Do you want that extra edge in the gym performing workouts that no one else is doing? Or even heard of? It’s time to use the cluster set protocol.
Cluster sets are like traditional sets except they have rest periods placed within the set. For example, instead of performing one set of 5 reps, you may perform 5 reps with 20 seconds rest between each rep. The goal of the cluster set is to maintain the speed of each rep and reducing fatigue.
While using rest periods between your reps may maintain better quality reps and reduce fatigue, can cluster sets be that ace up your sleeve in strength, hypertrophy, and power development?
Table of Contents
What Are Cluster Sets?
Cluster sets are a form of varying the rest distribution within a set. A traditional set involves performing all reps in that set before resting. A cluster set can either be inter-repetition rest (rest between each rep) or intra-set rest (rest between clusters of reps) [1].
This rest between reps or clusters of reps generally ranges from 10-30 seconds [2]. However, rest can be longer than 30 seconds depending on the exercise and protocol used. These rest durations can be manipulated based on the exercises performed and the number of reps being performed in each cluster.
For example, if you are using intra-set rest and performing 2-3 reps before resting, you may use 20-30+ seconds of rest. If you are using inter-repetition rest, you may use less rest such as 10-20 seconds between reps.
But that’s not all you can play with. You can also play with the loading structure to squeeze out some pretty impressive gains in speed and power. The traditional cluster set loading structure would be using the same load throughout all of the sets.
For example, 3 x 1+1+1+1+1 at 85% 1RM. But there are two other loading structures you can use [2]. One is the pyramid set structure or the ascending set structure. The pyramid structure is similar to how a bodybuilder would pyramid their reps over multiple sets. But this is pyramiding the load within the same set.
So, if you were to perform a cluster set of 5 reps with inter-repetition rest, each rep would be with a different load. For example, 85%, 90%, 95%, 90%, 85% 1RM with 30 seconds rest between reps.
The main goal of this cluster set structure is to maximize power output on the descending portion of the pyramid through a post-activation potentiation effect meaning the work done before those reps makes the last two reps feel easier.
The ascending set structure is geared more towards strength development with a heavy dose of power. This is almost like wave loading but the wave is within the set. For example, 3 x 3 would be broken down as:
As you may have noticed, the goal of the cluster set is to allow for each rep to be performed at the highest quality possible.
By providing a short rest within the set, you can partially recover so you can give more effort to each rep. From a physiological standpoint, the use of intra-set rest allows for a reduction in blood lactate formation.
Put simply, increases in blood lactate (often associated with the “burn”) impair regeneration of energy for the working muscles [3]. Further, increases in blood lactate are associated with the increase in metabolic by-products that acidify the muscle. Mainly hydrogen ions known as H+.
While this is great for hypertrophy as you can increase metabolic stress through the build-up of these by-products, it's not great for the speed of muscle contraction. In fact, as blood lactate gets too high (along with these by-products), the ability of the muscle to contract is greatly diminished reducing the output of force and contributing to fatigue [4].
That is why employing the use of cluster sets could be your secret weapon to speed, power, and strength gains.
Benefits Of Cluster Sets
While in theory, improving the quality of each rep should enhance strength, speed, and power to a greater extent than a traditional set structure, does the evidence support this? Let’s take a look at what the literature says about the benefits of cluster sets.
Maintenance Of Rep Velocity And Power
From all of the cluster set research I have read; this is the number one benefit of the cluster set configuration. A traditional set shows a decline in rep velocity as the set progresses. A cluster set configuration attenuates this decline.
A study comparing traditional sets of bench press using 4 x 5 @85% 1RM and the same protocol with 30 seconds rest between reps (cluster sets) in resistance-trained males found the cluster set group were better at maintaining average velocity for each set [5].
We also see better maintenance of rep velocity during the squat in a 3 x 10 @10RM protocol with both 15 and 30 second rest periods between reps compared to a traditional set configuration [6]. This was not seen when using a 10 second rest period indicating that 10 seconds is too short for partial recovery.
