The Truth About the Hypertrophy Rep Range

If you’ve ever looked up training information related to muscle growth, you’ve likely encountered the idea that the 8-12 reps repetition range is ideal for hypertrophy. 

But is this concept really the golden rule for muscle building, or is the truth far more nuanced? 

Let’s break it down.

The Hypertrophy Rep Range: A Brief Introduction

 For years, conventional wisdom has promoted the following training guidelines:

• Low Repetitions (1 - 5 reps): Best for building maximal strength with heavy loads.
• Moderate Repetitions (8 - 12 reps): Traditionally viewed as the optimal range for muscle hypertrophy.
• High Repetitions (12+ reps): Generally used for muscular endurance and lighter load work.

This framework stems from the SAID (Specific Adaptation to Imposed Demands) principle, which tells us that the body adapts specifically to the nature of the training stress placed upon it. In theory, lifting heavy builds strength, while moderate reps maximise the balance of load and volume for muscle growth.

But how well does the evidence support these ideas?

Mechanical Tension: The Real Driver of Hypertrophy

The most important factor for muscle growth is mechanical tension - the force experienced by muscle fibres during resistance training (Schoenfeld et al., 2017).

Training volume (sets x reps x load) matters, but its role is to accumulate enough mechanical tension over time. In other words, rep range itself isn’t the critical factor - what matters is that each set generates enough tension and is taken close to failure.

For example, a meta-analysis by Schoenfeld et al. (2017) found that when total volume is equated, muscle growth is similar across a wide range of reps, from low to high. The key factor? Effort. Sets taken close to failure stimulate hypertrophy, regardless of whether you're lifting heavy for low reps or lighter for high reps.

A 2016 study by Morton et al. reinforced this, showing that both high-load, low-rep and low-load, high-rep training led to significant hypertrophy - as long as effort was high.

Why is the 8-12 Rep Range Popular?

Even though research confirms hypertrophy isn’t locked into one rep range, the moderate range remains popular for practical reasons:

• Balanced Intensity and Volume: Allows for high mechanical tension without excessive joint stress.
• Ease of Monitoring Effort: Using tools like Reps in Reserve (RIR) or Rate of Perceived Exertion (RPE) is more straightforward in this rep range. Trying to gauge effort on a set of 30 reps can be much more challenging.
• Progressive Overload: It’s typically easier to make incremental load increases in the 8-12 rep range, ensuring steady progression over time.

So, Is There a “Magic” Rep Range for Hypertrophy?

The answer is: Not exactly.

The so called hypertrophy range isn’t a mystical zone where gains happen only within strict numerical boundaries. Instead, it represents a practical compromise between intensity and volume that enables most people to effectively accumulate work while minimising the risk of injury. It’s a guideline - a starting point that works well for many - rather than a rigid rule.

If your goal is muscle growth, consider these evidence-based strategies:

• Focus on Volume: Aim to progressively increase the total work done over time.
• Train Close to Failure (1-2 RIR): Mechanical tension is key, regardless of rep range.

• Mix It Up: Incorporate a variety of rep ranges to optimise muscle hypertrophy while reducing joint stress and minimising injury risk. 

Conclusion

While the 8-12 rep range has long been the go to for hypertrophy, muscle growth is about mechanical tension, progressive overload, and volume - not arbitrary rep numbers.

That said, 8-12 remains a useful range because it maximises load and volume without excessive fatigue.

But for long term muscle growth, varying rep ranges based on recovery, exercise selection, and individual response is key.

References:

• Schoenfeld (2010). The mechanisms of muscle hypertrophy and their application to resistance training. Journal of Strength and Conditioning Research.
• Schoenfeld et al. (2017). Effects of different volume-equated resistance training loading strategies on muscular adaptations in trained men. Journal of Strength and Conditioning Research.
• Morton et al. (2016). Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men. Journal of Applied Physiology.