I want to continue from my discussion of the stretch shorten cycle previously to discuss the contribution of neural factors to strength performance. At the end I’ll try to summarize this mess.
Neural & Muscular Factors in Strength Performance
Back in the very early days of the study of strength training, an observation was made that people’s strength went up far more quickly in the early stages of training than their muscle size. Quite in fact, it was often observed that strength increased fairly significantly before any measurable muscle growth had occurred. This indicated that there was some other adaptation, usually taken as neural/neurological (because there isn’t a hell of a lot else that it could be) that was occurring to explain it.
At the most extreme, it was felt that all of the gains in strength were neural although this is kind of questionable: protein synthesis goes up after the first workout even in beginners and it would seem unlikely that there was no increase in muscle size occurring at all.
Certainly it could be that beginners ramp up muscle protein breakdown initially (and an interesting new paper suggested that the early increase in protein synthesis isn’t related to growth since it’s repairing damaged tissue) so that the effect is cancelled out. Just as likely is that the technology that was available at the time wasn’t sensitive enough to pick up relatively small changes in muscle size that may have been occurring.
Irrespective of this it’s clear that at least some fairly major part of the initial strength gains is due to neurological adaptations. It may not explain 100% of the changes in strength but something is happening. To look at some of what is happening along with what can be accomplished later in a training career, I first need to run through the neural control of movement.
Neural Control of Movement
To understand the rest of this piece, I want to briefly discuss the neural control of movement. Note that this will be very simplified, all of this physiology is just too many years ago and the details, honestly, aren’t that critical outside of broad stroke stuff. Get a textbook if you want to really fill your brain up with trivia about calcium release and reuptake and ion channels and such.
There are two major types of movements that can occur in the body. The first are reflexes, they operate from the muscle to the spine back to the muscle with no voluntary control involved. That’s why they are reflexes and they act more quickly since they don’t require the brain to operate. I mentioned those briefly last week when I talked about SSC and they role they may play there and won’t re-discuss them here.
Rather I want to focus on voluntary movements, the ones that you make through conscious effort. As your eyes scan from left to right reading, that’s a voluntary effort. As you move your hand to the mouse to click the close window button because I’m boring you, that is too.
Any sporting movement of note is also a voluntary movement (though they may have a reflex component to them). These initiate in the brain when the motor cortex sends signals down the motor nerves which terminate in the neuromuscular junction (NMJ) at the muscles.
Note: The combination of a motor nerve and the muscle fibers it activates is called a motor unit (MU). Any given MU may include anywhere from a few (like 10) up to thousands of muscle fibers and it’s the sum total of the fibers/their total cross sectional area in any given MU that will determine how much force potential is available. Even though it’s not strictly correct, I will use muscle fibers and MU interchangeably, ok? Ok.
Anyhow, the neural signal hits the NMJ and a bunch of stuff (a technical term) happens. Choline gets released among many other things and, well, go look it all up if you care and the end result is that the muscle fibres contract to one degree or another.
In the most general sense, just think of it like an electrical signal that brain sends signal to the muscle which then contracts. If you really care, watch this Schoolhouse Rock video which was at one point apparently the most watched video in medical school since this stuff is so hard to understand.
Note: When I wrote about muscle size and strength performance, I should have talked a little bit about muscle fiber types. There are, grossly speaking, two fiber types which are Type I (red fiber, slow twitch) and Type II (white fiber, fast twitch) with a number of sub-types (having to do with myosin heavy chains such as IIa, IIx and stuff).
For reasons having to with enzymes and mitochondrial density and such, Type I fibers are more enduring while Type II fibers are more for power and strength performance. Surprisingly, most (but not all) data shows that Type I and Type II fibers actually produce the same force per unit cross-sectional area. Since type I fibers are usually smaller than Type II, they produce less total force on average.
Neural Control of Force Production
Anyhow, enough of that, in a gross sense, there are two ways that the body controls how much force a muscle produces and those are rate coding and fiber recruitment.
