THE ULTIMATE GUIDE TO CLUSTER SET TRAINING...
COULD CLUSTER SETS BE THE SHARPEST TOOL IN YOUR TRAINING TOOL BOX?
Cluster sets feature really high on my list of effective training methods that work for a lot of components of athletic development. For some reason though, cluster sets training is typically seen as an advanced training methodology (at least among the best training methodologies that are out there). However I don’t really agree with this viewpoint – cluster sets can (& should) really be for everyone.
If you have happened to hear me discuss training approaches or seen any of my content in the past, you will know that when it comes to optimal training programs I heavily promote clusters for everyone. Perhaps the perspective of an advanced training method is due to the confusion surrounding what cluster sets are and how they are applied (for example this has popularity as a method to promote hypertrophy and muscle building which isn’t always viewed as . Maybe this is seen as an advanced training methodology because of the fact that people are used to reading traditional sets and reps schemes? (or that most training softwares makes it difficult to program clusters, because of the rigidity of traditional sets and reps schemes).
Whatever the reason, in this post the aim is to discuss the most effective approaches to programming cluster sets in your training program to optimize your training goals. We will show you how cluster sets training really is for everybody and not an advanced training method… and even make the case as the most effective programming methods in your training tool box.
WHAT IS A CLUSTER SET?
Firstly let’s start with a quick overview of what a cluster set is…
This is a training method that divides a traditional set scheme into smaller subsets of reps, or “clusters,” separated by brief rest intervals. This rest (known as intra-set rest) serves as a little period of time between each of the “clusters” with the aim to maximize the athletes output throughout the whole set.
This is unlike a traditional set where the athlete continues to perform repetitions until the desired rep count is met. The traditional set format usually results in accumulation of fatigue across the set (e.g. things start to slow down the further your get into the set and reps become a little more grindy for high rep ranges).
Example of cluster set formats that can be created for a 12 repetition set.
Generally speaking the cluster set training method allows athletes to perform the given repetitions with a higher quality output. We generally see that you’re able maintain your velocity at higher speeds during each repetition (potentially suggesting greater rate of force development across a whole set compared to traditional sets). From my own research you can most likely lift the same equated load for more volume, when using cluster sets compared to traditional set structures.
The figure above compares the mean velocity of the back squat for cluster sets (4 reps + 20 secs rest) compared to that of traditional set in which 12 reps was volitional failure.
What we can see from the above is that velocity is maintained for the equivalent rep number throughout the cluster set. Whereas with the traditional set method the velocity decreases as the rep number increases. This is a practical example of how cluster sets can maintain your output throughout a set.
SO HOW DO I PROGRAM CLUSTER SETS ?
We have established what a cluster set is and quickly shown how cluster sets can be used to optimize your effective reps within a set. But you are probably wondering how you should program cluster sets?
I typically use the cluster set methodology for the main exercise(s) in my training program (i.e the ones training the biggest muscle groups, which induce the largest hormonal responses to training). However that doesn’t mean this principle can’t be applied to other exercises in your program too.
One of the first primary utilities I see for using cluster sets in a training program is to drive a greater amount of volume at a given intensity (i.e. perform more reps of the load than you would compared to a traditional set / reps scheme). This is why it’s perfect for your primary lifts (in which typically the key focus is load progression and force development).
As we can see from the above videos and example, not only do we maintain our speed and output across the rep range, but also the cluster set of 4 reps also allows for more total repetitions to be performed per set. I must admit I probably could’ve ground out 1-2 more reps on the traditional and at least 1 more complete cluster. Either way you get the picture clusters allow you to do more with more.
CLUSTER SETS FOR HYPERTROPHY...
I have previously posted on why this also makes it a good candidate for muscle growth and driving hypertrophy type adaptations within a training program: Hypertrophy Clusters, big hype or big hypertrophy?
Partly this is due to the total volume load (reps x load) and total strain that is achieved through the cluster set method. The ability to push your cluster sets closer to failure (which is shown to be one of the essential factors for muscle growth) with a greater rate of force development is also a nice additional benefit of training with cluster sets.
When it comes to hypertrophy we are generally trying to accumulate more volume per set through the use of a cluster scheme, but also create enough fatigue to get us flirting with at or near failure. Which is what makes it a solid method for hypertrophy training. Therefore I feel cluster set rep ranges should take us into the numbers that are traditionally seen as hypertrophy rep ranges (i.e. >10 reps). Yes I know we can get hypertrophy with less reps, but this is where clusters combines the two principles. We can do a 4 + 4 + 4 cluster of a higher intensity than what we could ever do a 1 x 12 equivalent straight set.
CLUSTER SETS VOLUMES ARE NOT JUST FOR HYPERTROPHY...
Another benefit of accumulating more volume while dissipating fatigue can be within the dimension of athlete training.
For example during the pre-season period for athletes training we want to ramp up and improve their floor on all athletic qualities so they are ready for competition. But S&C is often in conflict with increased sport practice volumes etc.. which place additional demands on the athlete. Ultimately we want to get after it, but also not overcook the training and overtrain.
