Written by Garett Reid | NSCA, CSCS, CISSN, M.S.E.S.S
Fact checked by Tyler DiGiovanni, BSBM
FACT CHECKED
Compound sets, super sets, drop sets, pyramid sets, and classic straight sets…just a few different set variations you can use when performing your exercises.
They all aim to build bigger, stronger muscles, but the research behind them can vary depending on the specific style.
Well, there's a new special set in town now, the cluster set, and it might just be the best of them all.
What's awesome about cluster sets is that you can adjust the way you use them to optimize various training goals.
More importantly, there is plenty of research to demonstrate its effectiveness, so much so that you'll probably be convinced you should be using it in your program.
What Are Cluster Sets?
Cluster sets use a special set protocol designed to optimize muscle mass and strength gains while mitigating fatigue.
The most basic structure of a cluster set is to divide a single set into smaller "cluster sets" of a few reps with brief rest periods in between.
From there, the specific protocol can vary greatly depending on your specific needs. But here's how it might look. Let's say you're supposed to do the bench press with 200 lbs for 6 reps. Using cluster sets may look like this;
- 2 Reps
- Rest 20 seconds
- 2 Reps
- Rest 20 seconds
- 2 Reps
You could also do this with 2 cluster sets of 3 reps or even 6 cluster sets of 1 rep.
In addition, the rest time can vary as well. With that said, the total number of cluster sets is 2-5, with each consisting of 2-4 repetitions and separated by short rest intervals of 10-30 seconds.
After finishing one full set, you would rest as normal until you do your next set, whether 30 seconds or 2 minutes.
Another option could be to just perform one large cluster set. Let's pretend you want to perform the bench press using a 3X6 rep scheme. In total, this would equate to 18 reps. Therefore, you could use 6 cluster sets of 3 reps or 9 cluster sets of 2 reps.
While slightly different, another similar method similar to cluster sets is what are called "rest-pause" sets.
Rest-pause sets were created by Nautilus exercise machine inventor Arthur Jones, then subsequently made famous by Mike Mentzer and his high-intensity training (HIT).
To perform rest-pause sets, you start by performing your first traditional set to failure. You then rest 15-30 seconds followed by another mini-set to failure which you then repeat for a total of 2-4 mini-sets.
Studies have shown that both cluster sets and rest-pause can improve adaptations, but neither tends to be better than the other.¹
Regardless, this method enables lifters to maintain better form and technique, handle heavier loads, and achieve greater muscle fatigue and hypertrophy due to increased time under tension.
How Do Cluster Sets Work?
When performing a traditional set of successive repetitions, fatigue gradually sets in until a lifter can no longer perform more reps. It's important to understand that fatigue isn't necessarily a bad thing, as it actually stimulates the neuromuscular system and also plays a role in muscle growth.
However, being able to do more work until fatigue sets in is superior for several reasons.
The first is that less fatigue means the ability to lift more volume, which ultimately means more muscle growth.
In addition, mitigating fatigue can allow a lifter to lift more weight, theoretically resulting in more strength gains. Further, by mitigating fatigue, a lifter can perform reps with better form while producing higher power output.
Yet another benefit of cluster sets comes from the intermittent rest between repetitions within a set, which can alleviate fatigue. This allows an athlete to maintain consistent performance throughout the exercise session.
One of the primary mechanisms that produces fatigue is the inability to produce enough ATP, the molecule responsible for supplying energy to muscle contractions. Therefore, the small rest intervals performed during cluster sets allow the body to produce more ATP.
Think about it as being able to stop to refill your car so you don't run out of gas on a road trip.
Research To Back Up Their Benefits
So, the theory behind cluster sets seems to support their use. But how do they work in actual lifting sessions?
Well, they work. Numerous studies have shown that when compared with traditional sets, cluster sets produce benefits through various mechanisms.
For example, a 2017 study used three different set configurations for back squats. For all three, the total number of reps was 12.
To do this, one traditional set used 60% of 1RM for the full 12 reps. One group used 3 cluster sets of 4 reps with 75% 1RM, and another performed 6 cluster sets of 2 reps using 80% 1RM.