The concept of rate coding is fairly simple so I’ll deal with it first. Just think of it as the speed with which the brain is sending signals to the muscle/MU. Technically speaking a single signal could be sent, this causes what is called a twitch in the muscle fiber and generates a small amount of force.
As signals come faster, the muscles contracts with more force and eventually what is called a tetanus occurs. At this point the MU fires maximally and even if more signals were sent the muscle can’t contract any harder even if more signals (such as from electrical muscle stimulation) are applied.
The concept of recruitment refers to the number of muscle fibers/MU’s which are being actively fired to generate force. As more MU’s are recruited, more force is produced and I guess it’s worth mentioning something called Henneman’s Size Principle (not to be confused with Henneman’s Wife’s Size Principle which has to do with length versus width but that’s a whole different kettle of fish) here.
This refers to the idea that MU’s recruit in order from smaller to larger during voluntary movements. So smaller (and by definition less force producing) MU’s/muscle fibers (generally Type I fibers) fire first and as more force is needed, larger and larger MU’s are recruited (generally Type II fibers).
This actually isn’t a universal phenomenon. There is at least some evidence that high-threshold/larger MU’s recruit preferentially during eccentric movements. Electrostimulation (EMS) may also recruit muscle fibers in a reverse order but this is because they are bypassing the normal voluntary nervous system function.
As well, in reflex actions, high-threshold/Type II muscle fibers may preferentially recruit. There is something called the cat paw shake reflex that shows this: put a piece of tape on a cat’s paw (fun for the whole family) and it will shake it rapidly back and forth and will preferentially use Type II muscle fibers to do so.
And in perhaps one of the funniest bits of nonsense I have ever read on this topic, some folks once argued that if you practiced something (like a power clean) enough until it became a reflex the same could happen. But it simply doesn’t work that way as no voluntary activity can ever become a true reflex. At most it becomes relatively automated in that you don’t have to think much about what you’re doing and you’re never recruitment Type II fibers first in a movement like this no matter what you do. Anyhow.
How Rate Coding and Recruitment Affect Strength Performance
The human body actually uses different combinations of rate coding and recruitment to generate force depending on the muscles involved. For large muscles, basically anything of relevance to the weight room, it will use recruitment up to about 80-85% of maximum force and then use primarily increases in rate coding beyond that. Put differently, above 80-85% of maximum force (think 1 repetition maximum) you’ve recruited all the fibers you can recruit (see below) and further force output occurs due to increases in rate coding.
But in smaller muscles, like those of the hands and the eyes (called constrained muscles for some reason), the body only uses recruitment up to about 50-60%% of max and uses rate coding from that point on. The reason is that modulating rate coding gives far more precise control over force production than recruitment and it should seem somewhat obvious why this would be used for small muscles. If it didn’t, your eyes would swing wildly from side to side without precise control and you’d lose fine motor control over your fingers. You couldn’t read this OR close the window when you get bored.
I bring this up as it’s not uncommon for people in this field (unaware of this VERY basic bit of physiology) to use studies on finger muscles and attempt to apply them to all muscle movements. A common example are studies showing that women have better isometric endurance than men in their thumbs which simply does NOT translate over to something like a bench press.
Yes, in some situations, women still have better endurance than men but it’s exceedingly context specific and you still can’t apply a study in the thumbs to a bench press or whatever. But that’s a topic for another day/article/book.
I’d note that the above primarily holds for slower or isometric contractions. In fast contractions, you get near maximal MU recruitment as low as 33% of maximum force/load since fast contractions recruit three times as many motor units to get the high initial peak force that is required.
Neural Adaptations to Training
With the above out of the way, let me move on to some of the neural adaptations that can occur in response to training. There are a host of them and I’ll probably miss some of them as, once again, I’m simply not completely up to date on this literature. I’m sure some things have changed but so be it. Here’s a good review paper that you can read if you want to get up your butt and it talks about most of what I’m going to present below in highly technical detail.