Even breaking sets of 10 squats @70% 1RM into two clusters of 5 reps with 30 seconds between clusters has been shown to maintain higher rep velocities in the last 5 reps compared to performing all 10 reps in a row [1].
However, it seems that placing the 30-second rest every two reps instead of 4-5 attenuates the decline in set velocity to an even greater extent [7]. This resulted in greater average force, total work, and time under tension without the reduction in velocity of peak power compared with traditional sets or clusters of 4 reps [8].
When looking at Olympic Weightlifting derivatives, a cluster set configuration with the clean pull exhibited greater barbell velocities (8%) and peak power (6%) compared to the traditional set group [10].
Overall, it seems cluster sets allow you to maintain better quality reps (i.e. faster and more powerful) than traditional set structures.
Greater Possible Effective Training Volume
One study compared traditional vs. cluster sets during the back squat at individual optimal power load (load that elicits the greatest power output) [9]. The traditional set group performed 6 sets of as many reps as possible until average power dropped below 90% for two consecutive reps.
The cluster set group performed as many clusters of 2 reps with 20 seconds rest until average power dropped below 90%.
The cluster set grouped performed more reps above 90% average power and more reps in total (approximately 1.6x the number of reps) compared to the traditional set group.
So, if your goal is to perform a lot of effective volume (high power outputs for each rep), then a cluster set approach may be more beneficial during accumulation blocks.
Reduction Of Fatigue
The same study indicated that a cluster set protocol may be superior to traditional sets at reducing fatigue if the traditional set is designed to induce a large amount of fatigue. For example, sets of 10 reps or more.
This has been shown where 3 x 10 resulted in greater perceived, mechanical, and metabolic fatigue compared to cluster set structures [6].
We can also imply a greater reduction of fatigue by the better maintenance of velocity as more fatigue equals a greater loss in velocity from rep to rep.
Enhanced Peak Power And Velocity
Other than the reduction in fatigue, this is where cluster sets really shine. With ballistic movements such as jumps.
When performing 6 x 6 vertical jumps with 20% 1RM, the cluster set group who had a 30-second rest every 2 reps improved peak power by 10% and velocity by 8% after the 3-week intervention compared to the traditional set group who only improved by 3% and 2% respectively [11].
Jump velocity was maintained through the cluster set protocol while the traditional set saw a 4% decline. Interestingly, the improvement in peak power and velocity was only seen at loads of 25% body weight during the vertical jump and not 50% or 75%.
This may indicate that cluster sets with light loads transfer better to lighter loads and not to heavier loads.
Are There Any Cons To Using Cluster Sets?
So far, we’ve seen that cluster sets can be hugely beneficial to the quality of your training session. But are there any cons you should be aware of?
Increased Training Time
The main drawback of using cluster set configurations in your training is the increased training time. If you are on a tight schedule, adding 10-30+ seconds rest between your reps for each set may increase your set time by at least a minute.
While this may not seem like much. But remember that you will rarely use the 10 second rest period and most likely be using 20 seconds at the minimum over multiple sets. This adds up.
One solution around this is to use a rest redistribution set configuration. Rest redistribution has been shown to be more effective than traditional sets for maintaining rep performance and minimizing fatigue [12].
The difference between cluster sets and rest redistribution is the total time of the set.
The rest redistribution protocol simply takes your normal rest period duration of a traditional set and distributes it intra-set. Whereas cluster sets add intra-set rest on top of between set rest.
For example, if you were to perform 4 x 6 with 90 seconds rest between sets, a rest redistribution configuration could be 4 x (3 x 2) where 15 seconds is taken between rep clusters and 30 seconds is taken between sets.
You total the same number of reps, the same number of sets, but within the same time as a traditional set structure without the same fatigue.
Not As Effective For Strength Development
From my observations within the research, cluster sets do not provide a superior benefit to strength development over cluster sets when looking at long-term performance benefits. However, the main advantage of cluster sets is that they reduce fatigue both within and after the session.
