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Cluster Sets for Muscle Hypertrophy: A Short Review †

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Cluster Sets for Muscle Hypertrophy: A Short Review †

Abstract and Figures

Cluster-set resistance training is focused on performance improvements of sports by increasing the repetition maximum, jump height, and efficiency in the sprint. In this commentary, we present relevant aspects to optimize the use of cluster training under the context of muscle hypertrophy. Therefore, we address intra-sets pauses, the number of repetitions per block, and strategies that benefit this methodology. During a cluster set resistance training program, not only the total number of repetitions could be higher, which means a superior total volume, but also a higher mechanical output might lead to potential benefits to muscle hypertrophy.
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OBM Integrative and Complementary
Medicine
Commentary
Cluster Sets for Muscle Hypertrophy: A Short Review
Salvador Vargas-Molina 1, 2, 3, *, Jorge L. Petro 3, 4, Diego A. Bonilla 3, 4, 5, Eneko Baz-Valle 6, Leandro
Carbone 7, Roberto Cannataro 8, Javier Benítez-Porres 1
1. Faculty of Medicine, University of Málaga, Spain; E-Mails: salvadorvargasmolina@gmail.com;
benitez@uma.es
2. EADE-University of Wales Trinity Saint David, Málaga, Spain
3. Research Division, Dynamical Business & Science Society-DBSS International SAS, Bogotá 110311,
Colombia; E-Mails: jlpetro@dbss.pro; dabonilla@dbss.pro
4. Research Group in Physical Activity, Sports and Health Sciences (GICAFS), Universidad de
Córdoba, Montería, Colombia
5. Grupo de investigación Nutral, Facultad Ciencias de la Nutrición y los Alimentos, Universidad CES,
Medellín 050021, Colombia
6. Department of Physical Education and Sport, University of the Basque Country UPV/EHU, Vitoria-
Gasteis, Spain; E-Mail: ebaz001@ikasle.ehu.eus
7. Physical Activity and Sports, Faculty of Medical Science, University of Salvador, Buenos Aires,
Argentina; E-Mail: leandrocarbone@gmail.com
8. Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, 87036 Rende,
Italy; E-Mail: r.cannataro@gmail.com
Presented at the Ibero-American Symposium in Sports and Physical Activity: Nutrition and
Training SIDANE organized by DBSS International SAS.
* Correspondence: Salvador Vargas-Molina; E-Mail: salvadorvargasmolina@gmail.com
Academic Editors: Roberto Cannataro, Jorge Luis Petro Soto and Diego A. Bonilla
Special Issue: Nutrition and Exercise for Weight Loss
OBM Integrative and Complementary Medicine
2022, volume 7, issue 1
doi:10.21926/obm.icm.2201010
Received: November 25, 2021
Accepted: March 04, 2022
Published: March 09, 2022
OBM Integrative and Complementary Medicine 2022; 7(1), doi:10.21926/obm.icm.2201010
Page 2/7
Abstract
Cluster-set resistance training is focused on performance improvements of sports by
increasing the repetition maximum, jump height, and efficiency in the sprint. In this
commentary, we present relevant aspects to optimize the use of cluster training under the
context of muscle hypertrophy. Therefore, we address intra-sets pauses, the number of
repetitions per block, and strategies that benefit this methodology. During a cluster set
resistance training program, not only the total number of repetitions could be higher, which
means a superior total volume, but also a higher mechanical output might lead to potential
benefits to muscle hypertrophy.
Keywords
Mechanical tension; intra-set; rest-pause; cluster-training; body building, body composition
1. Introduction
Traditional set (TS) schemes usually involve a specific number of repetitions, which can vary from
one onwards, performed in a continuous motion fashion without any pause in between. Moreover,
rest periods could be divided into inter-set, allocated between each set of repetitions and intra-set.
