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Blast Your Legs with Cluster Training

Take a standing eight count in the middle of your heaviest leg-training sets — doubling the reps you can do with a heavy weight — to build strength and spur significant new growth.

When a well-timed blow floors a boxer, the fight isn’t always over. More often than not, he’ll come to his senses, stagger to his feet, and steady himself for another bout of punishment. And depending on the organization governing the fight, he’ll often get a 10-second grace period or a standing eight count, giving him just enough time to compose himself and come back swinging.

Okay, so maybe you’ve never gone toe to toe with 12-ounce gloves on. But if you’ve stood with a loaded barbell on your back and squatted below parallel for rep after rep until you couldn’t force yourself back up out of the hole, you know what it’s like to withstand a Tyson-like pummeling. 

What you may have also noticed — particularly if you’ve experimented with the rest-pause intensity technique, in which you take a very short break during your set only to continue right back on — is that even though a heavy set of squats can leave your legs as shaky as those of a clock-cleaned prizefighter, your ability to lift heavy returns fairly quickly. In fact, after just a few seconds of rest, you’re often able to continue a set well past the initial point of failure. 

And while rest-pause is a great way to take advantage of this restored potential, a similar method, called cluster training, lets you embark on a significantly heavier set from the first rep and extend it into rep ranges that would normally be out of your reach to maximize your neural response and encourage greater growth. The trick is simply a matter of timing.

Extend Your Set

Cluster training is simply using nontraditional sets-and-reps schemes that contain built-in pauses,” says Bret Contreras, MS, CSCS, who trains both bodybuilders and strength athletes in Scottsdale, Arizona. The idea, of course, is to lift a heavier weight — about 85% of your 1RM — for more reps than you normally would when following a typical hypertrophy (muscle building) routine. 

Whereas a standard rep count for hypertrophy tends to fall between 8–12 reps per set with a weight that forces failure somewhere within that range, cluster training lets you use a heavier weight (typically one that you’d be able to lift for no more than five reps) and pushes each set into a hypertrophy rep range (meaning, you’re doing 8–12 reps with a weight that’s so heavy you’d normally fail at just five). In short, you’re doing more reps — far more — with a heavy weight to place significantly more stress on your target muscles.

 The concept of cluster training is fairly straightforward, but the sheer number of available cluster variations — from antagonistic clusters to Mike Mentzer’s cluster method — could easily sway some bodybuilders from incorporating them into their routines. So to focus your energy on lifting heavy instead of wasting time deciphering obscure training science, we’re going to stick with one cluster method in particular that we find especially promising. It’s a variation called Extended 5s, developed by Quebec bodybuilder and strength coach Christian Thibaudeau.

The goal behind an Extended 5s cluster is to perform a set of 10 reps with a weight that you could normally lift for only five reps. The method is similar to rest-pause, an intensity technique in which a lifter completes a set and then, after a very brief rest, continues to perform reps until he reaches failure a second and third time, extending the set beyond his usual point of failure to more effectively tax the target muscle group and encourage growth.

 The main difference between cluster training and rest-pause, however, is that rest-pause is often used at the end of a standard set performed with a moderate weight (e.g., a set of 5–6 reps using a lifter’s 8–10RM) and the initial rest period is undertaken without going to muscle failure. Cluster training has pauses built in throughout the set, allowing you to use significantly heavier weights, which ensures that you’ll reach muscle failure on each one.

The science behind cluster training isn’t anecdotal; in fact it relies on the body’s normal physiological response of swiftly restoring adenosine triphosphate (ATP), a molecule that the body uses to transport energy within cells. ATP is essential to every activity you undertake, but it plays an especially prominent role in heavy, short bursts of resistance training, where it combines with creatine phosphate to provide short-term energy for high-intensity work. The beauty of cluster training, as with rest-pause, is that the built-in 7–12-second rest provides just enough time for you to restore enough ATP to continue on with your heavy set, effectively increasing both the intensity and the volume of your workout.

By the Numbers

A typical set in Extended 5s cluster training would go as follows:

• Load the bar with your 5RM (that’s a weight in which you can perform only five reps, typically about 85% of your 1RM) and do five reps. 

• Rack the bar and rest for no more than 7–12 seconds (if you have one, have your spotter play referee and count out loud, but you can do it as well). 

• Immediately get back under the bar and do another 2–3 reps. 

• Rack and repeat the 7–12-second rest. 

• Complete a final 2–3 reps to finish the cluster set. When finished, you’ll have done 10 reps (and hit the exact center of the typical hypertrophy rep range) with a weight that you could usually lift for only five reps. From there, rest for 3–5 minutes before starting your next cluster set.

In Your Workout

Now that you understand the basic mechanics behind cluster training, let’s consider how it fits into your leg-day routine. As Contreras points out, “All leg exercises can be clustered, but since you’re aiming for neural adaptations it makes sense to use heavy compound movements rather than lighter isolation movements.” 

For that reason, your cluster training will revolve around the front and back barbell squat, one of the best lower-body mass builders (in addition to the deadlift). Because you’ll have to quickly rack and unrack the bar to take full advantage of your brief rest periods, be sure you’re set up to do so — whether you’re training in a basic squat rack, power cage or Smith machine, and be sure your partner is on deck to help you.

Contreras also insists that individuals should “always do clusters first in a workout, right after a general dynamic warm-up and a specific warm-up on the exercise at hand.” The reasoning here is simple: You’ll be able to lift the most weight and create a maximal neural response while you’re still fresh. And it should come as no surprise that your 5RM on the squat will be significantly less after you’ve performed other multijoint or isolation exercises than it would if you did squats at the beginning of your routine.

You also shouldn’t be applying clusters to more than one exercise. “Clusters should be reserved for just one movement per workout,” Contreras says. “Then you can add exercises that focus more on metabolic stress and cellular swelling”, otherwise known as hypertrophy-focused single-joint movements. For these accessory lifts, listed under “Cluster Combos”, you’ll follow basic sets-and-reps schemes with standard breaks of about two minutes between sets. 

* This article has been condensed for the site. The original version appears in issue 346 of MuscleMag.