This has also been the recent conclusion in a 2021 meta-analysis (the gold standard of research which combines all studies on the topic that meet specific criteria) [13]. Further, an older review has mentioned that cluster sets may be more useful for explosive power development while traditional set structures may be better for strength and hypertrophy development [2].
So, while you may be able to better maintain rep velocity and power over the set, it doesn’t seem to translate into increased strength gains more than traditional sets. For example, similar increases in 1RM bench press are seen between cluster and traditional set structures [5].
Are Cluster Sets Good For Hypertrophy?
I’ve mentioned that cluster sets may not be so good for hypertrophy as they mitigate the build-up of metabolic by-products which is one important contributor to building muscle. The original 2013 study investigating a cluster set protocol for hypertrophy found 8 x 5 between 65-75% 1RM with 60-second rest over 12 weeks induced similar muscle growth compared to traditional sets [14].
Most importantly, however, the cluster set group improved bench press and squat 1RM, power, and vertical jump power to a greater extent than the traditional set group.
Meaning they were able to get the same benefits in muscle growth with the added benefits of becoming stronger and more powerful.
Sounds like an awesome way to train to maximize gains. This study has since been replicated in 2021 where groups performed 4 x 5 @85% 1RM of the bench press either as traditional sets or with 30 seconds rest between each rep (cluster sets) over 8 weeks [15].
They saw the opposite results with the traditional group showing greater muscle growth in the pecs with similar increases in strength. The authors put this down to the greater velocity loss of the traditional set group resulting in greater fatigue and hypertrophy outcomes.
The differences between the protocols of these two studies are huge so comparing them is near impossible. But it seems if you want to use cluster sets for muscle gain, then the clusters must be performed with a higher number of reps to see this loss in rep velocity and build-up of blood lactate.
How And When Should You Use Cluster Sets?
Cluster sets are best served when you want to enhance pure power output. That could be for jumping, sprinting, or ballistic exercises such as Olympic Weightlifting. However, they can also be used in phases where you want to perform more quality volume. Here are some general guidelines for setting up your cluster set configurations:
How Many Cluster Sets Should You Do?
The number of cluster sets you perform is going to be dictated by the intensity of the exercise and the goals of the exercise. For example, if you are performing cluster sets at 90% of your 1RM, you don’t want to perform a lot of sets as you will cause a lot of fatigue.
Whereas, if you are performing hypertrophy cluster sets, this protocol uses 8 sets per exercise and multiple exercises in one session. Therefore, anywhere from 1-8 sets is likely a good range to work in with most of your exercises falling between 1-4 sets.
Myo Reps vs. Cluster Sets
Myo reps and cluster sets are often mixed up. I can see why. They both involve intra-set rest periods. However, the one distinct difference is rep quality and fatigue. Myo reps are generally done to failure or close to failure to maximize hypertrophy whereas cluster sets are never done to failure as their goal is to maximize power and velocity.
To perform a myo rep set, you’d perform reps to failure or close to it. Usually around 10-12 reps. You’d then rest approximately 20 seconds and perform micro sets of 3-5 until you reach your target rep goal.
Myo reps are essentially a form of rest-pause training made famous by the Doggcrapp training methodology.
Advanced Cluster Set Variations
Cluster sets aren’t limited to what has been presented in this article. There are other advanced methods and uses for cluster sets that have been validated within the research.
Accentuated Eccentric Loading Cluster Sets
Accentuated eccentric loading means to use a load that exceeds what you are capable of lifting upwards. This is usually anywhere from 5-30% over your 1RM.
Accentuated eccentric loading when used for all reps of a cluster set (3 x 5 @80% 1RM and 105% 1RM for the eccentric) resulted in greater eccentric work, rate of force development, and velocity compared to traditional loading [16].
Eccentric specific adaptations are next level when it comes to strength and power.
In fact, eccentric training may improve strength and power to a greater degree than traditional modalities [17].
