelf life in which they remain active, it is essential to perform a high volume of work using any, or all (not suggested), of the techniques outlined above during a training program. The more you fatigue the high threshold motor units, the more efficient you’ll become at recruiting them, thus making the adaption more permanent.

Putting it all together

Here’s a brief example of how to sequence the techniques above to best utilize them:

A)   Explosive movement OR Supramaximal hold/eccentric to potentiate the nervous system
B)   Heavy movement for agonist alternated with antagonist to maximize recruitment
C)   Stabilized movement (either seated, or using a machine) performed uni-laterally

The template above is obviously a very incomplete template, but its purpose is to show when or where each technique listed above would be best suited.

There is a time and place for any, and all of the concepts presented throughout this article. If you are unsure as to how to use any of the techniques discussed, or when during a training program they would be best suited, feel free to contact me at and I'll help create clarity for any questions or concerns you may have. I'm available for online consulting and personalized program design, as well as one on one training if you are located in the Greater Toronto Area (GTA). These techniques are not for beginners, so don't attempt them if you have no idea what you're doing.

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