Cluster sets help to maintain speed

Muscle adaptations require a combination of neural stimulation and muscle fiber stimulation. Explosive training is critical to developing the power release capacity that builds strength. When you train with heavy weights, the speed of the movement decreases with increasing repetitions. For example, if you perform a set with your maximum weight for 10 repetitions, the speed of movement will drop significantly between the third and tenth repetition. The stores of the high-energy energy source adenosine triphosphate (ATP) and creatine phosphate are rapidly depleted, contributing to fatigue and reduced training speed.

Cluster sets - where short breaks are taken during the set - are a good technique for maintaining training speed throughout the set. For example, if you perform four sets of 10 repetitions, the sequence of the cluster would look like this: five repetitions, 30 seconds rest, five repetitions, 90 seconds rest, five repetitions, 30 seconds rest, five repetitions, 90 seconds rest, etc.

Jonathan Oliver of Texas Christian University found that training speed and time under tension were higher when using the cluster technique for squats than for traditional sets. The quality of the sets is higher when using the cluster technique because the pause intervals promote the resynthesis of high-energy ATP and creatine phosphate.

(Journal Strength Conditioning Research, 30: 234 - 342, 2016)