ACUTE RESPONSES TO CLUSTER SET TRAINING
In 2003, Haff et al. (9) examined the effect of 3 different types of set configurations consisting of a traditional set, cluster set, and an undulating cluster set. The traditional set and cluster set were performed with 5 repetitions at an intensity of 90% and 120% of 1RM power clean. The undulating sets consisted of 5 repetitions performed at an average intensity of 90% or 120% of the subject 1RM power clean. The athlete performed a repetition at 85%, 90%, 100%, 90%, and 85% of the subject's 1RM power clean for an average 5-repetition intensity of 90% or a repetition 110%, 120%, 140%, 120%, and 110% of the subject's 1RM power clean for a 5-repetition average intensity of 120%. The interrepetition rest interval for each of the cluster sets was set at 30 seconds. The 3 different set configurations were tested using the clean pull with 2 intensities of 90% and 120% of a 1RM power clean. When examining the 90% intensity trial, the cluster set exhibited a statistically significant increase in average barbell velocities (+8.1%) and a nonstatistically significant increase in barbell displacement (+5.9%) when compared to the traditional set. While the average peak power output for the set was not significantly different, the cluster set resulted in a 6.8% increase in peak power when compared to the traditional set. For the 120% of 1RM intensity, a statistically significant increase in average peak barbell velocity (+7.9%) and displacement (+2.1%) was noted during the cluster set when compared to the traditional set. Conversely, the average peak power for both the cluster sets was not different (−0.4%) than the traditional set configuration. One rationale for the lack of difference in power output during the 120% intensity cluster sets may be because previously it was reported that a 90% intensity is the optimal load for pulling exercises (8,16), thus potentially confounding the power data. Based on this study, it can be concluded that the use of a cluster set may result in enhancements in velocity of movement, displacement of the barbell, and, most likely, power-generating capacity.
In order to investigate the effects of set configurations on the acute repetition power outputs during the bench press, Lawton et al. (15) used 4 different set configurations. The 4 sets configurations included (a) a traditional set of 6 repetitions performed at a 6RM intensity with no rest between each repetition, (b) a cluster of 6 singles performed at a 6RM intensity with 20 seconds between each repetition, (c) a cluster of 6 repetitions performed as 3 pairs of doubles with a 6RM intensity and 50-second rest between each pair of doubles, and (d) a cluster of 6 repetitions performed as 2 clusters of triples with a 6RM intensity and 100-second rest between each group of triples. The first major finding of this project was that the traditional set resulted in a linear decrease in power output across the repetition range. These findings support the hypothetical model previously proposed by Haff et al. (9) (Fig. 1). Similar to the results presented by Haff et al. (9), the cluster sets resulted in statistically significant greater individual repetition power output and total power output when compared to the traditional set configuration. However, there were no significant differences between the 3 cluster set configurations with regard to individual repetition power or total power output. Lawton et al. (14) concluded that the cluster set paradigm may be very beneficial for explosive or ballistic strength exercise. Therefore, this type of set configuration may be useful to the strength and conditioning professional who is using weightlifting exercises such as the power clean, power snatch, or pulling motions.
In another investigation, Denton and Cronin (4) examined the kinematic (displacement, velocity, and acceleration), kinetic (force impulse, work, and power), and lactate responses to different set configurations. Three loading schemes were employed in conjunction with the bench press exercise in this investigation for a targeted total of 24 repetitions. The first loading scheme used was composed of 4 sets of 6 RM with a 302-second recovery between groupings (traditional = T). The second set configuration comprised 8 sets of 3 performed with a 6RM load with each group of 3 separated by 130 seconds (cluster 1 = C1). The final grouping was identical to the second with the exception that every other set was performed to volitional failure (C2). The results of the study revealed that the C2 configuration resulted in significantly greater repetitions (∼30) when compared to C1 (∼24) and the traditional (∼23.6) set configurations. When examining the mean power output, total work and impulse of the sets configurations C2 were significantly higher than both C1 and T, which were not different. The blood lactate response for C2 was consistently higher than both T and C1. The results of this investigation suggest that increasing the interrepetition rest resulted in the ability to perform more work at a higher quality.
When examining the acute studies, several key conclusions can be drawn from the literature. First, it appears that cluster set training does allow for acute alteration in the overall training stimulus induced by a specific exercise. While more work is needed in this area, it appears that these set configurations are best suited for ballistic power exercises such as those used in weightlifting or exercises such as jump squats. Finally, it appears that the cluster set configuration has the potential to increase work capacity and allow the athlete to train with a higher exercise quality as indicated by kinetic and kinematic variables. It may be hypothesized, then, that these acute responses might be magnified or manifested in long-term performance changes if these techniques are used in appropriately designed periodized training models.
