Firstly, allow me to apologise for my short absence! I am aware that I have not written for over 3 weeks, however on the 6th of May, little over 2 weeks ago, my son was born and I've spent every ounce of my spare time just sat staring at him in admiration! He's incredible, and both Ollie and Mum are doing amazingly well.
Now that I have settled, into having what feels like no routine, I am back and will be committing to providing you with at least one blog post each and every week.
Today's topic is all about Cluster sets: What are they, and why you should be using them.
Cluster sets have been present in strength programmes for decades. I believe that this method was first popularised in a book back in the 1970's called 'Sport of Olympic Style Weightlifting' by Carl Miller, although I am sure that it was used long before then.
In a nutshell, they are single sets that are broken down into smaller sets, separated by very short bouts of recovery, often somewhere between 10-20 seconds.
As an example, your typical strength prescription of 3 sets of 5 reps could be converted into a cluster and illustrated as follows:
3x 5 (2,2,1) - at 85% - 180 seconds recovery
In this example, you would perform 3 sets of 5 repetitions at your 5RM weight, however, the set of 5 reps is broken into 3 clusters; the first two using two reps and the third just one. Between each cluster would be a short rest period of around 10-20 seconds.
Performing 3x 5 at 85% using traditional straight sets would be arguable impossible or unrealistic at best. You couldn't expect yourself to perform 3 sets at what would be an RPE 10. Splitting the sets into clusters would make this set more like an RPE 9 and therefore more achievable for multiple sets.
3x (5x1) - at 90% - 300 seconds recovery
In this example, you would perform 3 sets of 5 repetitions at your 4RM weight, however, the set of 5 reps is broken into 5 clusters of 1 repetition with a short rest period of around 10-20 seconds per rep.
Performing 3x 5 at 90% using traditional straight sets would normally be impossible. You cannot perform 5 reps at your 4RM weight. Splitting the sets into clusters would make this set more like an RPE 9-10 and therefore more achievable, whilst placing a greater stimulus on your nervous system.
Clusters can be used for a variety of reasons, whether that be for improving technique, increasing strength or even gaining muscular size, however, in today's post we're going to focus on using clusters for improving force production: an extremely valuable ability, essential for almost all sports and disciplines.
Why do they work?
During straight sets, fatigue increases as you near the end of a set, or at least it should if you're lifting loads that are appropriately challenging. This results in the speed of the bar decreasing and therefore the amount of force being produced to decrease.
You are not going to produce as much force on the 5th rep as you are on your first.
This isn't so useful, particularly if we want to get extremely explosive, as improvements in Rate of Force Development (RFD) are dependant on your ability to produce more force at faster rates. This is achieved either by lifting heavier loads at the same velocity, or moving the same loads faster.
Yes, grinding out the last rep on as PB attempt is useful, after all a slow, heavy, ugly rep is what demonstrates strength and helps illustrate our level of work and effort towards improving performance, however, that doesn't mean that grinding out reps is the most efficient way of getting strong.
This is where clusters come in.
Clusters have the effect of reducing the amount of fatigue that accumulates over a single straight set by incorporating short rest periods between a series of reps in that set. Although this may have a negative effect on the rate of muscle growth, this method seems to have a positive effect on the rate at which high-velocity strength and power are improved.
This may be because of the faster bar speeds that are used in training throughout the entire set.
Cluster sets therefore represent a valuable training tool for athletes who need to improve high-velocity strength for sport.
What does the recent science say?
Whether cluster sets cause different gains in maximum strength from traditional sets is relatively unknown as it has not been very well-explored. The research does look extremely promising, however previous studies have used the same weight in both training groups and control groups, which defeats the point of using cluster sets for increasing maximum strength, as they enable the use of heavier loads for the same number of reps.
In relatively modern research, both maximum strength and force in jump squats tend to increase more using traditional set and therefore straight sets should not be ignored and avoided.
A very recent study this year explained how cluster sets allowed greater gains in velocity and power output specifically when using light loads - in this case, they used 6x (3x2) Jump Squats at 20% 1RM.
This load is light enough to be a genuinely “ballistic” or explosive exercise, so performance is dictated by the factors that determine explosive force production. These include:
Increased early phase activation because of an increase in motor unit firing frequency
Velocity-specific reductions in antagonist coactivation
Increases in single fiber contractile velocity that may not relate to changes in fiber type as measured by myosin heavy chain isoform, and a greater maintenance of type IIX fiber type.
The change in early phase activation caused by an increase in motor unit firing rates is thought to be the most important factor.
Even over a very short phase of power training during this study lasting just 3 weeks, a cluster set configuration produced greater increases in bar speed and power output in jump squat tests using loads (25% of 1RM) that were close to the load used in training (20% of 1RM), perhaps because greater speeds can be used with intra-set rest periods.
Athletes who need high-velocity strength for sporting movements, such as vertical jumping, sprint running, and changing direction, may benefit from performing power training with intra-set rest periods, in a cluster format, and focusing on moving the bar as quickly as possible.
Info-graphic taken from S&C Research Review and derived from Tufano, Brown & Haff (2017)
Whether or not cluster sets are optimal for improving maximal strength is a little unclear. The evidence looks promising however no studies are yet to use practical loading strategies.
Recent research, however, has shown how clusters can be extremely effective at improving velocity and force production, which is essential for individuals who take part in sports such as Weightlifting, Boxing, Tennis, Track & Field and other sports that involve vertical jumping, sprinting, and changing direction.
Next time you are attempting such movements in the gym, try breaking your sets down into smaller clusters using short intra-set rest periods to allow for maximum lasting bar velocity.
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Tufano, J. J., Brown, L. E. & Haff, G. G., 2017. Theoretical and Practical Aspects of Different Cluster Set Structures: A systematic Review. The Journal of Strength & Conditioning Research, 31(3), 848-867.
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