What are cluster sets and can they improve muscle growth?

Posted by Dayne Hudson in Muscle Building

Estimated reading time: 7mins

Cluster sets for muscle growth

The new review outlines how cluster sets fit into your everyday workout routine.

Take a look at the below or click here:

  • Traditional Sets (TS)
    1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
    - 12 repetitions -
  • Drop Sets (DS)
    1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, Descent Rest, 12, 13, Descent Rest, 14, 15
    - 12 repetitions + descent load + 2 repetitions + descent load + 2 repetitions -
  • Rest Pause (RP)
    1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, rest, 12, 13, 14, 15
    - 12 repetitions + rest + 4 repetitions... -
  • Cluster Sets (CS)
    1, 2, 3, 4, rest, 5, 6, 7, 8, rest, 9, 10, 11, 12
    - 12 repetitions = 4 repetitions + rest + 4 repetitions + rest + 4 repetitions -

    from Vargas Molina et al 2022 - Example of cluster sets, rest pause, and drop sets.

Traditional sets are simply 12 reps straight, drop sets are doing 12 reps, then reducing the load, doing more reps, and reducing the load again. The rest-pause involves doing 12 reps, resting, then doing 4 reps.

Then we get to our star of the show: the cluster sets

As you can see, they involve doing 4 reps, resting, then doing another 4 reps, resting, and then another 4 reps.

That's how a cluster set makes up 12 reps, as opposed to our "traditional" sets of just doing 12 reps in succession.

Women lifting weights

But how long should we rest in between our cluster sets?

The review outlined how three different rest periods were analysed in a previous study:

  1. 3 Rep Max (RM) + 3 RM + 3 RM + 3 RM with 20 s of intra-set pause
  2. 3 RM + 3 RM + 3 RM + 3 RM with 40 s of intra-set pause
  3. 6 RM + 6 RM with 20 s of intra-set pause

Group number 1, the 3 rep max with 20 seconds of rest, got the best muscle growth results.

A previous study also found that rest periods of 15-30 seconds between cluster sets "might be better from a hypertrophy point of view."

The authors also point to a very recent study that found creatine monohydrate to notably increase the fat-free mass and strength levels during cluster sets! So make sure you’re taking some creatine when you’re doing cluster sets! 

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Cluster sets are so favourable because you're working at such high intensity during every rep.

Research shows they lead to lesser velocity loss, higher force and more volume compared to traditional sets.

The authors suggest this might be because of mechanical tension, which is one of the three principles of muscle growth (as I outlined in this article).

And in this squatting study, subjects either did:

Traditional sets: (4 rep max load) 3 sets of reps to failure, with 3 minutes rest in between.

Cluster sets: 36 seconds of rest between each rep.

So what did they find?

The cluster set group was able to pump out more reps! This meant they achieved more volume.

Also, mechanical performance was generated, showing a potential benefit to generating better muscle growth. 

As researchers put it in the review:

"Cluster sets takes advantage of the fast phosphocreatine recovery kinetics and allows either a higher mechanical output within the same training volume or a higher volume at the same mechanical output."

Will Rogers lifting heavy weights

So what are some other ways we can use cluster sets?

This is what the researchers recommend click here:

  • Cluster Sets (CS)
    1, 2, 3, rest 15s, 4, 5, 6, rest 20s, 7, 8, 9, rest 30s, 10, 11, 12
    - 12 repetitions = 3 repetitions + rest 15sec + 3 repetitions + rest 20sec + 3 repetitions + rest 30sec + 3 repetitions -
    Progressive increase of the intra-sets pause (from rest 15 to rest 30)
  • Cluster Sets (CS)
    1, 2, rest 20s, 3, 4, 5, rest 15s, 6, 7, 8, 9, 10, rest 15s, 11, 12, 13, 14, 15 Failure
    - 15 repetitions = 2 repetitions + rest 20sec + 3 repetitions + rest 20sec + 5 repetitions + rest 20sec + 5 repetitions -
    High Mechanical Tension (From 1 to 5), More Metabolic Accumulation and more EMG (from rest 15sec to Failure)
  • Cluster Sets (CS) + Drop Sets (DS)
    1, 2, rest 20s, 3, 4, 5, rest 12s, 6, 7, 8, Descent Rest 15sec, 9, 10... Failure, Descent Rest 15sec, 11, 12... Failure
    - 2 reps + rest 20sec + 3reps + rest 20sec + Descent load + Reps until failure + Descent load + Reps until failure -
    High Mechanical Tension (From 1 to 8), More Metabolic Accumulation and more EMG (from Descent load + Reps until failure)

