Let’s talk about cheat reps and muscle growth

Various factors related to exercise technique have become hot topics in the evidence-based fitness space. A narrative review published in 2024 seemed to suggest we don’t know as much as we think about how technique impacts hypertrophy.

In this review, the authors concluded that “when trying to maximize hypertrophy, one should employ a ROM that emphasizes training at long muscle lengths, while also employing a repetition tempo of between 2 and 8 seconds.”

The long muscle length recommendation, however, seems to be much more nuanced than presented. Regardless, the paper sparked a lot of conversation—and in many ways, underplayed the importance of exercise technique. Or at least, it admitted the direct evidence for many technique-based recommendations was lacking.

Do cheaters prosper? A closer look at the new study

As a follow-up, a new study titled “Do Cheaters Prosper?” set out to answer that question directly. Conducted by researchers at CUNY Lehman College with contributions from well-known fitness educator Jeff Nippard, this is one of the most direct investigations we’ve seen on this topic.

Here’s how they did it:

  • Participants: 30 untrained men and women

  • Design: Each person trained both arms, but in two different ways

    • One arm: strict, controlled form

    • Other arm: used external momentum (aka cheat reps)

  • Exercises: Bicep curls and tricep pushdowns

  • Training duration: Twice a week for 8 weeks

  • Sets/reps: 4 sets of 8–12 reps per arm, going to momentary failure

  • Measurement: Muscle thickness via ultrasound at 55% and 65% of upper arm length

What did they find?

Both arms experienced muscle growth—no surprise there. But here’s the key finding:

There was no significant difference in muscle growth between the cheat reps and strict reps.

That’s right—using momentum didn’t help, but it didn’t hurt either.

Participants saw moderate hypertrophy, with changes in muscle thickness ranging between 5.6% and 14.7%.

Interestingly, total training volume (the amount of weight lifted over the 8 weeks) was significantly higher in the cheat rep condition. Some participants lifted nearly double the volume with the cheat arm.

And yet… muscle growth remained the same. Why?

The likely explanation is that the added momentum shifted some of the effort away from the target muscles (biceps and triceps) and onto supporting muscles like the shoulders, back, and legs. So, even though the load increased, the stimulus to the target muscle likely stayed about the same.

So should you use cheat reps?

Cheat reps aren’t necessarily bad. In fact, this study shows they can be used without compromising muscle growth—at least in beginners performing isolation exercises.

But that doesn’t mean cheat reps are superior, or that strict form is irrelevant. Strict form is still your safest bet, especially over longer periods or when performing complex, multi-joint movements.

The study did report some minor complaints (like elevated heart rate during cheat reps), but no serious injuries. Still, the authors cautioned that momentum-based lifting could increase joint and tendon stress over time if form breaks down.

Also, keep in mind:
This study looked at beginners doing single-joint exercises. We still don’t know how cheat reps affect advanced lifters or compound lifts like deadlifts or rows.

Reframing the discussion: is this eccentric overload?

Let’s think critically about why both training arms saw growth.

It’s likely that the cheat reps created what’s known as eccentric overload. Using momentum during the concentric phase (lifting the weight) allows for heavier loads to be lifted overall. But the key detail is this: the cheat rep group still controlled the eccentric (lowering) phase for ~2 seconds.

In this light, the study could be reframed as comparing traditional isotonic training to eccentric overload training—which would explain the similar results.

The takeaway?

Cheat reps work… if you control the negative.

Final thoughts: cheat reps as training tools

It’s worth noting that the cheat group likely spent less time at long muscle lengths. That’s an important insight because it challenges the prevailing belief that long muscle lengths are the most critical factor in hypertrophy.

So here’s the big picture:

✅ Cheat reps, used carefully, aren’t muscle killers
✅ You can use them to push past failure or add training variety
✅ But they shouldn’t replace strict form as your default

Think of cheat reps like hot sauce:
Great for a little extra kick, but not something to pour over every workout.

Train with purpose. Know why you’re doing what you’re doing. That’s how real progress happens. Learn about which tempo wins for muscle growth here.

📚 Reference:

Oikawa SY, Miller G, Janas G, Nippard J, Jenkins ND, Tinsley GM, Schoenfeld BJ. (2024). “Do Cheaters Prosper? A Within-Subject Investigation into the Effects of Cheat Repetitions on Muscle Hypertrophy and Strength.”
Read the full study on ResearchGate

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