One of the most effective methods for developing strength is Cluster Training, a method popularized in the 70s when Carl Miller wrote about it in weightlifting magazines.
In traditional strength training the athlete is often prescribed a workout using the following loading parameters: 5 sets of 5RM, with muscular failure achieved on the last repetition of every set, and rest intervals of about four minutes. In this workout, the athlete would execute a total of 25 repetitions at 85 percent of 1RM in roughly 25 minutes of work.
With cluster training you select a higher percentage of your 1RM and rest longer between reps, for example, 10-15 seconds. Rather than performing 5 sets of 5RM at 85 percent, you might be able to use 90 percent of your 5RM. Therefore, Cluster Training would increase the total training time under higher tension for the high-threshold fast-twitch fibers, a prerequisite for reaching hypertrophy of these selected fibers.
With cluster training success in all sets and reps is critical. It is better to use a weight that is initially too light than a weight that is too heavy. Let’s say your best close-grip bench press is 300 pounds and your 3RM is 270 pounds. You could start the first cluster at the 3RM weight: 270 pounds, but it would be better to start at 255 pounds; move up if it is too easy.
A 2012 study published in the Journal of Strength and Conditioning Research tested the effects of inter repetition rest during multiple sets of the power clean. This study compared peak power output, force, and velocity in the power clean with no inter-repetition rest, or with either 20 seconds or 40 seconds of rest.
Participants were trained college-aged men, and they performed 3 sets of 6 reps of the power clean at 80 percent of the 1RM. After each rep in the “no rest” group, participants returned the barbell to the floor in a controlled manner and immediately performed the next rep. The subjects in the “rest” groups rested for 20 or 40 seconds in the start position of the power clean after they had returned the barbell to the floor.
Results showed that peak power significantly decreased by 16 percent during the “no rest” sets (i.e., there was a 16 percent drop in peak power from the 1st to the 6th rep of the set), compared to a decrease of 5.5 percent in the 20-second rest sets and to a decrease of only 3 percent in the 40-second rest sets. Peak force also decreased significantly in the “no rest” sets, whereas the other two rest groups maintained peak force throughout the set. Peak velocity of the bar also decreased significantly by 10 percent in the “no rest” group and dropped by only 3.8 percent and 1.7 percent in the 20-second and 40-second rest groups, respectively.
Previous studies support mixing up training protocols with inter-repetition rest. A study of elite Australian rugby players found that using inter-repetition rest improves lower body power and velocity when training the power clean and squat. This study indicated that cluster training can lead to greater neural adaptations and the recruitment of more Type II muscle fibers.
Finally, a 2010 study on cluster training for the upper body found that this method allowed participants to perform a high number of repetitions while maintaining the velocity of the lifting motion, even when fatigue would have become a factor in a traditional training scheme. The researchers concluded that cluster training is effective for developing power and speed for sports and should be programmed accordingly. As such, upper body cluster training can be used in sports such as wrestling, boxing, or judo, while lower body power may be enhanced for rugby, soccer or football, or for track and field throwing events.
Although commonly used for exercises that use a lot of muscle mass, such as squats, cluster training can also be used for smaller muscle groups. Here is an example of a cluster training superset that combines a large muscle group upper body exercise with a smaller one:
A1. 10-Degree Decline Close-Grip Bench Press, 3-5 clusters (5 x 1), 50X0, rest 10 seconds between reps and 120 seconds between sets
A2. Scott EZ Bar Semi-Supinated-Grip Curl,
3-5 clusters (5 x 1), 50X0, rest 10 seconds between reps and 120 seconds between sets
When you are ready to give cluster training a try, you should increase the weight only if all reps and sets are successful. When you are ready to move up, a general guideline would be to increase the weight by 1 to 3 percent.
It’s been said that the best workout program is the one you’re not using, which relates to the idea that variety is essential to achieving rapid increases in strength and power. One type of workout that should definitely be in your weight training toolbox is cluster training.