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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
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:;
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:;
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:
7. Physical Activity and Sports, Faculty of Medical Science, University of Salvador, Buenos Aires,
Argentina; E-Mail:
8. Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, 87036 Rende,
Italy; E-Mail:
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:
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
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
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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.
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].
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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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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The loss of muscle mass and strength in elderly population (especially after the age of 65–70) represents a public health problem. Due to the high prevalence of frailty in older adults, cardiovascular or low-intensity exercise is implemented as first choice option. Although beneficial these training schemes are not as effective as strength-based resistance training for increasing muscle strength and hypertrophy. In fact, when performed progressively and under professional supervision, strength-based training has been proposed as an important and valid methodology to reduce sarcopenia-related problems. In this mini-review, we not only summarize the benefits of weight resistance training but also highlight practical recommendations and other non-conventional methods (e.g., suspension training) as part of an integral anti-sarcopenia strategy. Future directions including cluster set configurations and high-speed resistance training are also outlined.
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Creatine monohydrate (CrM) supplementation has been shown to improve body composition and muscle strength when combined with resistance training (RT); however, no study has evaluated the combination of this nutritional strategy with cluster-set resistance training (CS-RT). The purpose of this pilot study was to evaluate the effects of CrM supplementation during a high-protein diet and a CS-RT program on lower-limb fat-free mass (LL-FFM) and muscular strength. Twenty-three resistance-trained men (>2 years of training experience, 26.6 ± 8.1 years, 176.3 ± 6.8 cm, 75.6 ± 8.9 kg) participated in this study. Subjects were randomly allocated to a CS-RT+CrM (n = 8), a CS-RT (n = 8), or a control group (n = 7). The CS-RT+CrM group followed a CrM supplementation protocol with 0.1 g·kg−1·day−1 over eight weeks. Two sessions per week of lower-limb CS-RT were performed. LL-FFM corrected for fat-free adipose tissue (dual-energy X-ray absorptiometry) and muscle strength (back squat 1 repetition maximum (SQ-1RM) and countermovement jump (CMJ)) were measured pre- and post-intervention. Significant improvements were found in whole-body fat mass, fat percentage, LL-fat mass, LL-FFM, and SQ-1RM in the CS-RT+CrM and CS-RT groups; however, larger effect sizes were obtained in the CS-RT+CrM group regarding whole body FFM (0.64 versus 0.16), lower-limb FFM (0.62 versus 0.18), and SQ-1RM (1.23 versus 0.75) when compared to the CS-RT group. CMJ showed a significant improvement in the CS-RT+CrM group with no significant changes in CS-RT or control groups. No significant differences were found between groups. Eight weeks of CrM supplementation plus a high-protein diet during a CS-RT program has a higher clinical meaningfulness on lower-limb body composition and strength-related variables in trained males than CS-RT alone. Further research might study the potential health and therapeutic effects of this nutrition and exercise strategy.
Full-text available
bstract: BACKGROUND: Cluster Training (CL) is an alternative to traditional training where intra-set breaks are incorporated. Positive effects have been reported on sports performance. However, there is little research on body composition in trained subjects. OBJECTIVE: The aim of this study was to investigate the effects of three cluster training (CL) protocols comprised of different intra-set rest (RIntra) and blocks of repetitions (BK) on strength, power and body composition in individuals maintaining a high protein diet. METHODS: Twenty-nine resistance-trained male participants were randomized to RIntra 20 s and BK 3 RM (n= 8, CL1), RIntra 40 s and BK 3 RM (n= 7, CL2), RIntra 20 s and BK 6 RM (n= 7, CL3), and control group (n= 7, CG). All participants performed two sessions per week of lower-limb resistance training for 8 weeks. RESULTS: There were significant changes in FFM in CL1 (0.9 ± 0.5 kg, P= 0.001, ES = 0.17), CL2 (0.6 ± 0.5 kg, P= 0.010, ES = 0.14) and CL3 (0.6 ± 0.4 kg, P= 0.011, ES = 0.14) but not in CG (0.4 ± 1.1 kg, P= 0.323, ES = 0.13). Likewise, significant increases were found in the cluster groups (CL1, 14.5 ± 12.3, P= 0.012, ES = 0.80; CL2, 10.1 ± 4.3, P= 0.001, ES = 0.60; CL3, 9.5 ± 4.9, P= 0.002, ES = 0.45) but not in CG (9.0 ± 9.0, P= 0.057, ES = 0.55). There were no significant changes for any group in CMJ. CONCLUSIONS: We conclude that a RIntra of ∼ 20 s in CL protocols with 3 RM blocks in multi-joint exercises of the lower-limb is sufficient to elicit significant training adaptations; no additional benefits were obtained using longer rest intervals.
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Baz-Valle, E, Fontes-Villalba, M, and Santos-Concejero, J. Total number of sets as a training volume quantification method for muscle hypertrophy: A systematic review. J Strength Cond Res XX(X): 000-000, 2018-This review aimed to determine whether assessing the total number of sets is a valid method to quantify training volume in the context of hypertrophy training. A literature search on 2 databases (PubMed and Scopus) was conducted on May 18, 2018. After analyzing 2,585 resultant articles, studies were included if they met the following criteria: (a) studies were randomized controlled trials, (b) studies compared the total number of sets, repetition range, or training frequency, (c) interventions lasted at least 6 weeks, (d) subjects had a minimum of 1 year of resistance training experience, (e) subjects' age ranged from 18 to 35 years, (f) studies reported morphologic changes through direct or indirect assessment methods, (g) studies involved participants with no known medical conditions, and (h) studies were published in peer-reviewed journals. Fourteen studies met the inclusion criteria. According to the results of this review, the total number of sets to failure, or near to, seems to be an adequate method to quantify training volume when the repetition range lies between 6 and 20+ if all the other variables are kept constant. This approach requires further development to assess whether specific numbers of sets are key to inducing optimal muscle gains.
