When you first begin training, traditional resistance training is enough to make gains in strength and hypertrophy, but over time you have to find different ways to challenge your muscles. The way to do this is by tweaking variables such as the resistance you use, the number of repetitions you do, the number of sets you complete, total training volume, exercise order and rest period between sets. Unless you change these variables at intervals, your muscles will no longer have a new stimulus to adapt to, and you’ll stop gaining strength and muscle mass.
One type of training that challenges your muscles differently is called cluster training. Cluster training is a variation on traditional resistance training that helps you maximize the amount of resistance you use and the number of reps. With cluster training, you break up a standard set into “clusters” by inserting short rest periods into the set at intervals. For example, instead of doing a full set of 8 repetitions without pausing, you might add 20 second rest periods after every 2 repetitions that you do. If you do 3 sets total using the cluster technique, you would write it down on paper as:
3 X (2+2+2) 20 sec. rest intraset
This simply says you’re doing 3 sets in clusters of 2, 2, 2 with 20 seconds rest between each cluster.
Why bother breaking up a set with rest periods? The goal is to increase the amount of weight you can lift and the number of repetitions you do. When you do a set of reps with no intraset rest periods, your muscles fatigue towards the end of the set as lactic acid and other metabolic by-products build-up and pH drops. The onset of fatigue limits the number of reps you can do.
When you introduce strategic pauses or rest periods, your muscles have an opportunity to partially recover from fatigue before you do the next rep. This should allow you to perform more reps for each set. Most proponents of cluster training recommend intraset rest periods of between 10 and 30 seconds. Another bonus: Introducing intraset rest periods will allow you to increase the amount of resistance you can use.
In addition, introducing rest periods maximizes the velocity or explosiveness with which you can lift, which is why cluster training is so effective for power training. Cluster training taps into the power of a phenomenon called post-activation potentiation. PAP, or post-activation potentiation, is the ability of muscles to contract with more force after a previous muscle contraction. For example, if you do a set of squats prior to doing an explosive exercise like squat jumps, your performance for the squat jumps will be better. Your nervous system has essentially “psyched up” your muscles to contract with greater force when you did the set of squats. The key is that the squats not cause muscle fatigue. If the muscles are fatigued, no potentiation occurs. By introducing rest periods so that your muscles don’t completely fatigue, you can produce a more forceful contraction on the reps that follow while still enjoying the benefit of being able to do more total reps.
Benefits of Cluster Training for Strength and Hypertrophy
You can use cluster training as a way to enhance strength, hypertrophy or power by varying the resistance you use, the number of reps in each cluster, the length of the intraset rest periods and how many sets you do. Manipulating these components will help you fine-tune your workout to best achieve your goals.
If your goal is to develop strength, choose a weight that’s 85 to 90% of your one-rep max. You might do a single rep, or at most 2 reps, followed by a 10 to 20-second rest. Repeat each cluster 5 times with 10 to 20 seconds of rep between each. Because you’re using a heavy load, you’re maximizing strength development and the rest period between the reps will maximize the total number of reps you can do.
When you’re training for hypertrophy, unlike strength, you want more fatigue and lactic acid build-up and more time under tension to create enough metabolic stress to stimulate muscle growth. So, increase the number of reps you do before introducing a rest period. You can also use heavier resistance than you normally would since you’re introducing rest periods into the set.
For example, you might choose a resistance that’s 80 to 85% of your one-rep and do 12 to 15 reps with 30 second rest periods within the set. A method described by Verkhoshansky recommends starting with 8 reps, resting 30 seconds, and then gradually decreasing the number of reps you do before introducing another 30-second rest. For example, 8 – rest – 3 – rest – 2 – rest – 1 – rest and then a final rep. Expect this to be challenging! By introducing rest periods into a hypertrophy set, you’re able to complete more total reps, thereby increasing the total time the muscle is under tension. When doing multiple sets, give yourself a 3 minute rest period between sets.
Does Cluster Training Really Improve Performance?
Sounds good, but does it work? A study published in the International Journal of Sports Physiology and Performance supports the idea that cluster training boosts performance. In this study, 9 judo athletes did squats using a resistance comparable to their 4 rep max, corresponding to the maximum weight at which they could do 4 repetitions. In one workout they did as many reps as they could in a traditional manner, completing 3 total sets with 3 minutes rest between sets. In a subsequent workout, they did as many squats reps as possible, only they did it cluster style, introducing intraset rest periods The results? When they used the cluster method, the athletes were able to complete a greater number of reps, and they were able to generate more velocity with each repetition.
The Bottom Line
Cluster training is a way to introduce variety into your workout as well as increase training density. It’s a challenging workout, but one that can help you break out of a plateau and add an element of novelty to your workouts. If you’re looking for a way to “shake things up,” give cluster training a try.
Muscle and Fitness. “Cluster Set Training for Strength and Size”
Elite FTS. “Cluster Training”
Int J Sports Phys Ther. 2011 Sep; 6(3): 234-240.
International Journal of Sports Physiology and Performance. (2013). Performance of Maximum Number of Repetitions With Cluster Set Configuration.
NASE website. “Traditional Versus Cluster Set Training for Strength and Power”
Strength and Conditioning Journal, 30 (1), p.67-76.
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