Training to Failure vs Sub-Maximal Training: What Research Says About Muscle Growth
Key insights: 60-second read
- Training to failure is not clearly required for muscle growth - in this 2019 study, sub-maximal training produced greater increases in several measures of muscle size when training volume was similar.
- The study compared two training approaches over 10 weeks - one used repetition-max loads that reached failure on the final set of each exercise, while the other used planned sub-maximal loads.
- Fatigue and recovery may help explain the difference - training to failure can prolong recovery, which may matter when hard training is performed repeatedly.
- The wider evidence is more nuanced - later reviews have not found a clear hypertrophy advantage for momentary muscular failure over non-failure training.
For decades, training to failure - pushing a muscle until you cannot complete another repetition with good technique - has been a popular strategy for building muscle. But does taking every set to failure actually produce more muscle growth?
A 2019 study published in Sports compared training to failure with a planned sub-maximal approach in well-trained men. Interestingly, the sub-maximal group showed greater increases in several measures of muscle size over 10 weeks.
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Does Training to Failure Build More Muscle?
The theory behind training to failure is straightforward: as a set becomes harder, more motor units are recruited to keep producing force. Taking a set to the point where another repetition cannot be completed therefore seems like it should provide the strongest possible stimulus for growth.
There is a problem, though. The strongest possible stimulus is not necessarily the best overall training strategy if it also creates substantially more fatigue.
Training to failure can increase acute fatigue and prolong recovery. It may also make it harder to maintain performance and technique as a session progresses. These effects do not mean failure training is inherently unsafe or ineffective, but they are important when deciding how often to use it.
What Did the Study Actually Test?
The researchers studied 15 well-trained men who completed resistance training three times per week for 10 weeks. The participants had an average of almost eight years of consistent resistance-training experience.
Key study design features
- Participants: 15 well-trained males, aged approximately 23-31 years, who completed the intervention.
- Training: 3 resistance-training sessions per week for 10 weeks, using a block-periodised program.
- Training approach: One group used repetition-maximum loading, with the final set of each exercise taken to momentary muscular failure. The other used planned relative intensities and did not train to failure.
- Training volume: The groups followed matched set-and-repetition prescriptions, and estimated volume load did not differ significantly between groups.
- Muscle measurements: Muscle thickness and anatomical cross-sectional area were assessed using ultrasound, while muscle fibre size was assessed using biopsies of the vastus lateralis.
- Other training: Both groups also completed the same sprint training twice per week.
Importantly, this was not simply a comparison of "hard training" versus "easy training". Both groups trained seriously. The main difference was how the training load was prescribed and how often the sets were taken to failure.
What Did the Study Find?
The sub-maximal group showed greater increases in several measures of muscle growth. Type I and type II muscle fibre cross-sectional area, anatomical cross-sectional area and muscle thickness all increased significantly in the relative-intensity group, while the repetition-maximum group showed a significant increase in muscle thickness.
Between-group effect sizes also favoured the relative-intensity approach for several measures of fibre size and whole-muscle size.
So, within this particular study, training to failure did not produce greater muscle growth despite similar estimated training volume.
And this is where the wider evidence becomes important. Later systematic reviews have generally found no clear evidence that momentary muscular failure is superior to non-failure training for hypertrophy. In other words, the 2019 study is an interesting piece of evidence, rather than proof that stopping short of failure will always produce more muscle. A 2022 systematic review and meta-analysis, for example, found no evidence that momentary failure was superior to non-failure training for muscle hypertrophy.
Why Might Stopping Short of Failure Help?
From a physiotherapy perspective, this is where the study becomes particularly interesting. Building muscle is not just about what happens during a workout. It is also about how well you recover and how consistently you can train afterwards.
The authors suggested that better fatigue management may have contributed to the greater adaptations seen in the relative-intensity group. This is consistent with other research showing that resistance training to failure can delay recovery of neuromuscular performance by around 24-48 hours compared with non-failure protocols in trained men performing squats and bench press.
Recovery depends on the exercise, training volume, load, training status and the individual. And, it does highlight an important principle: the best training stimulus is not necessarily the one that creates the most fatigue.
