Are you grinding out every last rep on your single-set finishers, thinking it's the only way to grow? Or maybe you're short on time and wondering if one all-out set is enough to make progress. It's a classic debate in the gym: is training to absolute muscular failure the secret sauce, or can you get the same results by leaving a couple of reps in the tank?
A new study published in Medicine and Science in Sports and Exercise tackles this exact question, specifically in the context of time-efficient, single-set training for people who already lift. Let's break down what the researchers found and what it means for your workouts.
(Note: This analysis is based on the study's abstract, as the full text is not yet publicly available.)
The Research: Failure vs. Reps-in-Reserve Head-to-Head
The goal of this study was simple: compare the effects of a single set taken to failure versus a single set with a submaximal effort.
Researchers took 42 young, resistance-trained men and women and split them into two groups for an 8-week program. Both groups trained twice a week, performing a single set of nine exercises that covered all the major muscle groups.
Here was the key difference:
- The FAIL Group: This group performed every single set with maximal effort, pushing to the point of muscular failure where they couldn't complete another rep with good form.
- The 2-RIR Group: This group performed the exact same exercises but stopped each set with two repetitions-in-reserve (2-RIR). Essentially, they finished knowing they could have done two more reps if they had to.
Before and after the eight weeks, the scientists measured changes in muscle thickness (biceps, triceps, and quads), strength, power (using a countermovement jump), and local muscular endurance.
The Results: What Actually Happened?
After eight weeks of consistent training, both groups made solid progress. This is the first big takeaway: single-set routines can be a very effective and time-efficient strategy, even for people who are already trained and may be used to higher-volume programs.
But what about the differences between the groups?
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Muscle Growth (Hypertrophy): The results here tended to favor the FAIL group. While both groups grew, the lifters who went to failure saw slightly better gains in muscle thickness. The researchers were quick to point out, however, that the absolute differences between the groups were "generally modest."
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Power: For changes in countermovement jump height, the results also favored the FAIL group. However, the abstract notes there was "no clear statistical support" for this finding, meaning the advantage wasn't strong enough to be conclusive.
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Strength & Endurance: This is where things get interesting. For increases in both maximal strength and local muscular endurance, there were no significant differences between the groups. Both the FAIL and 2-RIR lifters got similarly stronger and improved their endurance at the same rate.
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Bonus Finding - RIR Accuracy: The study also found that participants got better at estimating their RIR over the eight weeks, especially on the bench press compared to the squat. This confirms what many coaches already know: judging RIR is a skill that improves with practice.
Key Takeaways for Your Training
This study provides some clear, practical guidance for structuring your workouts, especially when you're pressed for time.
1. Single-Set Training is a Viable Tool
Don't let anyone tell you that you need to do 3-4 sets of every exercise to make gains. This study adds to a growing body of evidence showing that one hard, focused set can be a powerful stimulus for adaptation, even in trained individuals.
2. For Strength, Failure is Not Mandatory
If your primary goal is getting stronger, you can feel confident ending your single sets with a couple of reps left in the tank. You'll get the same strength benefits as going to failure, but likely with less systemic fatigue, which can improve your recovery for subsequent workouts.
3. For Hypertrophy, Failure Might Give You a Small Edge
If building muscle is your number one priority, pushing that single set all the way to failure may provide a slight, but not massive, advantage. The key word here is modest. You have to ask yourself if the extra fatigue and recovery demands are worth that small potential boost in growth. For some, the answer is yes. For others, the consistent, less-draining approach of RIR training is a smarter long-term play.
The Bottom Line
The choice to train to failure in a single-set routine isn't a simple yes or no—it's a strategic decision based on your goals.
- If you're focused on strength or general fitness, stopping 2 reps shy of failure is just as effective and likely more sustainable.
- If you're chasing every last bit of muscle growth, taking that one set to failure could give you a minor edge.
Ultimately, this research empowers you with options. It confirms that a single, high-effort set is a potent training tool, and how you define that "high effort" can be tailored to what you want to achieve.
Reference
Hermann T, Mohan AE, Enes A, et al. Without Fail: Muscular Adaptations in Single-Set Resistance Training Performed to Failure or with Repetitions-in-Reserve. Med Sci Sports Exerc. 2025. https://pubmed.ncbi.nlm.nih.gov/40249908/