A cluster set is a set that includes intermittent rest between repetitions or groups – “clusters” of repetitions. By taking a 10–30 second rest in between repetitions, you can delay fatigue and keep intensity high during a training session.
By utilizing cluster sets, you can increase your training volume and the amount of intense work you can cram into a workout. More reps with a higher weight means higher intensity throughout the workout, and possibly greater results in the form of strength and power output.
The immediate anabolic effects of cluster sets are, until now, unexplored. The magic words here are “muscle protein synthesis”. Do cluster sets stimulate muscle protein synthesis as well as traditional sets do? A new study might have the answer.
Young, resistance-trained men with a personal 1RM best of 150±9.1 kg in the barbell squat participated in the study. In a series of randomized, crossover trials they performed 2 different bouts of squat training.
The first bout consisted of 4 cluster sets with 2×5 repetitions per set and 30 seconds of intra-set rest and 90 seconds of rest in between cluster sets. The second bout consisted of 4 traditional sets with 10 repetitions per set and 120 seconds of rest in between sets. Since this was a crossover study, all participants performed both bouts, but in randomized order, on different occasions.
The barbell was loaded with 70% of the participants 1RM with the volume load equated between conditions.
The researchers measured muscle protein synthesis and anabolic signaling through phenylalanine infusions, blood samples and muscle biopsies at rest, immediately following the training sessions, and 2 and 5 hours afterwards.
The results showed no differences between traditional resistance training and cluster sets. Muscle protein synthesis and anabolic signaling (phosphorylation of p70S6K and 4EBP1 in layman terms) were the same.
In other words, if you like to use cluster sets as part of your workouts, you don’t have to lie awake at night worrying about your muscle growth. You will stimulate it just as effectively as with straight-forward, traditional sets.