In my clinical experience, this distinction matters. I often see people who are very motivated to train hard, but who judge the quality of a session by how exhausted they feel afterwards. Fatigue can be part of productive training, but it is not the same thing as adaptation. If excessive fatigue reduces the quality or consistency of your subsequent sessions, it may work against your longer-term goals.
What Are the Limitations of This Research?
These results are interesting, but they need to be kept in context.
- Small sample: Only 15 participants completed the study, so larger studies are needed to confirm the findings.
- Limited population: The participants were well-trained young men. We cannot assume the same results will apply to women, older adults, beginners or people with different training backgrounds.
- Specific training program: The study used a structured block-periodised program with relatively high training intensities. The findings may not translate directly to every style of hypertrophy training, particularly higher-repetition bodybuilding programs.
- Multiple factors changed together: The groups differed in their load prescription and failure strategy, so the study cannot tell us that fatigue alone caused the difference in muscle growth.
- Short duration: Ten weeks is enough to detect meaningful changes, but it does not tell us what would happen over many months or years.
How Close to Failure Should You Train?
For most people, the practical message is not "never train to failure". It's that you probably don't need to take every set to absolute failure to stimulate muscle growth.
- Leave some repetitions in reserve: Challenging sets that finish before true failure can still provide a strong stimulus for muscle growth.
- Use failure strategically: Training to failure can be useful on selected exercises or sets, rather than being treated as a requirement for every set.
- Prioritise recovery: If frequent training leaves you carrying substantial fatigue from one session into the next, reducing how often you train to failure may be worth considering.
- Protect technique: If fatigue causes your technique to deteriorate, stopping the set earlier may be a sensible way to maintain exercise quality.
- Look at the whole program: Training volume, load, exercise selection, nutrition, sleep and recovery all contribute to your ability to build muscle. Failure is only one variable.
The exact number of repetitions you should leave in reserve will depend on the exercise, load, training goal and individual. The research does not support one universal "magic" number for everyone.
Conclusion: Is Training to Failure Necessary for Muscle Growth?
The 2019 study provides an interesting challenge to the idea that more fatigue automatically means more muscle growth. In this group of well-trained men, planned sub-maximal training produced greater increases in several measures of muscle size despite similar estimated training volume.
More broadly, the research does not show that training to failure is either essential or useless. It can build muscle, but current evidence suggests you do not need to reach momentary failure on every set to achieve hypertrophy. Managing fatigue so that you can train consistently, recover well and maintain good-quality work may be just as important.
This research has certainly given me pause for thought in my own training - hopefully, it provides a useful perspective for you, too.
Do you incorporate training to failure in your routine? How has it affected your recovery and progress? Share your experiences in the comments below!
Frequently Asked Questions
Do I need to train to failure to build muscle?
No. Training to failure can stimulate muscle growth, but current evidence does not show that momentary muscular failure is necessary for hypertrophy. This 2019 study actually found greater increases in several measures of muscle size with planned sub-maximal training.
Is training to failure better for muscle growth?
Not consistently. The 2019 study found greater hypertrophy-related changes in the sub-maximal group, while later systematic reviews have generally found no clear advantage for momentary muscular failure over non-failure training.
How many reps should I leave in the tank?
There is no single number that is right for everyone. A challenging set performed short of failure can still be effective, and the appropriate amount of repetitions in reserve depends on the exercise, load, training goal and individual. The important thing is that the set is sufficiently challenging while allowing you to maintain good technique and recover for future training.
Can beginners use this approach?
Yes, although this particular study involved well-trained men, not beginners. Beginners can build muscle without taking every set to failure, and learning good technique while managing fatigue is a sensible foundation for progressive resistance training.
Does training to failure slow recovery?
It can. Research comparing failure and non-failure resistance training has found slower recovery of neuromuscular performance after failure protocols, with differences lasting around 24-48 hours in some trained men. The exact recovery cost varies with the exercise, training volume, load and individual.
One key insight
Training to failure can build muscle, but you do not need to reach failure on every set. The 2019 study found greater muscle-size adaptations with planned sub-maximal training, while later reviews suggest that momentary failure is not clearly superior for hypertrophy.
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