Use Cluster Sets to Gain Muscle Mass

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Personal Fitness Trainers Wolverine Lake Michigan

There are a ton of mass gaining workouts out there, but one overlooked method is the use of a cluster set. A cluster set will add some intensity to the workout, meaning that you’ll get a nice blend of strength to go along with that size.

What’s a cluster set you ask? It’s simply breaking up a set into more manageable chunks. Take a set of 12 reps – a tried and tested method to add some muscle mass. By your 6th rep, bar speed will start to slow and the last 2-3 reps are going to be a grind. So if you’re lifting 100 pounds you’re literally only putting 100 pounds of force into the bar by the last repetition (otherwise you’d lift the weight a thirteenth time).  Besides just reps, bar speed is a vital component to adding some muscle.

A cluster set will take that set of 12 and break it into 4 sets of 3 reps.  Because we’re dividing the reps up, we can go a touch heavier. So instead of 100 pounds, let’s use 115. So your set now looks like this:

Do 3 reps, rest 15 seconds, Do 3 reps, rest 15 seconds, 3 reps, rest 15 seconds, Do 3 reps.

Out of the gate, you’re lifting more weight for 12 reps, which gives you a big gold star for the day. But if we dig a little deeper, force production will be a little higher as well. What I mean by this is taking the 15 seconds of rest allows your high threshold motor units (the muscle cells most responsible for size and strength) to recoup a little bit and stay in the game (1). These muscle cells allow you to put more “oomph” into the bar. The more force you apply to the bar, the more muscle you’ll develop. Remember that set of 12 reps? You’re getting weaker and weaker with each rep and cluster sets lets you avoid getting weak.

Researchers put cluster sets to the test. Using junior level basketball players and the bench press, researchers discovered that breaking up the set allowed the players to nearly double their power output (from 25 to 49%) over subjects who did straight sets (2)! More power equals more potential for muscle growth.

For those interested in just size gains, I would focus on doing 3-5 reps per set with 15 seconds of rest between the clusters.

However, if you want get stronger as well, you’ll want to do 2-3 reps per set with 20 seconds of rest. Here’s how each would look:

Pure Size Gains:

  1. 45 Degree Incline DB Pronated Press – 4 x 4/4/4, 4-0-1-0, rest 15 sec/60 sec

Size and Strength Gains:

  1. Paused Front Squat – 5 x 2/2/2/2, 3-2-1-0, rest 20 sec/90 sec

If you’re bored of the same old routine, then give clusters a try and enjoy the mass gain!

  1. Baker, Daniel. Newton, Robert U. “Methods to Increase the Effectiveness of Maximal Power Training for the Upper Body.” (2005) Strength and Conditioning Journal 27;6. 24-32
  2. Lawton, T.W., Cronin, JB., Lindsell, R.P. “Effect of Interrepetition Rest Intervals on Weight Training Repetition Power Output.”(2006) Journal of Strength and Conditioning Research. 20.1. 172-176


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