Why Bodybuilders Use Higher Reps (It Has Nothing to Do With Muscle Growth)

Your muscles don't care about rep ranges. That's the short version, and the research backs it up clearly.

A meta-analysis of 21 studies found that muscle growth was virtually identical between low-load and high-load training, and a separate network meta-analysis of 28 studies with 747 adults confirmed the same thing: as long as you're training close to failure, the rep range you use doesn't change how much muscle you build. Six reps or fifteen reps, the hypertrophy signal is the same.

So the rep range is just a vehicle. What drives growth is proximity to failure, not the load you pick to get there.

That means the reason to use higher reps isn't about building more muscle. It's about something else entirely, and that something else is the reason experienced lifters are still training hard at fifty while others have already collected their second or third overuse injury.

To understand why, you need to understand a mismatch that happens inside your body every time you start training hard.

When you begin a strength training program, your muscles respond quickly. They get stronger within a matter of weeks because of something called neural adaptation, which is your nervous system getting better at recruiting the muscle fibers you already have. Structural muscle growth starts layering on top of that over the following months. The point is that muscle tissue is highly responsive and changes fast.

Your tendons don't work that way.

Tendons are made primarily of collagen, and collagen remodeling is slow. In one study tracking both muscle strength and tendon stiffness over a training period, muscle strength gains appeared within two months, but tendon stiffness didn't change significantly until after that two month mark, and even then the adaptation lagged behind the muscle considerably.

So you have a situation where your muscles are getting significantly stronger and producing significantly more force, but the connective tissue attaching those muscles to your bones is still operating at its old capacity.

Think of it like upgrading the engine in a car without upgrading the brakes. The car can go faster. It just can't stop as reliably.

That force mismatch is where something called tendinopathy comes from, which is the medical term for overuse damage to tendons, the kind that shows up as patellar tendon pain, Achilles problems, shoulder impingement, elbow issues. Research on young athletes found that rapid muscle strength gains without corresponding tendon stiffness increases directly elevate the strain placed on tendons during training, and that elevated strain is what tips tissue from adaptation into breakdown.

This isn't a rare edge case. It's a predictable consequence of asking a tissue that adapts slowly to keep up with a tissue that adapts quickly.

Now here's where the rep range conversation actually becomes relevant.

Heavier loads mean higher absolute force on tendons per rep. When you train in the one to five rep range or even the six to eight range consistently across all your exercises, you're applying high mechanical stress to connective tissue repeatedly, and you're doing it before your tendons have built the capacity to absorb that stress without accumulating damage.

Moderate and higher rep ranges with lighter loads reduce the peak force on tendons per rep, even when the total training volume and the proximity to failure are kept the same. You're still generating a strong enough signal to drive muscle growth, but you're distributing the mechanical demand differently.

The injury data makes this visible in a way that's hard to argue with.

Bodybuilders, who have trained with moderate loads and higher rep ranges for decades as a matter of culture, have an injury rate of somewhere between 0.24 and 1.0 per 1,000 training hours. Powerlifters, who train specifically in low rep ranges with maximal and near-maximal loads, come in between 1.0 and 4.4 per 1,000 hours. Strongman athletes, who combine maximal loads with high fatigue and awkward positions, sit between 4.5 and 6.1.

That's roughly a four-to-one gap between bodybuilders and powerlifters, and the bodybuilding community arrived at this outcome empirically, without knowing the tendon adaptation research, just by observing over decades what kept people training and what got them hurt.

The practical structure this leads to is a stratification by exercise type rather than a single rep range for everything.

For compound movements where you're moving the most total load and the tendons are under significant stress, something in the six to ten rep range balances stimulus with connective tissue demand reasonably well. For accessory work where you're targeting specific muscles with less total system stress, ten to fifteen reps gives you plenty of hypertrophy signal with less joint loading. For anything that creates direct stress on a vulnerable joint, a shoulder lateral raise, a tricep extension, anything with a long moment arm at a compromised angle, pushing into the fifteen to twenty-five rep range keeps the load low enough that you're asking your tendons for a lot less per rep.

Across all of those ranges, you still push close to failure. That part doesn't change. The proximity to failure is what drives the adaptation. The rep range is just managing what happens to your connective tissue in the process.

The framing most people use when they think about rep ranges is: what will make my muscles grow the most? And that's a question with a straightforward answer. Almost any rep range works if you train hard enough.

The better question is: what rep range lets me keep training hard a year from now, five years from now, twenty years from now? Because the limiting factor on long-term muscle growth isn't the rep range you chose. It's whether you can stay in the gym consistently enough for the adaptations to compound.

Tendons don't stop you when they're adapting. They stop you when you've outpaced them for long enough that the damage accumulates into something that forces rest. By the time you feel it, the mismatch has already been building for weeks.

The lifters who understood this earliest didn't think of higher reps as a concession. They thought of it as the strategy that lets you keep applying the stimulus that matters without burning down the connective tissue that makes the whole system work.

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References

1. Schoenfeld BJ, Grgic J, Ogborn D, Krieger JW. Strength and hypertrophy adaptations between low- vs. high-load resistance training: a systematic review and meta-analysis. Journal of Strength and Conditioning Research. 2017;3112:3508-3523. Finding: From 21 studies, muscle hypertrophy was similar between low-load and high-load conditions. Source
2. Lopez P, Radaelli R, Taaffe DR, et al. Resistance training load effects on muscle hypertrophy and strength gain: systematic review and network meta-analysis. Medicine and Science in Sports and Exercise. 2021;536:1206-1216. Finding: No differences in muscle hypertrophy between low, moderate, and high loads when training to volitional failure 28 studies, 747 adults. Source
3. Kubo K, Ikebukuro T, Yata H, et al. Time course of changes in muscle and tendon properties during strength training and detraining. Journal of Strength and Conditioning Research. 2010;242:322-331. Finding: Muscle strength gains appeared within 2 months, but tendon stiffness did not change significantly until 2+ months. Source
4. Mersmann F, Bohm S, Arampatzis A. Imbalances in the development of muscle and tendon as risk factor for tendinopathies in youth athletes. Frontiers in Physiology. 2017;8:987. Finding: Rapid muscle strength gains without corresponding tendon stiffness increases create elevated tendon strain and tendinopathy risk. Source
5. Keogh JWL, Winwood PW. The epidemiology of injuries across the weight-training sports. Sports Medicine. 2017;473:479-501. Finding: Bodybuilding injury rate 0.24-1.0 per 1000 hours. Powerlifting 1.0-4.4 per 1000 hours. Strongman 4.5-6.1 per 1000 hours. Source

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