Rate Coding Adaptations
In that it appears that average rates of rate coding (sometimes called discharge rate) are lower than the maximal potential to generate force, adaptations here are one possibility to increase force output and strength performance. And the discharge rate of neurons has been shown to increase with training, increasing force output with no change in any other factor. So this can adapt with training.
Other potential adaptations may occur as well. One is called a doublet, basically two neural signals that get sent closer to one another than usual but there are assuredly others. Some of the changes here, the body being able to send more signals faster are likely to be involved in improving rate of force development (RFD, how quickly force can be developed).
Generally speaking, high-speed movements tend to improve this and much of the effect is likely through neural means, the body becoming more efficient at turning on muscles more quickly. This includes things like jumping/plyometrics, the Olympic lifts, ballstic movements like medicine ball work and even high speed traditional weight lifting (this has some physics issues associated with it having to do with deccelerating at the top).
Even if the speed of the lift is slow, an intent to move quickly can improve RFD as the body is attempting to generate force quickly (heavy weights simply don’t move quickly). Even isometrics done in such a fashion as to go from relaxation to generate as much force as quickly as possible can “train” the nervous system to generate force more quickly.
It can also train relaxation, the ability to let muscle fibers turn off quickly since you can alternate between generating high forces quickly and relaxing just as quickly. For things like sprinting where you have to switch muscles on and off very quickly, this is critical.
Fiber Recruitment Adaptations
Moving back to muscular fiber recruitment, I want to address one of the biggest pieces of nonsense that has been rattling around the training worlds for a few decades. And that piece of nonsense is that the body can only recruit 30% of its available muscle fibers and/or that one of the major neural adaptations are huge improvements in the ability to recruit fibers. I’m not sure where this came from but it’s been around for so long I suspect it was just inferred early on from the observation that people gained strength faster than they gained muscle size. But it’s simply not true.
One of the ways that this is tested in the lab by using something called the Interpolated Twitch Technique (ITT). What’s done is that they have people do a Maximal Voluntary Isometric Contraction (MVIC, just think of this as 1 repetition maximum for all practical aspects) first by itself and then with electrostim applied to the muscle.
Since by definition rate coding and voluntary recruitment will be maximal under these conditions, any increase in muscle force is taken to represent increased fiber recruitment (since the electrostim is applied at the muscle, it can’t be altering rate coding).
And studies clearly show that even untrained individuals can recruit nearly 100% of their arm muscles and nearly 90%+ of their leg muscles during both maximum isometric and dynamic contractions. Oddly, low back muscles may only fully recruit 70% of total fibers and I have no idea why this is (it’s probably a safety mechanism to avoid excessive forces on spinal disks). Some feel that this is an overestimate and put the values a bit lower like 75% but, regardless, the idea that we can only voluntarily recruit 30% of our total muscle fibers is absolutely, hilariously wrong.
Make no mistake, there may be some slight potential to improve recruitment, especially if the true value is closer to 75%, but it’s still not huge and probably isn’t the major neural adaptation occurring overall. It’s also been suggested that the body keeps a reserve set of fibers that it can’t recruit except under extreme conditions but the literature I linked to above doesn’t support that.
Note: The above may also be untrue for finger muscles where small increases in recruitment (like 7%) have been measured. Just another place where the hand muscles just aren’t the same as the major muscle groups in terms of their physiology and why data on them simply can’t be applied to most large muscle group exercises (I guess if you arm wrestle).
Technique/Coordination and Strength Performance
In the broadest sense, a lot of what is occurring neurally, especially in the early phases of learning a new movement, is that it becomes more coordinated and/or technique improves (depending on how you want to look at it).
This has to do with all of the changes in the motor cortex that go into learning how to fire the muscles in the right order and at the right speed. You can watch this happens as a child starts to crawl, toddle and then walk where they are first very unstable but over time everything becomes coordinated.