    from Vargas Molina et al 2022 - Examples of cluster set configuration.

You can see how rest periods and reps performed in between can vary. So pull this image up next time you're in the gym and want a new challenge!

The authors add these practical applications for us:

  • Cluster set blocks should be organized between 3–5 reps.
  • Intra-set resting periods should oscillate between 10–20 s for the upper body or isolated movements and between 15–30 s for the lower body or compound movements.
  • Longer resting periods may be incorporated as a session progresses to avoid losses in either total volume or concentric phase movement velocity.
  • The use of mixed blocks, where the initial ones have a more mechanical tension orientation and the last ones with emphasis on metabolic stress with longer time under tension. Even incorporating drop sets may be a potential way of taking advantage of different cellular mechanisms behind muscular hypertrophy and optimizing the training benefits.
  • The addition of creatine monohydrate seems to be an advantageous strategy for optimizing the benefits of cluster set protocols.

The bottom line on cluster sets

Is that cluster sets are a great way to induce potentially more muscle growth via mechanical tension, one of the three principles of muscle growth. Cluster sets also allow for more volume to be completed. You can complete a cluster set by doing 3-5 reps, then resting 10-20 seconds for the upper body, or 15-30 seconds for the lower body, before performing your reps again. Complete this between 3-4 blocks. Adding creatine monohydrate might be beneficial on the days you're performing this. You can also incorporate drop sets within-cluster sets. All of this helps to overload the muscles in a way they might not be used to, which could translate into more muscle growth.

References:

  1. Vargas Molina, Salvador & Petro, Jorge & Bonilla, Diego & Baz-Valle, Eneko & Carbone, Leandro & Cannataro, Roberto & Benítez-Porres, Javier. (2022). Cluster Sets for Muscle Hypertrophy: A Short Review †. OBM Integrative and Complementary Medicine. 7. 1-7. 10.21926/obm.icm.2201010.
  2. González-Hernández JM, García-Ramos A, Castaño-Zambudio A, Capelo-Ramírez F, Marquez G, Boullosa D, Jiménez-Reyes P. Mechanical, Metabolic, and Perceptual Acute Responses to Different Set Configurations in Full Squat. J Strength Cond Res. 2020 Jun;34(6):1581-1590. doi: 10.1519/JSC.0000000000002117. PMID: 28700515.
  3. Bonilla DA, Kreider RB, Petro JL, Romance R, García-Sillero M, Benítez-Porres J, Vargas-Molina S. Creatine Enhances the Effects of Cluster-Set Resistance Training on Lower-Limb Body Composition and Strength in Resistance-Trained Men: A Pilot Study. Nutrients. 2021 Jul 4;13(7):2303. doi: 10.3390/nu13072303. PMID: 34371813; PMCID: PMC8308441.
  4. Oliver JM, Kreutzer A, Jenke SC, Phillips MD, Mitchell JB, Jones MT. Velocity Drives Greater Power Observed During Back Squat Using Cluster Sets. J Strength Cond Res. 2016 Jan;30(1):235-43. doi: 10.1519/JSC.0000000000001023. PMID: 26121432.
  5. Iglesias-Soler E, Carballeira E, Sánchez-Otero T, Mayo X, Fernández-del-Olmo M. Performance of maximum number of repetitions with cluster-set configuration. Int J Sports Physiol Perform. 2014 Jul;9(4):637-42. doi: 10.1123/ijspp.2013-0246. Epub 2013 Oct 23. PMID: 24154989.

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