It’s an age-old question for bodybuilders: “Do I go to failure on every set or do I leave some reps in the tank?”
Failure, which is also known Momentary Muscular Fatigue, occurs when you can no longer perform another rep with proper form. This forces you to stop or pause the set.
The concept of training to failure is certainly not new to bodybuilding. However, there is not one agreed-upon training system where training to failure is approached the same way.
In the early 1970s the notion of training to failure on every set was popularized by a number of well-known bodybuilders with the belief that training to the point of muscular failure was the necessary stimulus for maximum muscular growth. If you were performing an exercise with a weight that you could lift a maximum of 10 times, they believed that you would have to lift that weight for all 10 repetitions in order to maximally stimulate growth. Ending the set early meant that you were not giving maximal effort and therefore would not grow optimally. Since the 70’s entire training systems have been created about training to failure and more recently even “beyond” failure systems that incorporate forced reps and drop sets to get maximal effort from each training session.
"One thing both camps agree on is if you want to make gains, you need to work hard."
Others believe that training to failure is not only unnecessary, but it may be counterproductive to optimal recovery times and even catabolic. They believe that with heavier loads (4-6 rep max) you don’t need to train to failure because the load is heavy enough to recruit your largest motor units. Non-failure advocates will point out that outside of bodybuilding, other athletes like Powerlifters and Olympic Lifters seldom ever take sets to the point of failure and are able to build large, strong and muscular physiques as a result of heavy lifting.
One thing both camps agree on is if you want to make gains, you need to work hard. The question remains: is failure the definition of hard work? Should you train to failure, or not?
Well, the answer is not a simple yes or no, and in fact it’s probably a bit of both.
Pros of Training to Failure
Bodybuilders have been making gains for decades by taking sets to failure and there’s a reason. Motor unit recruitment is maximally recruited when training to failure. Simply put, a motor unit is your motor neuron and all the muscle fibers it innervates. The size principle of recruitment dictates that as training intensity increases, larger motor units containing fast twitch (Type 2) muscle fibers are progressively recruited to maintain the level of force to lift the weight.
This means, that the closer you train to the point of failure, the higher the number of fast twitch muscle fibers that are recruited (slow-twitch fibers because of their high fatigue resistance are recruited first), and it is these high-threshold fibers that have the most potential for growth in both size and strength. This simplification of muscle fiber recruitment patterns shows that by taking sets to failure you are exhausting more muscle fibers, in particular high growth potential muscle fibers, than if you stopped the set short of failure - and is strong support for the practice of training to the point of momentary muscular failure.
In a study published in 2007 in the Journal of Strength and Conditioning Research, researchers found that training to failure does in fact increase motor unit activation. It also found that it increased the secretion of muscle-building hormones, like HGH and testosterone.
Training to failure also heightens metabolic stress. Metabolic stress refers to the buildup of various metabolites like lactate and hydrogen ions which are thought to spur the muscle cell to grow. The mechanisms that contribute to muscle growth resulting from metabolic stress include increased fiber recruitment, elevated systemic hormonal production, alterations in local myokines, heightened production of reactive oxygen species, and cell swelling. This metabolic stress in the muscle signals adaptation, and can increase satellite cell activation as well as activation of the mTOR pathway, which in turn means increased protein synthesis and muscle size.
Cons of Training to Failure
On the other side of the coin, there is some evidence to indicate that training to failure on every set significantly increases resting levels of the catabolic hormone cortisol and suppresses anabolic growth factors . In one 2006 study led by Dr. Mikel Izquierdo it was demonstrated that training to failure increased resting levels of cortisol and suppressed IGF-1. This indicates that bodybuilders who take every set to absolute failure may be putting themselves at risk for slower recovery and less long-term muscle growth and strength gains.
Another study from 2012 found that training to failure increased nucleotide adenosine monophosphate (AMP). Elevated AMP indicates decreased mTOR signaling and protein synthesis.
Perhaps though, the biggest impact of training to failure is on the nervous system since training to failure can have a negative impact on the Central Nervous System (CNS) and the Peripheral Nervous System (PNS), the systems that control (contract) your muscles through electrical impulses.
Each neuron must release the neurotransmitter acetylcholine every time that it fires a motor unit, and this action is reliant on a number of substrates (including sodium, potassium and calcium) that engage in both the synthesis and breakdown of acetylcholine. As these substrates are depleted, the efficiency of the neuromuscular transmission decreases and eventually muscle contraction becomes weaker and slower, and at some point the nerve cell will actually assume a state of inhibition to protect itself from further stimuli. As such, overtrained or recently trained muscles require larger electrical impulses to initiate the same strong muscle contraction that a fresh muscle would require.
In the 1960’s a well-known doctor actually demonstrated this with a custom built machine called the Isotron. This machine was used to induce a muscular contraction using electrical impulses (not unlike a modern EMS machine). He discovered that a muscle that was recently trained required a much higher current to achieve a strong contraction.
The nervous system takes considerably longer than the muscles to recover from intense training. So by constantly going to muscle failure, it’s possible to overload this so much that it becomes impossible to train with a high frequency. In short, training too intensely, too often, will lead to nervous system inhibition, which leads to poor training sessions and sub-par training progress.
Train to Failure or Not?
As you can see, there are benefits and drawbacks to training to failure, but I think at this point you should be able to answer the question: “Should I train to failure?”
Answer: You should do both.
One simple way to approach this is to make training to failure simply an exercise-dependent variable. The more demanding an exercise is on the nervous system, the less often you should take it to failure. So for exercises like squats, deadlifts, free weight pressing or other “full body” compound movements and Olympic lifts, you should stop short of failure. Leave some in the tank, and complete another set. Stop each set when you start to lose form or when explosiveness and speed slows down.
However, in exercises where the nervous system is likely to be less taxed, like machine pressing, and chest, quad, hamstring, lower back, ab, calf and arm isolation work you should go to failure or even past failure on at least one set per exercise to maximize motor unit recruitment and metabolic stress. This is where you can employ advanced techniques like forced reps or drop sets.
If you think of training to failure as a tool that you bring out when the time calls for it, you’ll be able to reap the benefits and continue to make steady progress in both muscle size and strength.
1) Willardson JM. The application of training to failure in periodized multiple-set resistance exercise programs. J Strength Cond Res. 2007 May;21(2):628-31.
2) Izquierdo M, Ibanez J, Gonzalez-Badillo JJ, Hakkinen K, Ratamess NA, Kraemer WJ, French DN, Eslava J, Altadill A, Asiain X, Gorostiaga EM (2006) Differential effects of strength training leading to failure versus not to failure on hormonal responses, strength, and muscle power gains. J Appl Physiol (1985) 100:1647–56.
3) Gorostiaga EM, Navarro-Amezqueta I, Calbet JA, Hellsten Y, Cusso R, Guerrero M, Granados C, Gonzalez-Izal M, Ibanez J, & Izquierdo M. Energy metabolism during repeated sets of leg press exercise leading to failure or not. PloS One. 2012; 7(7): e40621.