Even in the weight room, if you ever train a rank beginner on any sort of complex movement, even something like a dumbbell bench press, you will notice from workout 1 to 2 that their technique and coordination improve by leaps and bounds. If you were to test them for maximum strength, which I don’t recommend since the numbers would be meaningless, it would go up from workout 1 to 2.
Related: How Should Beginners Train in the Weight Room?
Clearly they haven’t gained muscle and it’s unlikely as hell that any other neural adaptation has occurred. What has happened is they have become more coordinated and their technique has improved. And this continues for some time as they gain relative mastery of the movements (over more and more time, the action may become automated).
Researchers figured out fairly early on that there is often a strength gain from the first to second workout in beginners and this is the primary mechanism. It’s why a lot of more modern studies will use a 2 or more week acclimation phase to get everyone through at least the baseline learning phase of new movements so that those very early changes aren’t the big reason for the improvements.
Practically, it also makes an argument for giving beginners less complex movements early on (machines have the least coordination requirements while something like a back squat, deadlift or god forbid the Ol’s have the largest). I can’t find the paper at the moment but more complex movements may take longer to generate growth than simpler movements simply because it takes longer to get coordinated/through the neural adaptations so that muscle growth predominates.
It’s also a good reason for beginners to do the same movements more frequently as a lot of this is simply a practice effect. This is one of several potential benefits to training beginners with full-body two to three times per week workouts on the same movements: they get more practice and technique improves faster.
Lately there is a shift even among more advanced athletes to train a given lift more frequently. Olympic lifters have done this for decades as their sport requires immense technical practice but even powerlifters are doing this to one degree or another (and will do so until training shifts back towards intensity again in a few years).
Inter/Intramuscular Coordination Adaptations
Another potential adaptation has to do with two semi-related factors which are inter-muscular and intra-muscular coordination. The first refers to the coordination of fiber contraction within a given muscle fiber (the review paper I linked above calls this MU synchronization). In order to generate maximal force, for example, fibers should all fire at the same time or close to it.
They don’t always do this and often, usually to improve endurance, fibers will kind of switch off between which is generating force at any one time. One group fires and then shuts off while another group fires. In this vein, one study found that weightlifters show better muscle fiber synchronization than untrained men or musicians and, presumably, this is due to differences in training. Of course, musicians are doing very fine movements often for long periods and it would make sense that the overall neural adaptations would be different.
Intra-muscular coordination refers to coordination between different groups of muscle. This has to do with timing and firing of the muscles since most activities of relevance involve movements around multiple joints. In a squat, the quads, hamstrings, glutes, low back all contribute in different ways and at different parts of the movement.
In the bench, it’s pecs, serratus, anterior deltoid, triceps, lats, etc. all firing in sequence at one point or another in the movement. Properly performing these movements means not only improving the inter-muscular coordination within each muscle but the intramuscular coordination between muscle groups. Most of the adaptations here are simply due to practice.
Co-Contraction and Antagonist Disinhibition
Another aspect of coordination has to do with co-contraction and antagonist disinhibition. So at the elbow you have biceps on one side which flexes the elbow and triceps on the other which extends it. Now the muscle driving the primary movement (i.e. biceps in a curl) is called the agonist and the muscle that is working in the opposite direction is the antagonist.
And it turns out that in a lot of movements, the body fires both to one degree or another. So when the biceps is trying to curl, the triceps may be contracting against it. And this means that less net force (ok, torque) is seen around the elbow and less weight can be lifted: the triceps is fighting against the pull of the biceps.
It’s arguably more typical to see co-contraction in more compound movements and sometimes this is really important as co-contraction works to stabilizes the joint. For example, co-contraction of quadriceps and hamstrings at the knee in activities like jumping or landing is critical for knee health for example and one contributor to the roughly 3-9 times as many ACL injuries in women is that women’s hamstrings fire every so slightly slower than the quads during things like jumping and landing.
It’s not by much, around 100 milliseconds but this is long enough for the quad to pull on the shin (causing anterior shear) and potentially stress the ACL. If several other factors are present such as a narrow notch for the ACL to pass through, this can cause the ACL to be basically be cut.