Briefly, this is likely down to the enhancement of rate coding (how quickly your motor units can send messages to contract muscle fibers) and the ability to desensitize the Golgi Tendon Organ which is a safety mechanism that will throttle force production to protect you among many other adaptations.
Post-Activation Potentiation
I briefly touched on post-activation potentiation (known as PAP) at the beginning of this article. The phenomenon is akin to lifting a heavy bucket of water. Then, someone decides to tip half of the water out without you knowing.
You go to lift the bucket again thinking it's full so you use the same amount of force resulting in splashing yourself because you lifted it so fast. That is the basic premise of PAP. Lift something heavy. Do something light and powerful so you can take advantage of the imprint made from lifting something heavy.
Turns out cluster sets make a great initial exercise to enhance the power exercise. 3 x 2+2+2 with 20 seconds rest at individual optimal power load during the jump squat enhanced vertical jump performance at 4 and 8 minutes after the jump squats while traditional sets did not [18].
This was likely because the cluster set group was able to maintain 95% of their average power during the jumps squats whereas the traditional set group could only maintain 85% of their average power.
Safe to say, if you are lifting for a PAP effect, you likely won’t be performing 6 reps in a set due to fatigue. In my experience, you’ll usually perform up to a maximum of 4.
High-Velocity Power Training
This is a really cool cluster set variation focused on improving the ability to repeat explosive efforts. While this applies to many different team and ball sports, it can also be applicable for strength sports such as Strongman for events such as the keg toss or various overhead medleys.
High-velocity power training (or HVPT for short) is like a combined power enhancer and conditioning session in one. It has been shown to improve maximal power and the ability to repeat that power by 21-22% as well as increase anaerobic and aerobic capacity after just 6 weeks of 3 sessions per week [19].
Strength & conditioning coach Alex Natera is most well-known for applying this method within Australian Rules Football and is a great cluster set variation to try in your own training. Here are some general guidelines from Alex himself:
Here’s an example of a low volume and a high volume HVPT session:
Low Volume – 6 x 5+5+5 with 5 seconds rest between clusters and 2 minutes rest between sets. Total reps = 90.
High volume – 3 x (4 x 12) with 30 seconds rest between clusters of 12 and 1-minute rest between series. Total reps = 144.
These HVPT protocols are brutal and you must have a large training background to use them effectively.
Should You Use Cluster Sets?
The evidence is very strong in favor of cluster sets for enhancing power output and with so many different variations, you'd be silly not to at least dabble in the use of cluster sets. My advice would be to start simple. Just take whatever sets and rep you are doing now and place a 20-30 second rest between every 1-2 reps.
Monitor how you feel and go from there. If you want to get fancy, then start to experiment with some of the advanced cluster set protocols or various pyramid and ascending loading schemes.
References
1. Oliver, J. M., Kreutzer, A., Jenke, S. C., Phillips, M. D., Mitchell, J. B., & Jones, M. T. (2016). Velocity drives greater power observed during back squat using cluster sets. The Journal of Strength & Conditioning Research, 30(1), 235-243.
2. Haff, G. G., Hobbs, R. T., Haff, E. E., Sands, W. A., Pierce, K. C., & Stone, M. H. (2008). Cluster training: A novel method for introducing training program variation. Strength & Conditioning Journal, 30(1), 67-76.
3. Sahlin, K., & Ren, J. M. (1989). Relationship of contraction capacity to metabolic changes during recovery from a fatiguing contraction. Journal of Applied Physiology, 67(2), 648-654.
4. Schumacher, Y. O., & Mueller, P. (2002). The 4000-m team pursuit cycling world record: theoretical and practical aspects. Medicine & Science in Sports & Exercise, 34(6), 1029-1036.
5. Davies, T. B., Halaki, M., Orr, R., Helms, E. R., & Hackett, D. A. (2020). Changes in bench press velocity and power after 8 weeks of high-load cluster-or traditional-set structures. The Journal of Strength & Conditioning Research, 34(10), 2734-2742.
