Olympic weightlifters often use cluster training for developing maximal strength and power. Cluster sets involve intermittent rest periods (~30 seconds) between repetitions. For example, a set of 6 repetitions can be performed in a cluster configuration by performing repetitions 1 and 2, rest for 30 seconds, performing repetitions 3 and 4, rest for 30 seconds, then finish the remaining 2 repetitions. In contrast, a traditional straight set would involve performing all 6 repetitions with no rest periods. The cluster configuration is thought to lead to superior improvements in power adaptations by enabling a higher power output for each repetition, even towards the end of the set. With a traditional straight set, power tends to progressively decline as fatigue accumulates and ATP-PC stores diminish. Thus, cluster sets may be useful for athletes when the aim is to develop maximal power.
A new study published ahead of print in the Journal of Strength and Conditioning Research compared the effects of a traditional set versus cluster set training intervention for enhancing lower body power output. A group of 19 college-aged males were randomly divided into a traditional set group (6 sets of 6 reps with 20% of 1RM) and a cluster set group (6 sets of 6 reps with 30 seconds rest between every 2 reps with 20% of 1RM) featuring the barbell jump-squat. Both groups trained twice per week for three consecutive weeks. Preceding the power training intervention, both groups performed an 8-week periodized training program progressing from weeks of circuit training to hypertrophy training and finishing with strength training. Before and after the intervention, velocity outputs during squat jumps with 25%, 50% and 75% of 1RM were quantified via force plate.
The results showed that the cluster training group experienced a significant increase in jump-squat velocity at 25% 1RM. This increase was significantly greater than that observed in the traditional set group (effect size = moderate). Apart from this, no other significant differences were observed for jump-squat velocity at 50% and 75% of 1RM. These results are likely due to the fact that the power training phase exclusively involved loads at 20% of 1RM. Therefore, the adaptations were specific to the imposed training demands. This considered, it appears that cluster training is superior to traditional straight set training for improving velocity at a specific load. Therefore, coaches should consider prescribing cluster configurations during power development phases.
Morales-Artacho, AJ. Influence Of A Cluster Set Configuration On The Adaptations To Short-Term Power Training. Journal of Strength and Conditioning Research, In Press.