But with training, sometimes this co-activation DECREASES, what is called antagonist disinhibition. So the antagonist muscle which is opposing the prime mover/agonist doesn’t fire as hard. While this might not be as good from the standpoint of joint stability, it increases force output around the joint since the antagonist isn’t opposing the force production of the agonist. Presumably the nervous system effectively ‘tunes’ this over time to provide a decent balance between force production and stability.
Implications of Neural Adaptations for Strength Performance
In the first part of this series, I mentioned that muscle size (cross-sectional area) really only gives the strength potential of the muscle and the existence of all of these neural factors explains why. A large muscle that isn’t firing maximally or in a coordinated fashion may generate less force than a smaller muscle that is.
For this reason you can conceptually think of force production as:
Force output = Muscle XSA * Neural Factors
We might put biomechanics in there but since they are unchanging for any given individual, the above are the two factors that are typically considered (I would probably put SSC factors under muscle).
So consider the following situation: two people, one of whom trains purely on isolation movements for growth (a bodybuilder) and one who trains purely on compound movements (a powerlifter). The bodybuilder may very well be larger but if you have him bench press the smaller guy, he may lift less.
Having not practiced the movements (especially not with heavier weights), he won’t have the various neural factors ranging from technique to inter/intra-muscular coordination to maximized rate coding, MU synchronization, etc. that the smaller guy has.
Mind you, give that bodybuilder a few months to train on the more complex movements with heavier weights and he’s likely to crush the smaller guy poundage wise: he will have taken his existing muscle mass/strength potential and developed the neural factors to optimize their function.
By the same token, someone who has developed their neural factors to a great degree, usually due to a steady diet of nothing but low repetition, high-intensity work (without the volume to generate growth) often hit a point where the only way to make strength gains is to gain muscle size. That gives them more strength potential which can then be further maximized with neural training. I’ll discuss the implications of this below.
Improving Neural Factors
Before continuing let me make it clear that with the occasional weird exception always trains both muscle and nervous system. Since the latter makes the former work, you simply can’t separate the two under most conditions. At best whether you’re putting more stress on the muscle or neural factors is a matter of degrees and it’s generally accepted that certain types of training put relatively more stress on muscular or neural factors.
Perhaps better stated is that different types of training put different types of neural stress and that any given individual is looking at wanting to generate adaptations and optimizations relevant to their activity. Increasing rate coding and maybe recruitment is different than improving RFD or relaxation.
In that there are different types of neural adaptations, presumably there are better and worse ways of improving each one. And in the most general sense, generating neural adaptations is about training in such a way to force the nervous system to act in a certain way: over time it will adapt in a specific fashion to that stimulus.
I mentioned some of these above, rate of force development (and probably some aspects of rate coding) are trained by doing high-speed movements of varying types. This requires the body to activate muscles quickly and over time it becomes better at this: the body learns to generate force more rapidly (it often learns to relax rapidly as well which is important for sports such as sprinting).
Technique and various aspects of coordination are improved with technical practice and repetition and the trend of performing complex movements more frequently (within limits and while keeping intensity under control to avoid connective tissue injury) will facilitate that. Of course, it’s important to actually practice proper technique in the first place.
Related: Should I Change Exercise Technique?
Practice may not make perfect but it tends to make permanent. Imaginary contractions even work here since the motor cortex can’t really tell the difference between an imagined movement and a real one. Some studies have shown that imagining practicing a movement improves it (usually skill stuff like basketball) as much as actually practicing it. The same can hold for strength training although it’s important to know what proper technique is first before this is done.
Looking at other factors such as the potential to increase recruitment or rate coding in general, so-called “neural” training at least for maximum strength has generally thought to entail working above 85% of maximum (roughly 5 repetitions or less) with fairly varying volumes and frequencies. Again, this still involves the muscles (often very heavily) but a primary stimulus to the body is to improve neural factors. Since it maximizes recruitment and forces rate coding to increase, working above 85% tends to be more neurally dominant while working below that is more muscularly stressful.