So how can we get additional volumes of resistance training in? You guessed it, cluster sets!
There is evidence to suggest that cluster sets reduce the perceived effort from training and also show a decrease in cortisol post training (suggesting a lowered fatigue response when compared to traditional sets).
Given these additional benefits this also makes clusters a viable option for in-season training. My caveat here is the goal is likelyt o keep the total volume load lower (which may give us the opportunity to keep intensity high throughout the in-season period). My thoughts are to manipulate the intensity based on the training week while manipulating the volume when you need to truly deload.
Lastly in the off-season (when we aren’t too worried about sport competition). This method can really be used to push the athletes ceiling. Within my training programming this is where a shift in focus happens with the primary goal being maximal dynamic strength and improving max efforts. Which I will explore in more detail below:
CLUSTER SETS FOR MAXIMAL STRENGTH ?
There are a number of other complimentary adaptations we have already discussed (i.e. power and hypertrophy) which come in conjunction with cluster set training. So what else is there? Well this would be improving strength.
For maximal strength we likely don’t necessarily need to flirt with failure in the sense of high amounts of volume. A lot of max strength training typically occurs in the <5 repetition ranges. But what we do want to improve is the repeatability of these higher intensity muscle actions (e.g. the ability to sustain performance closer to the athletes maximum dynamic force ceiling). This is why I typically keep my cluster sets under 3 reps for maximal strength (with a view that the cluster set will likely be terminated <9 reps).
I have also used a special type of cluster set training in the past (the 20 x 1 method; which uses inter-repetition rest performing heavy singles). I have also seen examples of this method such as 10 x 1 etc. In any case, this method works for squeezing that little more out of your heavy strength work too, by performing heavy singles, with a little less rest than what you would do normally (I have used this method all the way up to 95% of 1 repetition max.
Of course I would be naive to suggest that you can’t get all of the above adaptations at once and there is no one perfect set rep scheme that is purely going to isolate one adaptation (though potentially you’re training with a higher overall load for strength vs power, and with higher volumes for hypertrophy). So here is my general thoughts on how to structure clusters in a session to potentially get all 3 adaptations (strength, power and hypertrophy in one bout).
The cluster based warm up is a fantastic means to get exposure to those lighter loads (when warming up) but switching the mindset to intent and activation. This is the area where you can get your power work in without even realizing it. I generally program 3-4 reps in the cluster warm up and depending on the main working sets I will typically do at least 5 warm up sets.
The main bulk of the session can then be directed to the primary goals of force production (whether than is rate of force, or peak force efforts adding greater intensities). The last option is a means to tack on a little bit more volume through either extending you rep ranges or using drop sets to distribute another exposure on the load-velocity continuum). I have found the drop set method to be particularly useful here as can again move with a lighter load (which exposes us to a greater speed component and slightly higher than the warm up).
WAYS TO DETERMINE AN OPTIMAL CLUSTER SET ?
In the past I have used a couple of different ways to program cluster sets. What is the optimal cluster is going to depend on the resources you have available. It is also going to be very different within individuals based on their training age, strength level and the exercise being used. Here we cover the 3 main ways to program cluster sets optimally:
THE VELOCITY BASED TRAINING APPROACH TO CLUSTER SETS...
For those that have access to a velocity based training (VBT) tool a simple means to establish a cluster set is using the velocity feedback to guide your decision making process. With the additional measure of velocity you can begin to determine the “drop point” (i.e. the point in which velocity starts to decrease). This is a good starting point to begin to determine an “optimal” cluster. So how do you go about this
Have an athlete perform a set of failure at a relative intensity then apply specific thresholds to either the first or best rep (e.g. 5% / 10% / 20 % drops)
Note the number of reps accumulated before these thresholds are met. In the example above our 5% threshold would be around 3 reps. This would be the threshold I would use for this exercise to keep a person most fresh through the set (e.g. in-season training block).
The 10% threshold is around 4-5 reps. This would be the one where we want to flirt with fatigue a little bit but still accumulate some volumes (e.g. pre-season training).
Lastly the 20% threshold is 8 reps. It’s likely this just becomes more akin to a traditional set range. But what this does tell me is that for this given load 8 seems to be the limit where things fall off. Therefore we can use the above approaches e.g. 2+2+2+2 or 4+4 to determine our cluster set ranges. Or use a modified cluster in which the person performs 8 reps, rests and then performs a handful more reps (in the case of this AMRAP they got to 12) so this could be an 8 + 4 format to get them to near their set failure point.
But what if you dont have a VBT device?
THE RESEARCH BASED TRAINING PROGRAM CLUSTER SET...
There have been numerous studies to date that have detailed cluster set training and I won’t cover them all but here are some of the set – rep schemes I have found most useful:
THE LOW TECH SUBSTITUTE TO DETERMINE CLUSTER SETS...
