What if the secret to building muscle and strength wasn’t grinding to failure on every set, but instead knowing when to stop? The recent study by Martikainen and colleagues (2025) challenges one of the most entrenched beliefs in resistance training—that failure is king—by exploring how varying proximity-to-failure impacts muscular adaptations and the accuracy of repetitions-in-reserve (RIR) estimation. Their findings suggest that mixing effort levels across sessions may be just as effective as always pushing to the brink, with added benefits in skill development and localized hypertrophy. But this raises deeper questions: Are we overvaluing the “no pain, no gain” mentality at the expense of smarter, more sustainable training? Could teaching athletes to better gauge effort be just as important as prescribing sets and reps? And how might these insights reshape the way coaches design programs for long-term progress?

Martikainen, O., Niiranen, H., Rytkönen, T., Schoenfeld, B. J., Ahtiainen, J. P., & Hulmi, J. J. (2025). Influence of varying proximity-to-failure on muscular adaptations and repetitions-in-reserve estimation accuracy in resistance-trained individuals. Journal of Science in Sport and Exercise.

Introduction

The introduction establishes the context by highlighting the ongoing debate in resistance training research regarding the optimal proximity to muscular failure. While training close to failure has traditionally been considered necessary to maximize hypertrophy and strength gains, more recent evidence suggests that leaving repetitions in reserve (RIR) can still produce meaningful adaptations. The authors note that most prior studies have compared fixed distances from failure (e.g., always training at RIR1 or RIR3), but little is known about the effects of varying proximity to failure across a training program. This gap is important because athletes and coaches often adjust effort levels week to week, either intentionally for periodization or unintentionally due to fatigue and recovery demands.

This study emphasizes the practical challenge of accurately estimating RIR. Since RIR is a subjective measure, its reliability depends on the lifter’s ability to judge how many repetitions they can perform before reaching failure. Inaccurate estimation could undermine training prescriptions, making it essential to understand whether repeated exposure to different proximities to failure improves estimation accuracy.

Finally, the authors frame their study as addressing two key questions:

• Does varying proximity to failure across a training cycle lead to different muscular adaptations compared to consistently training very close to failure?
• Does exposure to different RIR targets enhance the accuracy of lifters’ ability to estimate repetitions in reserve?

By situating these questions within both theoretical debates and practical coaching concerns, the introduction sets up the rationale for the experimental design. The authors argue that resolving these issues could refine resistance training guidelines, balancing effectiveness with sustainability and athlete autonomy.

Theoretical Considerations

The theoretical foundation of Martikainen et al. (2025) rests on several interconnected concepts in resistance training science.

Proximity to Failure and Muscular Adaptation

• Traditional view: Training to muscular failure (the point where no further repetitions can be completed with proper form) has long been considered essential for maximizing hypertrophy and strength.
• Emerging evidence: Research indicates that adaptations can occur even when sets are terminated before failure, …