It is interesting to note that some of the recent work comparing higher lower repetition ranges tends to find that both may work similarly for growth (if some aspect of training volume is equated) but the low rep training increases maximal strength more. Of course, strength is being tested as maximal strength and it makes logical sense that you need to practice what is being tested.
But practice is part and parcel of many of the neural adaptations in the first place. The body adapts in response to the stresses put on it and if it is forced to generate maximal forces through maximal recruitment and rate coding in complex movements requiring high degrees of inter/intra-muscular coordination, well…that’s what it will improve at. Even training with higher repetitions to failure, even if the stimulus is similar for the muscle fibers, isn’t the same to the nervous system.
Summary of Factors Impacting on Strength Performance
Ok first let me summarize the 4 major factors I’ve described that go towards determining strength performance
Inherent Biomechanics: This includes limb length (which determines lever arms) and things like where muscles attach to the bone. This is unchangeable outside of whatever limits exist for modifying exercise technique to either take advantage of good biomechanics or limit the impact of poor biomechanics.
Muscle Cross Sectional Area: The physiological cross-sectional area (XSA) is a primary determinant of force production as it represents the cross section of the individual muscle fibers that can generate force. Fiber type plays a role here with folks having more Type II fibers having more strength potential than folks with more Type I (who are more enduring).
Average people tend to have about equal percentages of fiber types in most of their muscle (women may have slightly more Type I fibers than men) but elite athletes are often found with extremely skewed percentages with good strength/power athletes having lots of Type II fibers and endurance athletes lots of Type I fibers.
For decades it was stated that you couldn’t really convert Type I to Type II fibers or vice versa. It’s turning out to be a lot more complicated than that for reasons I don’t want to get into. Big picture, those transformations are likely to be small and mediated by the conversion of what are called intermediate fibers based on the training done. But more research may change this model in the future.
The Stretch Shorten Cycle (SSC): Being comprised of a number of factor including reflexes, force storage and return by the elastic component (connective tissues) and having longer to generate force (due to pre-activation during the eccentric).
This can be trained with practice and plyometric or SSC exercises due to changes in connective tissue and reflexes but note that changes in connective tissue structure and function takes a LONG time. We are talking months or years here.
It can’t be rushed and trying just makes people break. Many movements in the weight room can’t really take advantage of it (i.e. deadlift starts without pre-stretch and a paused bench press may or may not get a benefit).
Neural Factors: Used here to describe a host of different factors including (potentially) fiber recruitment, changes in rate coding, inter/intra-muscular coordination, decreased antagonist disinhibition and probably others this describes how the muscle fibers which exist are fired, or simply automating voluntary movements with technical practice. Specific training that forces the nervous system to fire in a certain way will tend to cause the desired adaptations.
Implications and Application for Strength Performance
It would seem kind of pointless (although not outside of the realm of the stuff I write) not to include at least some practical aspects of this information. So here’s a few observations applications of all of this stuff.
Perhaps the first is this: while there is a general relationship between size and strength (in terms of weight on the bar), it’s not universal. Differences in mechanics, tendon insertions, and neural factors often allow a smaller (or smaller looking) person to lift bigger weights than the larger person (this isn’t universal of course and, generally, strength and size will scale to one degree or another).
Shorter limbs mean shorter lever arms (and there’s a reason top benchers and squatters and even OL’ers tend to be built along fairly similar body types) and if they happen to have different tendon attachments, this also impacts on how much weight they will end up lifting.
If they are neurally very efficient (and percentage fiber type can interact with this), they may very well lift bigger weights than a taller and larger person. It can be demoralizing for both as the smaller guys sees that he’s stronger (but visually smaller) than a bigger guy or for a bigger guy to wonder why that little guy can move more weight.
