10 Reps vs. 20 Reps: Does Rep Range Actually Matter for Building Muscle?

Walk into any gym and you'll hear strong opinions about rep ranges. Some swear by heavy sets of 5 for strength. Others insist that 10-12 reps is the hypertrophy sweet spot. A few argue for high reps of 20 or more for conditioning and endurance.

So what does the research actually say? The answer might liberate you from worrying about finding the "perfect" number.

What the Study Found

A recent study put the rep range debate to the test00185-9/abstract), splitting participants into three groups: one trained with a 10-repetition maximum (heavier weight), another with a 20-repetition maximum (lighter weight), and a control group that didn't train. Both training groups performed two lower-body workouts per week for six weeks, completing each set to concentric failure.

Muscle thickness increased significantly in both training groups, with no meaningful difference between those performing 10 and 20 repetitions.

Strength improved across all exercises in both training groups. Whether participants used heavier weights for fewer reps or moderate weights for more reps, the outcomes were essentially the same.

The Common Factor: Training to Failure

The key detail in this study is that both groups trained to failure. They didn't stop when they hit a target number; they continued until they couldn't complete another rep with good form.

This appears to be the critical variable. When intensity is equalized by pushing to failure, the specific rep range matters less. Your muscles don't count reps. They respond to mechanical tension, metabolic stress, and muscle damage, all of which can be achieved across different rep ranges when effort is maximal.

Why Both Approaches Work

Lower reps, heavier weight:

• Higher mechanical tension per rep
• Greater neural adaptations
• Less time under tension per set
• Lower metabolic fatigue per set

Higher reps, lighter weight:

• Greater metabolic stress
• More time under tension
• Potentially safer for those learning movements
• Can be less intimidating psychologically

Both stimuli trigger the muscle protein synthesis that leads to growth. The pathways may differ slightly, but the end result is similar when effort is matched.

Practical Applications for Training

This research has several practical implications:

Stop obsessing over specific numbers. Whether you're doing 8 reps or 15 reps, if you're pushing close to failure with good form, you're stimulating growth.

Match rep range to your goals. While both work for muscle building, there are reasons to choose one over another:

• Training for maximum strength favors lower reps with heavier loads
• Training with injury limitations may favor higher reps with lighter loads
• Training for muscular endurance specifically benefits from higher rep work

Consider psychological factors. Some people feel more confident pushing hard with lighter weights. Others find they can only give true effort when the weight feels heavy. Choose what allows you to push hardest.

Use both approaches. There's no rule requiring you to pick one rep range forever. Periodizing between heavier and lighter training phases exposes your muscles to different stimuli.

The Importance of Good Form

Both groups in the study completed reps with proper form. This is crucial. Training to failure with poor form doesn't produce the same results and dramatically increases injury risk.

As you fatigue, form naturally degrades. The skill is pushing hard enough to stimulate growth while stopping before technique breaks down completely. This takes practice and self-awareness.

For compound movements like squats and deadlifts, leaving 1-2 reps in the tank is often prudent. For isolation movements with lower injury risk, pushing to true failure is more feasible.

Full Range of Motion Still Matters

Whatever rep range you choose, full range of motion remains important. The study participants performed exercises through complete movement patterns. This ensures the muscle is working through its full capacity and receiving adequate stretch.

Cutting range of motion short to hit a target rep number defeats the purpose. Better to do fewer reps through full range than more reps with partial movement.

Progressive Overload Matters More

While rep ranges get a lot of attention, progressive overload is more important for long-term results. You need to challenge your muscles increasingly over time.

This can happen through:

• Adding weight to the bar
• Adding reps at the same weight
• Adding sets
• Improving form and range of motion
• Reducing rest periods

If you're doing the same weight for the same reps month after month, you're not progressing. The rep range you choose matters less than whether you're consistently challenging yourself more.

The Bottom Line

The research is clear: when training to failure, 10 reps and 20 reps produce similar muscle growth and strength gains. Your muscles don't care about the number on your program; they respond to the effort you put in.

Stop searching for the magic rep range. Instead, focus on:

1. Training close to failure (1-3 reps in reserve, or to actual failure on safer movements)
2. Using full range of motion
3. Maintaining good form
4. Progressively overloading over time
5. Being consistent

Whether you prefer heavier weights for fewer reps or lighter weights for more reps, you can build muscle and strength with either approach. Choose what you enjoy, what feels safe for your body, and what you'll actually do consistently.

Use the AFT Calculator to track how your training translates to performance on specific events, and remember that showing up and working hard matters more than finding the theoretically perfect rep scheme.