Here, the goal is to establish short recovery periods interspersed between repetitions. It is common
to see in the literature the terms cluster sets (CS), rest pause (RP), and drop sets (DS) refer to the
same concept given that all these training methodologies have the same basic structure: a set of
consecutive repetitions with a short resting period followed by more repetitions in the given set. In
DS configurations, concentric failure is desired. Once it has been achieved, immediately afterward,
the set goes on with a lower weight until muscular failure is reached. Usually, two-three weight
reductions are used, ranging between 2025% of the load, but some high-volume schemes might
involve as many weight drops as possible (REF). In contrast, RP configurations maintain the weight
while incorporating short intra-set rest periods in order to increase the volume at a given intensity,
whereas, in CS, the number of repetitions, blocks, and intra-set resting periods were fixed previously
(Figure 1). However, the standardization of the terminology and concepts used related to block
training methods is needed [1].
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Figure 1 Cluster sets, rest pause, and drop sets.
The aim of the rest period is to allow phosphocreatine (PCr) resynthesis, re-establish
intramuscular pH, enhance the clearance of cellular metabolic waste products, restore membrane
potential to resting values, and increase blood flow reperfusion into the muscle and consequently
increase oxygen transport to the tissues [2]. Previous work has shown that PCr resynthesis has a
biphasic time course behavior (fast phase during the first 2122 s and slow phase from 170 s and
beyond) during rest [3]. CS takes advantage of the fast PCr recovery kinetics and allows either a
higher mechanical output within the same training volume or a higher volume at the same
mechanical output.
2. Cluster Sets and Sports Performance
Although this short comment is focused on the potential benefits that this methodology might
have on body composition and muscle hypertrophy, it is essential to highlight that the original
objective of these advanced training methods was to increase strength and power. Moreover, most
research published on the topic reported either power or strength related outcomes such as barbell
velocity, force, and lower body power [4], sprinting and jumping capacity [58], jumping peak
velocity and height [6] and also, peak power and peak velocity [5, 9, 10]. In addition, muscular
endurance variables such as time under tension (TUT) and muscle fatigue have also been
investigated [11]. It has been well established the potential benefits of CS training methods are
increased performance-related measures such as one repetition maximum (1-RM), jumping, and
sprinting capacity.
3. Cluster Sets and Muscle Hypertrophy
As has been mentioned, even though CS protocols are more oriented to increase performance
and strength levels, they may be a useful tool to increase total volume and thus increase mechanical
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tension, which has been previously proposed as the main training stimuli behind muscle
hypertrophy [12]. While high mechanical tension is usually related only to high training loads, it can
be achieved with a wider intensity range (~60% and + 60% of 1-RM), as long as the set has reached
or is close to reaching muscular failure [13] and the load is not dropped below 30% RM [14].
Previous investigations [15] suggested that using high loads (3-RM) requires a higher number of
sets to match the effects of moderate loads (10-RM), which can be seen as a disadvantage. However,
the incorporation of a CS protocol may be the key to overcoming this issue without the need to
reach muscular failure and significantly increasing training volume. Furthermore, the effects of
different traditional sets and CS protocols on lactate concentration and velocity loss have been
reported in the set as markers of metabolic stress and performance, respectively [16]. These results
have shown that 5RM produced a similar velocity loss compared with CS but with an increased blood
lactate concentration.
The hypertrophic stimulus of a given set scheme between 6 to 20 or more repetitions is
independent of the load as long as the muscular failure is reached [17]. However, if a CS method is
applied in 35 RM blocks, with a total of 34 blocks, and intra-set rest periods are between 2030
s, TM would be high at loads approximately ~90% of 1 RM with a higher total volume.
Moreover, Oliver et al. [18] showed lesser velocity loss, higher force, and an increased total
volume in CS protocols compared with TS sets. This could be related to a greater mechanical tension.
In addition, the investigation conducted by Iglesias-Soler et al. [19] compared the maximum number
of repetitions between two protocols; the TS group performed three sets till failure with a 4 RM
load with a 3 min rest in between sets. In contrast, the CS group followed the same protocol but
with a 36-s intra-set rest period after each repetition. The total number of repetitions was more
significant in the CS group; thus, a superior total volume was achieved. Additionally, higher
mechanical performance was generated, showing a potential benefit to generate hypertrophy.
