Resistance training is the primary form of exercise to promote muscular strength and hypertrophy. One of the main methods to increase the hypertrophic potential of resistance training is to manipulate various training variables. These include adapting training volume to match the recovery ability of an athlete, and tailor set- and repetition schemes to suit individual training goals.
Another of the main modifiable variables with the potential to enhance the training response is training to failure.
A US Army physician introduced the concept of training to failure to enhance the potential of muscle growth in the 1940s. Since then, it has been a staple training principle of bodybuilders and strength athletes. While the other main training principles mentioned have been extensively researched in recent years, training to failure has been the center of far less scientific attention.
The standard medical reference work Current Medical Diagnosis and Treatment concludes that training to failure is a requirement to maximize muscular hypertrophy.
Contrary to this statement, a recent meta-analysis concludes that non-failure training likely produces similar results in the form of muscle growth as training to failure, provided the total training volume is equal.
Training to Failure Defined
The most common form of muscular failure, defined as the inability to complete a repetition in a full range of motion at a specific overload without the assistance of a training partner or compromising a prescribed form.
Eccentric failure is the inability to prevent the eccentric contraction of a repetition from occurring at a shorter duration than prescribed.
Isometric failure is the inability to prevent an eccentric contraction from occurring, despite the attempt to maintain the current position.
Absolute failure can be described as the inability to perform another repetition even with assistance or through cheating methods.
Concentric failure has been the focus of the majority of the research on the topic in regards to muscular strength, hypertrophy, and recovery.
Proposed Mechanisms of the Purported Benefits of Training to Tailure
Motor Unit Recruitment
Full motor recruitment has long been considered essential for a muscle to grow bigger and stronger.3 A motor unit consists of a motor neuron and the muscle fibers that neuron innervates. The central nervous system activates these motor units as the muscular workload demands it, and they work in unison to coordinate muscle contractions.
To perform a heavy set to completion, a high level of force is required to move the weight. The central nervous system recruits all motor units from the start, leading to the activation of all muscle fibers.
When training with a low to moderate load, however, it takes longer to recruit the larger motor units. This is because there is no need for high levels of force to lift a lower load. As the low-load set continues, the central nervous system recruits more and larger motor units to maintain the force output and keep the weight moving.
When training to failure, cell swelling in the muscle occurs during metabolite accumulation.4 Some research indicate that this type of metabolite accumulation increases the release of anabolic hormones and has the potential to enhance muscle adaptations. Training to failure might therefore increase the anabolic stimulus of a set.
However, there is currently not enough evidence in support of this theory. It is unknown if this accumulation of metabolites following training to failure actually results in any meaningful increase in muscle protein synthesis. Until further research is available, this remains speculation.
Even if this theory turns out to be correct, there might very well exist a threshold where further accumulation of metabolites does not lead to any increased anabolic response. Thus, even non-failure training could be enough for this threshold to be reached.
The Effect of Training to Failure on Muscular Strength
The notion that training to muscular failure leads to greater gains in strength is an old and widespread one. Utilizing moderate to high loads is necessary to achieve substantial gains in strength, but not many studies have tried to determine if strength training to failure offers any significant benefit over non-failure training.
A 2016 meta-analysis assessed the results of available studies and showed that training to failure is not necessary for muscular strength.
5 In fact, the evidence indicated that non-failure training offers small but significant advantages over training to failure. It should, however, be noted that this difference, while significant, was so small that it might not be meaningful in practice.
Possibly, of greater concern and a reason to recommend against training to failure regularly would be the risks of injury and overtraining such a protocol might entail. Since both non-failure training and training to failure seem to elicit similar increases in strength, it might be prudent to limit the amount of maximum effort training to reduce these risks.
Experienced lifters might be expected to benefit more from training to failure than novice lifters, but the results from the 2016 meta-analysis do not indicate that this is the case.
It might seem logical that experienced lifters, being able to tolerate a higher training volume and intensity, might benefit from training to failure as an extra stimulus for strength gains. However, even experienced athletes showed slightly greater strength gains from non-failure training. It might be the case that trained subjects can push themselves further than untrained subjects within each repetition, leading to greater muscle activation within a set, eliminating the possible extra benefits of training to failure.
Over a longer period, it could be possible that training to failure might be a viable method to manipulate the training variables needed to progress enough so that even small differences can make a measurable difference.
In general, training to failure and not training to failure lead to comparable strength gains, although the increased risk of injury and overtraining may warrant a cautious approach to training to failure on a regular basis.
The Effect of Training to Failure on Muscular Hypertrophy
As with training for muscular strength, similar results by training to failure and not training to failure are likely. The results of a recent meta-analysis support this statement.6
Muscular hypertrophy seems to be similar following training to failure and following training where the sets are voluntarily terminated a couple of repetitions short of concentric failure. This seems to be the case at least when the training load is moderate to heavy and with an equated total training volume.
Training volume is one of the main drivers of muscular hypertrophy, behind only progressive overload training. If training to failure leads to an increase in training volume, it is likely that this will also serve as an incentive for greater muscle growth, as long as an athlete’s individual tolerance and opportunities permit proper recovery from such a training protocol.
If taking the majority of the sets of a training session to muscular failure leads to fatigue towards the end of the workout, however, this could mean a compromised ability to perform and thus a decrease of training volume. Under such circumstances, training to failure might lead to a less potent anabolic response to the training session, even if recovery ability is not an issue.
