David Larson, B.S. CSCS
Introduction to cluster sets
The organization of repetitions, sets, and rest intervals have always been one of the defining factors involved in program design. Traditional program design structures have tended to stick to a model of using a percent 1 rep max for a set number of reps in a continuous fashion, followed by an inter-set rest period. This type of program design has certainly been shown to be effective in enhancing several markers of muscle quality (ie. hypertrophy, strength, endurance) and certainly deserves a place in exercise schedules; however, there are various ways that trainers can incorporate variety and complexity by varying the inter-rep rest, rather than just the inter-set rest. One such method to accomplish this is by utilizing cluster sets.
Cluster sets are one way to vary the inter-rep rest during a set. This allows for enhanced overall quality of the set by limiting the overall fatigue. This is very similar to the idea of interval training, as opposed to steady state endurance exercise. Cluster sets tend to see increases in movement velocity, power endurance, and power outputs when compared to traditional set structures.
There are several ways in which cluster sets can be structured; however, the most common programing methods include the standard, undulating, wave, and ascending cluster sets. There are three variables when indicating a cluster set. These include number of total repetitions, number of repetitions per cluster, and rest time between cluster. The following is an example of a loading pattern for a cluster set:
12 repetitions / 2 repetitions per cluster = 70% 1RM / 2 * 10 seconds
= 70% / 2 * 10 s *70% / 2 * 10 s … until 12 repetitions are reached.
Programming the cluster set:
There are a few things one must keep in mind when programming cluster sets. If the target goals of a training phase are strength endurance or hypertrophy, the number of repetitions per set should be higher and rest interval between reps should be lower. On the other hand, if strength and power is the goal, there should be less repetitions per set but longer rest intervals.
Undulating tend to be best for peaking due to the potentiation effect on the way down from the pyramid. Similar to undulating, the wave cluster attempts to utilize potentiation, however accomplishes it to a lesser extent. This is why it is best used during the strength or strength-power phase of a periodized training plan. The ascending cluster attempts to work the athlete into a higher intensity by slowly increase the weight and is often utilized during the peaking phase. Cluster sets can then be further varied by altering the number of repetitions contained in each cluster (ie. 10/1*10sec*10/2*10sec…).
When to use cluster sets?
Because the intention of cluster sets is to increase the quality of movement and minimize fatigue, they are usually implemented during complex power movements such as the snatch, clean, jerk, jump squats, and ballistic exercises. Furthermore, cluster sets are likely best utilized at the beginning of a workout in order to minimize the fatigue and increase set quality.
Cluster sets appear to provide a better way of maximizing power and power-endurance than traditional sets. Traditional sets, however, appear to be better suited for increasing endurance, hypertrophy, and strength. Therefore, both types of sets may be utilized in program design based on the phase and goal of training.
Haff, G. (2012). Cluster Sets: A novel method for introducing additional variation into a resistance training program. National Strength and Conditioning Association.