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The purpose of this paper was to conduct a systematic review of the current body of literature and a meta-analysis to compare changes in strength and hypertrophy between low- versus high-load resistance training protocols. Searches of PubMed/MEDLINE, Cochrane Library and Scopus were conducted for studies that met the following criteria: 1) an experimental trial involving both low- (≤60% 1 RM) and high- (>60% 1 RM) load training; 2) with all sets in the training protocols being performed to momentary muscular failure; 3) at least one method of estimating changes in muscle mass and/or dynamic, isometric or isokinetic strength was used; 4) the training protocol lasted for a minimum of 6 weeks; 5) the study involved participants with no known medical conditions or injuries impairing training capacity. A total of 21 studies were ultimately included for analysis. Gains in 1RM strength were significantly greater in favor of high- versus low-load training, while no significant differences were found for isometric strength between conditions. Changes in measures of muscle hypertrophy were similar between conditions. The findings indicate that maximal strength benefits are obtained from the use of heavy loads while muscle hypertrophy can be equally achieved across a spectrum of loading ranges.
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This study aimed to compare mechanical, metabolic, and perceptual responses between two traditional (TR) and four cluster (CL) set configurations. In a counterbalanced randomized order, 11 men were tested with the following protocols in separate sessions (sets × repetitions [inter-repetition rest]): TR1: 3×10 [0-s]; TR2: 6×5 [0-s]; CL1: 3×10 [10-s]; CL2: 3×10 [15-s]; CL3: 3×10 [30-s]); CL4: 1×30 [15-s]). The exercise (full-squat), number of repetitions (30), inter-set rest (5 min), and resistance applied (10RM) was the same for all set configurations. Mechanical fatigue was quantified by measuring the mean propulsive velocity during each repetition, and the change in countermovement jump height observed after each set and after the whole training session. Metabolic and perceptual fatigue were assessed via the blood lactate concentration and the OMNI perceived exertion scale measured after each training set, respectively. The mechanical, metabolic, and perceptual measures of fatigue were always significantly higher for the TR1 set configuration. The two set configurations that most minimized the mechanical measures of fatigue were CL2 and CL3. Perceived fatigue did not differ between the TR2, CL1, CL2 and CL3 set configurations. The lowest lactate concentration was observed in the CL3 set configuration. Therefore, both the CL2 and CL3 set configurations can be recommended because they maximize mechanical performance. However, the CL2 set configuration presents two main advantages with respect to CL3: (1) it reduces training session duration, and (2) it promotes higher metabolic stress, which to some extent may be beneficial for inducing muscle strength and hypertrophy gains.
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Morales-Artacho, AJ, Padial, P, García-Ramos, A, Pérez-Castilla, A, and Feriche, B. Influence of a cluster set configuration on the adaptations to short-term power training. J Strength Cond Res 32(4): 930-937, 2018-This study investigated the effects of a traditional (TT) vs. cluster (CT) resistance training on the lower-body force, velocity, and power output. Nineteen males were allocated to a CT or a TT group and took part of a 3-week resistance training (2 weekly sessions). CT involved 6 sets of 3 × 2 repetitions (30 seconds rest every 2 repetitions and 4 minutes 30 seconds between sets). TT comprised 6 sets of 6 continuous repetitions (5 minutes rest between sets). Before and after the training period, force (F25, F50, F75), velocity (V25, V50, V75), and power (P25, P50, P75) were obtained during the countermovement jump (CMJ) exercise at 3 external loading conditions (25, 50, and 75% of body mass). Individual linear regressions were used to determine the force-velocity profile including the Slope, estimated maximal theoretical force (F0), velocity (V0), and power (P0). After CT, very-likely moderate increments in P25 were observed compared with TT (p = 0.011, ES = 0.55) because of a very-likely moderate rise in V25 (p = 0.001, ES = 0.71). No significant differences were observed in any of the F-v profile variables between the TT and CT groups (p ≥ 0.207, ES ≤ 0.31). Our results suggest that 3 weeks of muscle power training including cluster set configurations are more efficient at inducing velocity and power adaptations specific to the training load.
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The purpose of this study was to compare the kinematic, metabolic, endocrine, and perceptual responses of three back squat protocols with equal loads, number of repetitions, and total rest duration. Eight strength-trained men performed 36 back squats using 75% 1RM and 420 s of total rest during basic cluster sets of 4 (CS4), rest-redistribution sets of 4 (RR4), and rest-redistribution sets of 1 (RR1). Ratings of perceived exertion (RPE), blood lactate (La), mean velocity maintenance (MVM), and mean velocity loss (MVL) were measured during exercise. Total testosterone (TT), growth hormone (GH), cortisol (C), and sex-hormone binding globulin (SHBG) were measured before exercise and 15, 30, and 60 min post-exercise. There were no differences between protocols for MVM. However, MVL was less during RR1 compared to RR4 (p=0.032), and neither protocol was different than CS4. All protocols resulted in similar increases in RPE and La, which remained elevated up to 30 min post-exercise (p<0.05). In all protocols, GH increased and returned to baseline by 60 min post-exercise (p<0.05). At 60 min post-exercise, TT was less than all other time points (p<0.05). There were no main effects for time for SHBG or C. The data from this study show that different types of cluster set protocols can result in pro-anabolic physiological responses to resistance training. Additionally, coaches can redistribute rest periods without affecting perceived effort or metabolic and hormonal changes if the external load, number of repetitions, and total rest time are equalized.
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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.