Training to Failure: What Science Says About Proximity to Failure

One of the most debated topics in resistance training is how close you need to push to failure to maximize muscle growth and strength. For years, bodybuilders have insisted that training to failure is essential, while some strength coaches argue it's unnecessary and increases injury risk.

A groundbreaking 2024 meta-analysis from Florida Atlantic University finally provides some clarity.

What Does "Proximity to Failure" Mean?

Before diving into the research, let's clarify the terminology. Repetitions in reserve (RIR) is a way to measure how close you are to failure:

• 0 RIR = Training to failure (you couldn't do another rep)
• 2 RIR = You could have done 2 more reps
• 5 RIR = You could have done 5 more reps

The question scientists wanted to answer: how does the distance from failure affect your gains?

The Research: 55 Studies Analyzed

Researchers analyzed data from 55 studies examining how different levels of proximity to failure affected both strength and hypertrophy outcomes [1]. They looked at the relationship between RIR and muscular adaptations in trained individuals.

Key Finding #1: Failure Matters for Hypertrophy

The data showed a clear pattern: muscle growth benefits from training closer to failure.

"The closer you are to failure when you stop your sets, the more muscle growth you tend to see." — Robinson et al., 2024

This makes sense from a physiological standpoint. Training closer to failure creates greater metabolic stress and motor unit recruitment, both key drivers of muscle hypertrophy.

Key Finding #2: Failure Doesn't Matter for Strength

Here's where it gets interesting: strength gains showed no significant difference whether you trained to failure or stopped well short of it.

Whether you stop 5 reps short of failure or grind to the absolute last rep, your strength improvements appear to be similar. This is a game-changer for those who want to maximize strength without the added fatigue and recovery cost of training to failure.

Practical Applications

Based on this research, here's how to apply these findings:

For Muscle Growth (Hypertrophy)

• Train within 0-3 RIR for optimal muscle growth
• You don't need to hit true failure every set, but get close
• This provides the best balance of growth stimulus while managing fatigue

For Strength

• Stop 3-5 reps short of failure
• Heavier loads with less proximity to failure work just as well
• This approach minimizes systemic fatigue and allows for more frequent training

The Nuance: Failure Isn't Required, But It Helps

The 2025 study "Without Fail" published in Medicine & Science in Sports & Exercise found that both training to failure AND training with 2 RIR produced "appreciable gains" in most outcomes [2]. The differences between conditions were "modest" — meaning both approaches work.

However, the relationship between proximity to failure and hypertrophy remains consistent: closer to failure = slightly better muscle growth.

Why Might Failure Help Hypertrophy?

• Greater motor unit recruitment — More muscle fibers are activated
• Increased metabolic stress — The "pump" creates a hypertrophic environment
• Mechanical tension — More time under tension near failure
• Perceptual accuracy — Training closer to failure improves your ability to gauge effort

The Bottom Line

You don't need to train to failure to build muscle or get stronger. However:

• For hypertrophy: Training within 0-3 RIR appears optimal
• For strength: 3-5 RIR with heavier loads works just as well as failure training
• The middle ground: Most trainees will do well with 1-3 RIR — close enough for growth, not so close that you're destroying recovery

What This Means for Your Training

If you've been grinding every set to failure and feeling burnt out, here's permission to relax a bit. You can leave 1-2 reps in the tank and still make excellent progress — especially for strength.

For muscle growth, don't be afraid to push close to failure. The research suggests it's worthwhile. Just don't mistake "push hard" for "destroy yourself" — the difference in gains doesn't justify the extra recovery time.

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References

[1] Robinson ZP, Pelland JC, Refalo MC, Jukic I, Steele J, Zourdos MC. "Exploring the Dose-Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions." Sports Medicine. 2024.

[2] "Without Fail: Muscular Adaptations in Single-Set Resistance Training Performed to Failure or with Repetitions-in-Reserve." Medicine & Science in Sports & Exercise. September 2025.