On the other hand, our team investigated three CS protocols: a) 3 RM + 3 RM + 3 RM + 3 RM with
20 s of intra-set pause; b) 3 RM + 3 RM + 3 RM + 3 RM with 40 s of intra-set pause, and c) 6 RM + 6
RM with 20 s of intra-set pause [20]. Our results indicated an increase in fat-free mass evaluated by
DXA in all protocols, although the group that worked 3 RM with 20 s of rest obtained better results.
In the same line, Gonzalez-Herndez et al. [16] showed that intra-set resting periods in between
1530 s might be better from a hypertrophy point of view, given that a similar mechanical output
could be obtained compared with more extended resting periods but with more emphasis on
metabolic stress that could enhance the muscle growth stimuli. Additionally, we report that the
application of creatine monohydrate in 3 RM protocols with 20 pauses would notably increase the
fat-free mass and strength levels evaluated by MR [21].
4. Practical Applications
Even though more research is needed, some practical recommendations for applying CS
methodology during a hypertrophy training program are depicted in Figure 2.
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Figure 2 Examples of cluster set configuration.
A. The blocks should be organized between 35 RM.
B. Intra-set resting periods should oscillate between 1020 s for the upper body or isolated
movements and between 1530 s for the lower body or compound movements.
C. Longer resting periods may be incorporated as a session progresses to avoid losses in either
total volume or concentric phase movement velocity.
D. 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 TUT. Even incorporating DS may be
a potential way of taking advantage of different cellular mechanisms behind muscular hypertrophy
and optimizing the training benefits.
E. The addition of creatine monohydrate seems to be an advantageous strategy for optimizing
the benefits of CS protocols [21].
Acknowledgments
The authors would like to thank all fellows of the Dynamical Business & Science Society DBSS
International, keynote speakers, and attendees at the Ibero-American Symposium in Sports and
Physical Activity: Nutrition and Training SIDANE that has been held in Colombia, Costa Rica, México
and Perú where this topic was fully covered.
Author Contributions
S.V. conceptualization and writingoriginal draft preparation. L.C. and D.A.B. translated the
document. J.L.P., J.B.P., E.B., R.C. and D.A.B. review and editing. All authors read and approved the
final manuscript.
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Funding
The APC was funded by the Research Division of the Dynamical Business & Science Society
DBSS International SAS.
Competing Interests
D.A.B. serves as science product manager for MTX Corporation®, a company that produces,
distributes, sells, and does research on dietary supplements (including creatine) in Europe, has acted
as a scientific consultant for MET-Rx and Healthy Sports in Colombia, and has received honoraria for
speaking about creatine at international conferences. Additionally, he serves as affiliate member of
the “Creatine in Health” scientific advisory board for Creapure® - Alzchem Group AG.
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Purpose: The purpose of this study was to determine the effects of intra-set rest frequency and training load on muscle time under tension, external work, and external mechanical power output during back squat protocols with similar changes in velocity. Methods: Twelve strength-trained men (26.0±4.2 y; 83.1±8.8 kg; 1.75±0.06 m; 1.88 ± 0.19 1RM:body mass) performed three sets of twelve back squats using three different set structures: traditional sets with 60% 1RM (TS), cluster sets of four with 75% 1RM (CS4), and cluster sets of two with 80% 1RM (CS2). Repeated measures ANOVAs were used to determine differences in peak force (PF), mean force (MF), peak velocity (PV), mean velocity (MV), peak power (PP), mean power (MP), total work (TW), total time under tension (TUT), percent mean velocity loss (%MVL), and percent peak velocity loss (%PVL) between protocols. Results: Compared to TS and CS4, CS2 resulted in greater MF, TW, and TUT in addition to less MV, PV, and MP. Similarly, CS4 resulted in greater MF, TW, and TUT in addition to less MV, PV, and MP compared to TS. There were no differences between protocols for %MVL, %PVL, PF, or PP. Conclusions: These data show that the intra-set rest provided in CS4 and CS2 allowed for greater external loads compared to TS, increasing TW and TUT, while resulting in similar PP and %VL. Therefore, cluster set structures may function as an alternative method to traditional strength- or hypertrophy-oriented training by increasing training load without increasing %VL or decreasing PP.