6. González-Hernández, J. M., García-Ramos, A., Castaño-Zambudio, A., Capelo-Ramírez, F., Marquez, G., Boullosa, D., & Jiménez-Reyes, P. (2020). Mechanical, metabolic, and perceptual acute responses to different set configurations in full squat. The Journal of Strength & Conditioning Research, 34(6), 1581-1590.
7. Tufano, J. J., Conlon, J. A., Nimphius, S., Brown, L. E., Seitz, L. B., Williamson, B. D., & Haff, G. G. (2016). Maintenance of velocity and power with cluster sets during high-volume back squats. International journal of sports physiology and performance, 11(7), 885-892.
8. Tufano, J. J., Conlon, J. A., Nimphius, S., Brown, L. E., Banyard, H. G., Williamson, B. D., ... & Haff, G. G. (2017). Cluster sets: permitting greater mechanical stress without decreasing relative velocity. International journal of sports physiology and performance, 12(4), 463-469.
9. Tufano, J. J., Halaj, M., Kampmiller, T., Novosad, A., & Buzgo, G. (2018). Cluster sets vs. traditional sets: Levelling out the playing field using a power-based threshold. PLoS One, 13(11), e0208035.
10. Haff, G. G., Whitley, A. D. R. I. A. N., McCoy, L. B., O'BRYANT, H. S., Kilgore, J. L., Haff, E. E., ... & Stone, M. H. (2003). Effects of different set configurations on barbell velocity and displacement during a clean pull. The Journal of Strength & Conditioning Research, 17(1), 95-103.
11. Morales-Artacho, A. J., Padial, P., García-Ramos, A., Pérez-Castilla, A., & Feriche, B. (2018). Influence of a cluster set configuration on the adaptations to short-term power training. The Journal of Strength & Conditioning Research, 32(4), 930-937.
12. Jukic, I., Ramos, A. G., Helms, E. R., McGuigan, M. R., & Tufano, J. J. (2020). Acute effects of cluster and rest redistribution set structures on mechanical, metabolic, and perceptual fatigue during and after resistance training: a systematic review and meta-analysis. Sports Medicine, 1-28.
13. Davies, T. B., Tran, D. L., Hogan, C. M., Haff, G. G., & Latella, C. (2021). Chronic effects of altering resistance training set configurations using cluster sets: a systematic review and meta-analysis. Sports Medicine, 1-30.
14. Oliver, J. M., Jagim, A. R., Sanchez, A. C., Mardock, M. A., Kelly, K. A., Meredith, H. J., ... & Kreider, R. B. (2013). Greater gains in strength and power with intraset rest intervals in hypertrophic training. The Journal of Strength & Conditioning Research, 27(11), 3116-3131.
15. Davies, T. B., Halaki, M., Orr, R., Mitchell, L., Helms, E. R., Clarke, J., & Hackett, D. A. (2021). Effect of Set-Structure on Upper-Body Muscular Hypertrophy and Performance in Recreationally-Trained Male and Female. Journal of Strength and Conditioning Research.
16. Wagle, J. P., Cunanan, A. J., Carroll, K. M., Sams, M. L., Wetmore, A., Bingham, G. E., ... & Stone, M. H. (2021). Accentuated eccentric loading and cluster set configurations in the back squat: A kinetic and kinematic analysis. The Journal of Strength & Conditioning Research, 35(2), 420-427.
17. Douglas, J., Pearson, S., Ross, A., & McGuigan, M. (2017). Chronic adaptations to eccentric training: a systematic review. Sports Medicine, 47(5), 917-941.
18. Iacono, A. D., Beato, M., & Halperin, I. (2019). The effects of cluster-set and traditional-set postactivation potentiation protocols on vertical jump performance. International journal of sports physiology and performance, 15(4), 464-469.
19. Natera, A. O., Cardinale, M., & Keogh, J. W. (2020). The effect of high volume power training on repeated high-intensity performance and the assessment of repeat power ability: A systematic review. Sports Medicine, 50(7), 1317-1339.