LONG-TERM RESPONSES TO CLUSTER SET TRAINING
In one of the first studies on the topic, Byrd et al. (2) examined the effects of 10 weeks of resistance training with 3 different interrepetition rest intervals (zero, 1, and 2 seconds). In this study, it was determined that the 2 groups that used rest periods between repetitions were able to increase their overall work output. While the major focus of this study was directed at cardiovascular adaptations, the results are important due to the relationship between total work and training adaptations. Frobose et al. (7) suggest that the adaptive response that stimulates muscular growth is more dependent on the overall work output or volume load of the training session than the extent of the load, which appears to stimulate greater neural adaptations. Based on these findings, the implementation of the cluster set appears to allow the athlete to train with a higher intensity, thus magnifying the potential training stimulus affecting neural adaptations. Furthermore, this configuration allows fatigue aftereffects to diminish such that volume load can be increased, again, potentially magnifying adaptations.
Rooney et al. (18) also examined the effects of implementing different set configurations across a 6-week training program on isometric and dynamic markers of elbow flexor strength. Subjects were divided into 3 groups: (a) a control group that did no training, (b) a traditional set protocol, and (c) a cluster set protocol that used a 30-second interrepetition rest interval. Training was conducted 3 days per week with intensities and volumes varying between 6 sets of 6RM and 10 sets of 6RM loads. There were no differences between the cluster and traditional set protocols for maximal isometric strength. However, the traditional set configuration resulted in a significantly greater increase in dynamic muscular strength than the cluster set protocol. The results of this study suggested that during a 6-week elbow flexion protocol (18) the cluster set offered no benefit over the traditional paradigm. These results need to be examined carefully as they may be misleading in that power output was not measured. Lawton et al. (15) have suggested that cluster set training is best suited for explosive or ballistic exercises. Therefore, it is not unexpected that the elbow flexor exercise did not benefit from the cluster set protocol. Additionally, the subject population was relatively untrained, consisting of 18- to 35-year-old males and females who were only defined as being healthy. Plisk and Stone (17) in a recent review on periodization suggested the implementation of a cluster set paradigm is best suited for trained or highly trained individuals. Based on these contentions, the results of the study by Rooney et al. (18) are not unexpected, and the findings may be different if highly trained athletes were used in conjunction with explosive exercises performed in a cluster fashion.
To the authors' knowledge, the only training study that examines the effects of varying the set structure with athletes was performed by Lawton et al. (14). In this study, 12 junior basketball and 14 junior soccer players with a minimum of 6 months of resistance training experience were divided into 3 training groups. Subjects were divided into 2 training groups: (a) a traditional set group in which 4 sets of 6 repetitions performed at a 6RM intensity every 260 seconds and (b) a cluster set group of 8 × 3 performed at a 6RM intensity every 113 seconds. Subjects trained the bench press 3 days per week for 6 weeks with ~24 total repetitions for ~13 minutes and 20 seconds of exercise. At the completion of the study, the traditional set training intervention resulted in significantly greater power outputs and 6 RM strength when compared to the cluster set group. Additionally, the traditional set group resulted in a significantly greater time under tension, which was hypothesized as one of the key reasons why the traditional set produced superior results. However, the results reported by Lawton et al. (14) may have occurred as a result of the training program intervention used by the traditional group being identical to the testing protocol used to evaluate changes in muscular strength as indicated by a 6RM. This contention is supported by data presented by Izquierdo et al. (11) that suggest that when training is conducted using sets to failure, a greater improvement in tests of muscular endurance (repetitions to failure) is noted. Since Lawton et al. (14) used a 6RM, which might be considered a high-intensity muscular endurance test (25), to evaluate performance, it would be expected that the traditional set configuration would result in superior performance gains after 6 months of practicing the performance of a 6RM protocol. If other strength measures were used to assess performance gains, it is likely that different results would have occurred.
Collectively, when considering the body of knowledge about the use of cluster sets during long-term training, it appears that cluster sets allow the athlete to achieve higher power outputs and higher volume loads or work outputs. There is a paucity of long-term training intervention data looking at the effects of using the cluster paradigm with explosive or ballistic exercises. However, while the few studies currently available suggest the cluster set offers no long-term strength gain benefit, the strength and conditioning professional should consider the cluster set as a tool that may be useful in the development of specific athletic traits (9,14). This tool is probably best suited for ballistic explosive exercises and less useful for nonballistic exercises such as the bench press. Additionally, the cluster set has yet to be investigated in the context of a periodized training program. Further research is needed in order to define the most effective time points during the periodized training program in which the cluster set is most beneficial.