This becomes a little more tricky (in which case you can use the default cluster formats above). However if you do want to create an individual cluster format, then you can use perception as a guiding principle.
- Do you get to a point where the reps start to feel more grindy?
- Or a particular point in which perceived effort increases?
Simply make a note of the number of reps and then begin to play around with different formats. Adding and subtracting reps where you can.
As a general rule of thumb a cluster set should likely have at least 1 rep left in the tank (rep in reserve) until the final cluster is performed (e.g. if you are pushing the volume to maximal capacity). But this is also depending on what rest format you use.
HOW DO I DETERMINE THE REST BETWEEN CLUSTER SETS?
As we begin to round off this post I often get asked this question… What is the best rest time for a cluster sets?
From our understanding of the scientific research applied to training and rest schemes, there are potential different adaptation responses stimulated by different formats of rests in traditional sets (e.g. longer rest periods help mitigate fatigue). However in the cluster set research there is no general consensus on rest schemes. Though a recent study showed greater power output the longer you rest (e.g. 15 secs vs 45 secs; Ryan et al, 2024). Though it should be noted that this was on the fly wheel which likely exhibits a higher proportional load (and potentially fatigue) compared to other types of training.
In my opinion for it to be considered a true cluster set you need to keep the rest time below 45 seconds. Unless you’re attempting a high volume of clustered reps with an intensity of >85% your 1 repetition max or doing the 20 x 1 method. But in general the sweet spot seems to be about 30-45 secs.
Times longer than 45-60 seconds just feel a lot like a traditional split set method (which is really just a longer rest period than that given intra-set with the clusters format). I might be flexible with 45 seconds to 1-minute on really high intensities 85% 1-RM and above or when the goal is truly optimizing RFD with the highest weight we have. Longer rest periods than this would be in line with the low rep high set methods (which is fine but it’s not a cluster).
The main point here is that I prefer just giving the smallest amount of rest that can be used to still maintain the athletes output within the rep scheme, whilst also not dissipating all the fatigue that is being created at the same time. It’s the trade off between maximizing both metabolic and mechanical strain
SO WHY ARE CLUSTER SETS THE MOST EFFECTIVE TRAINING METHOD?
To date I haven’t seen a research paper that has displayed a negative effect of the cluster set training method, nor does it display adaptations inferior to other methods. So we know this method works and has an evidence base to support it. It is also a method that can help with things like in-season training where traditional approaches may be less appropriate or less well received.
Though I should note a couple of researchers have suggested this method to take longer session duration than traditional training methods. But my one rebuttal here is this is also related to the protocols and rest periods that are being used (a lot of the time 60 secs – is this really a cluster?).
"THE ARGUMENT AGAINST" CLUSTER SET TRAINING...
enerally this is when cluster sets are being taken beyond traditional set rep ranges, which I normally program for hypertrophy purposes (so not with everyone all the time). I think this is fine and you likely accrue more effective working volume in the cluster set (so can potentially even take a set or 2 off with clusters and still get a very good training stimulus). Given that this would get us to our effective number of reps completed for the day, likely faster or just at the same time as traditional sets, practically I dont think timing is ever an issue.
Now another contrary argument against cluster set training is often that you can gain the same adaptations from traditional set reps schemes. The problem I have here is that a lot of research performs volume-load matched studies. One thing we know about training is the muscle doesn’t really care how it gets the load, so when it is matched we are likely going to see similar hormonal responses due to the strain imposed (and so similar adaptations).
What a lot of these studies fail to do is recognize the inherent major positive of cluster sets (you can do more reps with the same given load in comparison to traditional set reps schemes). So ultimately we can likely drive greater volumes of work, at faster speeds, which sounds awfully like a great recipe for enhancing your performance and adaptations.
THE MAIN REASON CLUSTERS SHOULD BE IN YOUR PROGRAM...
Lastly, my favorite reason is that it can be used with literally anyone!
- Beginner to training use clusters to learn movement patterns the little rest periods provide a great opportunity to coach / be coached and review your form.
- Older adult clients; Similar to the beginner older adult clients are likely to fatigue faster in traditional set reps schemes. Clusters allows them to maintain their set rep volume, just like everyone else.
For example this study by Rappelt & Colleagues demonstrated lower overall percieved effort with similar changes in maximal voluntary contractions (improvement in strength in the elderly populations with two different cluster set strategies). This would make it a solid candidate for the above mentioned populations. But this effect also has some desirable qualities for others (as we have described before).=
- Athlete, whether its in-season, off-season or pre-season a cluster format can easily be imposed into the program.
- Advanced lifter – its likely you haven’t used this method before if you are an advanced lifter, therefore this creates a novel stimulus.
In my opinion everybody should be using cluster sets. If you’re a coach you’re missing out by not programming this method. If you are an athlete you should be thinking about adding these to your program. With so many upsides with very little (if any) downside, this might be one the most effective methods you can have in your tool box for maximizing your training in the weightroom.
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