At the end of the program, the cluster sets saw greater total work and time under tension. At the same time, the cluster groups had no greater loss in velocity speed or peak power, suggesting similar amounts of fatigue even with the larger loads. This suggests they allowed more work at the same level of effort.²
More importantly, it showed us that using cluster sets would allow more total volume, which, when used over time, would likely result in greater muscle growth. You could also choose to use heavier loads, which would theoretically result in increased strength gains over time.
Another study from 2013 made similar revelations. In this study, groups of athletes perform squats using heavy loads of 4RM. Again, the cluster set group allowed more reps, yet the athletes could sustain higher mechanical performance levels.³
The recurring result seen in all studies on cluster sets is fatigue reduction. You can then use this lack of fatigue to your advantage: perform more reps, lift more weight, practice form, or finish your set with lower RPE.
Evidence for the mitigation of fatigue is so strong that researchers suggest more research be done with the elderly, special populations, and rehab patients!⁴
How To Utilize Cluster Sets In Your Training?
The one caveat for using cluster sets is that they are usually performed with larger barbell movements, such as the barbell back squat, bench press, deadlifts, etc.
No rule says you couldn't use these with bicep curls and skull crushers, but something like drop sets or even the rest-pause strategy we discussed earlier would most likely be a better alternative for those.
That said, you could use cluster sets to optimize the variable you're trying to achieve based on your goals. You basically use the same traditional variables and then apply them to the cluster sets.
For Power
If you're interested in increasing power, one option stands out. Use cluster sets of just 1-2 reps and longer intraset rest periods (think 2 minutes between full sets, NOT clusters).
This will allow you to perform reps with maximal power output while maintaining good form. Pair this with longer rest breaks of 20-30 seconds between clusters to allow the body to rest before each rep.
For Strength
If you're trying to increase strength, your primary goal is to get more weight on the bar. This extra load should be accompanied by less fatigue build-up and lower RPE.
For example, instead of performing bench press with a 3X5 rep scheme using 200 lbs, you could perform bench press with 3 sets of (2, 2, 1) or 3 sets of (1, 1, 1, 1, 1) using 205 lbs.
For Muscle Growth
If muscle growth is your primary goal, increasing volume is your primary objective in your sessions, as this is the number one variable that drives muscle growth.
The best way to do this is to increase the total number of repetitions. You could simply use the same load but perform more reps to do this.
For example, let's pretend you're doing a bentover row. You might use a traditional set of 150 lbs using a 3X8 rep scheme. You could do 3 sets of 9 reps or 10 reps using cluster sets. You could do this by doing 3, 3, 3 or 3, 3, 2, 2.
Cluster Sets Can Optimize Your Training
Those were just 3 examples of how you could possibly use cluster sets in your training, but there are many more. As more research is done, we'll likely discover more ways cluster sets could optimize our training.
Again, there is no specific protocol to cluster sets which is the beauty behind their use. There's also no complicated formulas to follow nor must you swap around weight plates. All you do is give yourself a little rest every few reps and you do more work of higher quality.
This simplicity, paired with their effectiveness, is what makes them such a powerful tool to have in your arsenal!
Related: How to Use Supersets, Tri-Sets, Giant Sets & Compound Sets
References
- Latella, Christopher, et al. “The Acute Neuromuscular Responses to Cluster Set Resistance Training: A Systematic Review and Meta-Analysis.” Sports Medicine, vol. 49, no. 12, 11 Sept. 2019, pp. 1861–1877, https://doi.org/10.1007/s40279-019-01172-z.
- Tufano, James J., et al. “Cluster Sets: Permitting Greater Mechanical Stress without Decreasing Relative Velocity.” International Journal of Sports Physiology and Performance, vol. 12, no. 4, Apr. 2017, pp. 463–469, https://doi.org/10.1123/ijspp.2015-0738.
- Iglesias-Soler, Eliseo, et al. “Performance of Maximum Number of Repetitions with Cluster-Set Configuration.” International Journal of Sports Physiology and Performance, vol. 9, no. 4, July 2014, pp. 637–642, https://doi.org/10.1123/ijspp.2013-0246.
- Latella, Christopher, et al. “Strengthening the Case for Cluster Set Resistance Training in Aged and Clinical Settings: Emerging Evidence, Proposed Benefits and Suggestions.” Sports Medicine, vol. 51, no. 7, 13 May 2021, pp. 1335–1351, https://doi.org/10.1007/s40279-021-01455-4.
Garett Reid
Author