PRACTICAL APPLICATION OF CLUSTER SET
The implementation of cluster sets in a periodized program can be accomplished in many ways depending on the specific goals of the phase of training. For example, the goals of the hypertrophy phase of training are to stimulate hypertrophy, decrease body fat mass, and increase work capacity (23). The traditional set may actually be best suited for this phase of training for most exercises, but the goals of the hypertrophy phase of training may also be accomplished by employing shorter rest intervals, such as 15 seconds, in the cluster set. The duration of recovery between each repetition may depend on the complexity of the exercise in which the cluster set is being employed. Based on the contemporary literature, it appears that power exercises such as the power clean or power snatch might be most affected by using the cluster paradigm. For example, in weightlifting, it has been argued that performing traditional sets with the complete lifts (i.e., clean, snatches, power cleans, power snatches) using high-repetition schemes results in fatigue-induced alterations in technique that may result in the development of technical deficiencies (9,12). As a result of this belief, weightlifters generally only perform repetition schemes, which range between 1 and 5 repetitions per set (12). Conversely, the cluster set may offer a desirable solution to the volume limits that are sometimes placed on performing complete lifts as it results in increased work tolerance and can help maintain or enhance performance outcomes. Table 3 gives an example of a strength-endurance phase of training in which cluster sets could be employed for the power snatch and power clean, while traditional sets are performed with less technical exercises such as clean pulls. While the example presented in Table 3 uses 10 singles performed as a cluster of singles, one might also consider performing clusters of 2 repetitions for a total of 10 repetitions for the given set. This type of cluster orientation may actually result in greater increases in endurance as there is less recovery between each repetition.
When formulating a basic strength phase of a periodized training program, one of the primary goals is to increase muscular strength; thus, using a traditional set configuration for nonballistic exercises may be warranted. However, among advanced athletes, the force/power production during ballistic movements can be augmented using cluster sets. A shift in the interrepetition rest interval to 30 seconds is warranted as the overall intensity of the cluster should be higher in this phase of training and a greater amount of recovery may be needed between each repetition of the set. In this phase of training, the strength and conditioning professional should consider implementing an undulating cluster set configuration as it will allow the athlete to begin to use higher lifting intensities. When using the undulating cluster set, the overall intensity of the set is defined as the average kilograms lifted across the set. For example, if the athlete is to perform an undulating cluster set of 5 repetitions with an average intensity of 110 kg, the athlete might perform lifts at 105, 112.5, 117.5, 112.5, and 105 kg for each set. Table 4 presents an example of a training session in which the undulating cluster set it is used.
During a strength/power phase of a periodized training program, the primary goals are to maintain or increase muscular strength and improve power-generating capacity (23). This phase may be the logical time during a periodized program to fully use a cluster design. In this scenario, for example, the strength and conditioning coach could implement the undulating cluster set as this set configuration has a reasonable potential to produce postactivation potentiation effects. Furthermore, the use of a heavy load (mid-cluster) helps to maintain or stimulate strength gains. The use of a 30- to 45-second rest interval in conjunction with either the undulating (or ascending cluster) may be useful in allowing the athlete enough recovery between repetitions so that higher power outputs are achieved. In the ascending cluster set, the athlete would progressively increase the overall intensity of the set with each set. Thus, force output could be maximized on the final repetition. Several different variations of ascending clusters could be used. For example, the athlete may perform 3 sets of clusters consisting of 3 repetitions with the average intensity of each set being increased (set 1 = 110, 115, 120; set 2 = 115, 120, 125; set 3 = 120, 125, 130). This method potentially emphasizes peak force development and may be more suited to partial movements or power movements (e.g., power snatch) rather than full weightlifting movements due to a fatigue effect using 3 ascending sets in a row. Other configurations could be constructed potentially emphasizing different characteristics. Table 5 presents an example of a training session using an ascending cluster set.
Based on theoretical and actual scientific data, the cluster set appears to be a unique method for introducing training variation into the periodized training program. The various methods for implementing cluster sets offer the strength and conditioning professional a tool that may be useful when working with training and highly trained athletes. While more research needs to be conducted examining the performance and physiological affects of the various cluster set models, current data suggest that strength and conditioning professionals should consider using this novel training stimuli as part of their training plans, especially when working with explosive exercise such as the power clean, power snatch, and potentially pulling exercises (clean and snatch).
1. Binder-MacLeod SA, Dean JC, Ding J. Electrical stimulation factors in potentiation of human quadriceps femoris. Muscle Nerve
25: 271–279, 2002.
2. Byrd R, Centry R, Boatwright D. Effect of inter-repetition rest intervals in circuit weight training on PWC170 during arm-cranking exercise. J Sports Med Phys Fitness
28: 336–340, 1988.