Coming directly out of this, it’s often said that progressive tension overload is the key to growing bigger and stronger. This is true but it’s critical not to confuse weight on the bar with progression per se. As above, a smaller guy may bench 315 while a smaller guy benches 275 and there doesn’t seem to be a relationship between muscle size and strength.
What’s important to either lifter individually is that they make strength gains over time (and, as Dante Trudell so eloquently put it “Growth occurs due to strength gains in moderate repetition ranges”). Put differently: comparing how much two different people can lift isn’t relevant here. Rather, what’s relevant is comparing what any one individual is lifting now versus weeks or months or a year from now.
Due to the combination (generally) of muscular and neural factors in determining strength, it’s usually felt that you can at least preferentially adapt one or the other. Yes, as I wrote above I know lots of low reps sets build size and obviously higher rep sets have a neural component and it would be silly to think otherwise.
But if the goal is to maximize strength without making gains in muscle mass, focusing on lower repetitions with a reduced total training volume has been the classical approach to accomplishing that. And if muscular size is limiting, focusing on more hypertrophy based methods with a lowered intensity and increased volume tends to work better for various reasons (easier on the joints, more time effective).
Mind you, most good strength/power athletes include both in their training anyhow. Powerlifters usually do hypertrophy work for assistance muscles after their heavier work and I have discussed how the Chinese Olympic lifting team does bodybuilding work after their low rep OL work to increase muscle size. Increased muscle size gives more strength potential while the performance of competition and assistance work trains neural factors and integrates the increased muscle size into the movements.
Not everyone does both types of training at the same time and sometimes it’s better to alternate explicit cycles of volume and intensity. First you use volume to build muscle mass and raise your strength potential before increasing neural factors to realize/maximize that potential.
The danger with this for pure strength/power athletes is losing touch with heavier weights (many find out the hard way that they rapidly lose their top-end strength) but even a low volume of heavy work maintains it pretty well. So work up to a heavyish single or triple at 80-90% and then drop back and get some volume in higher repetition ranges.
Outside of the power bodybuilding subculture who typically perform some fairly low repetition (like 5’s) work along with higher work, it’s been less common for “pure” bodybuilders (whatever that means) to do much strength work. They want a pump, not to be powerlifters or lift heavy weights. Which can be fine so long as they still focus on progression and getting stronger in those higher repetition ranges over time.
However, performing the occasional maximal strength/powerlifting type/neural cycle can pay huge dividends as I have written about before. Bodybuilders often hit a point where they simply can’t add weight in moderate repetition ranges and performing the occasional maximal strength phase where they generate more neurally focused adaptations often allows them go be able to go heavier in the higher repetition ranges: growth follows.
It shouldn’t be often or very long, perhaps one 3-6 week strength cycle every 12-18 weeks of more traditional hypertrophy training would be plenty. Since bodybuilders go nuts when they don’t get a pump, a couple of higher rep sets after the low rep work should be done.
That said, most bodybuilders couldn’t give a damn about RFD (I see training it as pointless) or relaxation or some of the other adaptations. Their training is geared towards maximizing muscle size and any specific “neural” training is aimed at aiding that. That means increasing maximal strength/neural adaptations in the muscle mass they already have which allows them to gain more muscle mass, which can then be neurally optimized.
In that vein, many powerlifters who have been on a diet of only low repetitions find that they just blow up when they move to more hypertrophy oriented training. Presumably they have such well developed neural factors that they can move big weights in moderate repetition ranges and their body can only use growth as a primary adaptation. Their joints usually thank them, too.
Other sports have their own requirements. Most need high degrees of RFD due to the fact that most sporting movements allow less than 0.2 seconds to generate force. Relaxation is critical for high speed cyclic movements like track or bike sprinting. Throwing uses a lot of SSC at the shoulder to increase force after the spin and RFD is critical (javelin throwers have the additional run-up which means high RFD and relaxation) and I think you get the idea.
And that was a way too long look at neural factors and wrap-up of this series. I really have to plan these better in the future.