Training to Failure, Recovery and Overtraining
One of the potential drawbacks of training to failure is the build-up of fatigue. Not only can this lead to degradation of the training technique and increase the risk of injury, but going to failure on a regular basis can also be mentally challenging and have a negative effect on anabolic hormones. Training to failure too often for the recovery system to keep up can increase the risk of overtraining, mental fatigue and decreased training motivation.
One study showed that 16 weeks of training to failure resulted in lower testosterone and IGF-1 levels compared to a control group not training to failure.7
These hormonal effects could indicate non-functional overreaching, the undesirable form of training-induced overreaching.
Functional overreaching is when periods of training above normal intensity have a positive effect and lead to over-compensation and greater training adaptations.
Non-functional overreaching, on the other hand, is training with too high an intensity level over too long a time, leading to the athlete being incapable of proper recovery. This can have negative effects on performance, hormones and hypertrophy, and if left unchecked, can turn overreaching into real overtraining.
Save the Best for Last
Instead of taking every set of an exercise to concentric failure, it might be prudent to save the all-out effort to the last set. An athlete going to failure in the first few sets of an exercise might not be able to perform at an optimal level afterwards. This could negatively affect strength, force production, and muscle endurance. In turn, this performance decrease might lead to a lower total training volume, one of the major drivers of muscular hypertrophy.
Saving the set leading to failure for last, retaining the ability to perform a larger number of repetitions per set throughout the exercise could lead to a greater total training volume. This might be a good compromise between training volume, performance and still being able to reap any potential benefits of training to failure. This method also offers the feeling of accomplishment by having finished with an all-out effort.
A High Training Intensity Makes Failure Less Important
When using a relatively high load corresponding to an intensity of 6-12RM before reaching failure, research indicates that not training to failure will lead to a similar hypertrophic response as training to failure.
That high an intensity activates the motor units in the muscle fully, recruiting all muscle fibers immediately. This means that training to failure is not necessary to elicit a substantial anabolic response.
Studies on hypertrophy using high-repetition, low-load resistance training are rare. It seems likely that there is a need for training to failure, or at least very close to failure, to activate the same amount of motor units, thus creating the same stimulus for hypertrophy, when training with light to moderate weights.
Low load does not mean low effort, however. It is usual to experience sensations of discomfort and mental anguish when training to failure using loads allowing 20 to 30 repetitions. It is quite painful. Utilizing light weights and many repetitions is likely just as effective a driver of hypertrophy as training with a heavy load, as long as the sets are taken to failure, but it is not a pleasant way to train.
Trained and Untrained
The fact that the majority of the subjects in studies investigating the effects of training to failure are untrained is a significant limitation. This is often necessary to be able to see any significant effects of training interventions in a few weeks’ time, but it also makes it difficult to extrapolate the results to trained strength athletes and bodybuilders.
Athletes, who have adapted their muscles, central nervous system, and mental focus to high training volumes and high intensity over the course of years of hard training, might benefit from training to failure more often than someone who has just started training.
Compound Exercises Versus Isolation Exercises
Compound exercises, especially when performed with free weights, tax the muscles and the central nervous system far harder than isolation exercises using cables or machines. A free-weight training program based on compound movements like squats, deadlifts and bench presses, likely warrants limiting the number of sets taken to failure. If not, compromised recovery, leading to overreaching over time, is a potential consideration.
If the training program entails training to failure on a more regular basis, utilizing less demanding isolation exercises for that purpose might be a good compromise, allowing for both high intensity compound movements, training to failure, and proper recovery in one package. It is possible to train to failure more frequently without compromising recovery using isolation movements, as these are far less demanding.
Another reason to limit failure using heavy compound movements is the risk of injury. Coordination and stability could become an issue when training to failure on compound exercises. There is a large difference between failing on a set of heavy squats and failing on preacher curls. The former could easily lead to compromised form and risk of injury.
Training frequency also dictates the use of failure as part of a training program. Someone doing whole body workouts three or four times a week probably will not be able to train to failure very often, while someone splitting the body into numerous workouts over the week might very well be able to get away with it without impeding recovery, even with a high per-workout volume.
- Terminating a set a couple of repetitions before concentric failure is reached probably results in muscle growth and strength gains equal to or greater than taking it to failure.
- When using a moderate to heavy weight allowing 6–12 repetitions, training to failure probably offers few, if any, advantages.
- When using a lighter load, training to failure might be necessary to produce a substantial anabolic response.
- Training to failure should be limited when performing heavy compound movements using free weights.
- Training to failure can be utilized more often when performing isolation exercises without the risk of injury or overtraining.
- The higher the training frequency, the more restrictive the use of failure should be, to ensure proper recovery between training sessions.
- Muscle & Nerve, 03 January 2017. Clarity in reporting terminology and definitions of set endpoints in resistance training.
- Eur J Transl Myol. 2017 Jun 24; 27(2): 6339. Strength Training with Repetitions to Failure does not Provide Additional Strength and Muscle Hypertrophy Gains in Young Women.
- Sports Med. 37:225-264, 2007.The influence of frequency, intensity, volume and mode of strength training on whole muscle cross-sectional area in humans.
- J. Strength Cond Res. 28: 2775-2785, 2014. Blood ammonia and lactate as markers of muscle metabolites during leg press exercise.
- Sports Med. 2016 Apr;46(4):487-502. Effect of Training Leading to Repetition Failure on Muscular Strength: A Systematic Review and Meta-Analysis.
- Strength & Conditioning Journal: March 07, 2019. Does Training to Failure Maximize Muscle Hypertrophy?
- J Appl Physiol Vol. 100, No 5. 01 May 2006. Differential effects of strength training leading to failure versus not to failure on hormonal responses, strength, and muscle power gains.