3. Chiu LZ, Fry AC, Weiss LW, Schilling BK, Brown LE, Smith SL. Postactivation potentiation response in athletic and recreationally trained individuals. J Strength Cond Res
17: 671–677, 2003.
4. Denton J, Cronin JB. Kinematic, kinetic, and blood lactate profiles of continuous and intraset rest loading schemes. J Strength Cond Res
20: 528–534, 2006.
5. Fleck SJ, Kraemer WJ. Designing Resistance Training Programs
(2nd ed). Champaign, IL: Human Kinetics, 1997.
6. Folland JP, Irish CS, Roberts JC, Tarr JE, Jones DA. Fatigue is not a necessary stimulus for strength gains during resistance training
. Br J Sports Med
36: 370–373; discussion 374, 2002.
7. Frobose I, Verdonck A, Duesberg F, Mucha C. Effects of various load intensities in the framework of postoperative stationary endurance training on performance deficit of the quadriceps muscle of the thigh. Z Orthop Ihre Grenzgeb
131: 164–167, 1993.
8. Frolov VI, Efimov NM, Vanagas MP. Training weights for snatch pulls. Soviet Sports Rev
18: 58–61, 1983.
9. Haff GG, Whitley A, McCoy LB, O'Bryant HS, Kilgore JL, Haff EE, Pierce K, Stone MH. Effects of different set configurations on barbell velocity and displacement during a clean pull. J Strength Cond Res
17: 95–103, 2003.
10. Hodges, N.J., S. Hayes, R.R. Horn, and A.M. Williams. Changes in coordination, control and outcome as a result of extended practice on a novel motor skill. Ergonomics
11. Izquierdo M, Ibanez J, Gonzalez-Badillo JJ, Hakkinen K, Ratamess NA, Kraemer WJ, French DN, Eslava J, Altadill A, Asiain X, Gorostiaga EM. Differential effects of strength training leading to failure versus not to failure on hormonal responses, strength, and muscle power gains. J Appl Physiol
100: 1647–1656, 2006.
12. Jones L. USWF Senior Coach Manual
. Colorado Springs, CO: U.S. Weightlifting Federation, 1991.
13. Kraemer WJ, Fleck SJ, Evans WJ. Strength and power training: Physiological mechanisms of adaptation. Exerc Sport Sci Rev
24: 363–397, 1996.
14. Lawton T, Cronin J, Drinkwater E, Lindsell R, Pyne D. The effect of continuous repetition training and intra-set rest training on bench press strength and power. J Sports Med Phys Fitness
15. Lawton TW, Cronin JB, Lindsell RP. Effect of interrepetition rest
intervals on weight training repetition power output. J Strength Cond Res
20: 172–176, 2006.
16. Medvedev AS, Frolov VI, Lukashev AA, Kraso EA. A comparative analysis of the clean and clean pull technique with various weights. Soviet Sports Rev
18: 17–19, 1983.
17. Plisk SS, Stone MH. Periodization strategies. Strength Cond
25: 19–37, 2003.
18. Rooney KJ, Herbert RD, Balnave RJ. Fatigue contributes to the strength training stimulus. Med Sci Sports Exerc
26: 1160–1164, 1994.
19. Sahlin K, Ren JM. Relationship of contraction capacity to metabolic changes during recovery from a fatiguing contraction. J Appl Physiol
67: 648–654, 1989.
20. Sale DG. Postactivation potentiation: Role in human performance. Exerc Sport Sci Rev
30: 138–143, 2002.
21. Siff MC, Verkhoshansky YU. Supertraining
. Denver, CO: Supertraining International, 1999.
22. Stone MH, O'Bryant HO. Weight Training: A Scientific Approach
. Minnesota: Burgess, 1987.
23. Stone MH, Stone ME, Sands WA. Principles and Practice of Resistance Training
. Champaign, IL: Human Kinetics Publishers, 2007. p. 376.
24. Viitasalo JT, Komi PV. Effects of fatigue on isometric force- and relaxation-time characteristics in human muscle. Acta Physiol Scand
111: 87–95, 1981.
25. Wathen D. Load assignment. In: Essentials of Strength Training and Conditioning
. Baechle TR, ed. Champaign, IL: Human Kinetics, 1994. pp. 435–446.
26. Wootton SA, Williams C. The influence of recovery duration on repeated maximal sprints. In: Biochemistry of Exercise
. Knuttgen HG, Vogel JA, Poortmans J, eds. Champaign, IL: Human Kinetics, 1983. pp. 269–273.
Keywords:© 2008 National Strength and Conditioning Association
interrepetition rest; rest-pause; set configuration; resistance training