Training To Failure: The Good, The Bad And The Reasons
Years ago Arthur Jones said that training to the point of muscular failure was the necessary stimulus for optimum muscular supercompensation. Mike Mentzer was (still is) absolutely adament about it, repeatedly stating that if the muscle isn't pushed to the point of momentary concentric failure then no supercompensation will be stimulated. Bill Pearl holds the conviction that one should NOT train to the point of failure. Top Powerlifters seldom train to failure. Olympic Lifters rarely ever take sets to the point of failure. Note: By failure here I mean momentary concentric failure, i.e. the inability to complete another full repetition of the concentric phase of the lift (you could, however, continue to do static holds and negatives). Some people advocate doing negative only sets to the point of momentary eccentric failure (the inability to complete another full repetition of the eccentric phase of the lift - you are unable to stop the bar from crashing down on you).
So, is there a way of determining which of these methods have merit (without actually trying them all - possibly wasting a lot of time and even risking injury)? Yes, of course there is. If you haven't read the Neuromuscular System series and the article entitled Muscular Fatigue During Weight Training on the 'Physiology Related Articles' page, then I suggest that now would be a good time to have a look at them. A great deal of the knowledge that you need to analyze all of the above weight training approaches is there. Let's have a look at those approaches with the experience of others and muscle physiology in mind.
Training to Failure: Necessary or Not?
As I stated above, some high intensity training advocates have stated, point blank, that if you don't train to momentary concentric muscular failure then you will not grow. That's a pretty bold statement. The logic goes like this:
Your body responds to demands that you place on it. If you don't take your sets to failure, then the message your body gets is that it is already strong enough to perform the tasks being required of it (lifting that particular weight for the number of sets and reps that you performed). Similarly, in order for your body to respond by getting stronger and bigger, you must attempt the momentarily impossible, and take your reps to failure. This will send a clear signal to your body that it is presently insufficiently equipped to do the tasks that it is being presented with and your muscles will, therefore, adapt and grow/get stronger.
The logic seems bullet-proof. But you really don't have to look very far to dispell it. Top Powerlifters, Olympic-stlye Weightlifters and many Bodybuilders rarely, if ever, train to momentary concentric muscular failure, yet I probably don't have to tell you that they haven't had a problem with realizing muscular growth and/or strength increases. I recall reading an article by Ed Coan from about ten years ago in which he stated that he never went to failure on any of his sets. Bill Pearl says the same thing. "But they were on steroids", some of you will say. Well, of course they were. But most pre-steroid era bodybuilders didn't train to failure and they never had a problem with muscular growth either. "But they weren't that big" some more of you will say. That's precisely because they weren't on steroids. As most people can appreciate, the drug-bloated addicts that are now presented as bodybuilders have raised people's definition of 'heavily-muscled' to the point where any man less than 250 lbs. with 4% bodyfat is small and fat. If you really think that men such as George Eiferman, John Grimek and Steve Reeves weren't that big, maybe you should see them standing next to 'normal' men, or in more normal circumstances than oiled up on a posing dias. Take a look http://web.archive.org/web/200411130...e-steroid.html. If that doesn't convince you, compare your own overhead lifts to what the Olympic Lifters were doing years before the advent of steroids. 180 pound Weightlifters were routinely pressing well over 300 pounds overhead in the early 1950s! The level of strength that these men posessed was developed without steroids and without training to failure. The success of these people in building muscle, power and strength while not training to failure proves that such training is not necessary (at the very least, for some) to realize muscular conditioning and growth.
So now the question is clearly not whether training to momentary concentric failure is absolutely necessary (it may not be for you), but whether it is the most effective way to weight train.
Training To Failure: The Most Effective Way To Weight Train?
Physiologically, we need to consider what happens when a weight training movement is taken to failure. Muscles fail because they're firing patterns can no longer provide them with enough sufficiently rested fibers in order to continue to produce the necessary force. Taking a segment from the article The Neuromuscular System Part I: What A Weight Trainer Needs To Know About Muscle:
Muscle Fibers have two recruitment patterns. In the first pattern, units that innervate the same types of fibers are recruited at different times, so that some units are resting (recovering) while others are firing. Obviously, at high loads this pattern isn't possible because all available motor units will have to be fired at the same time to lift the load. In the second pattern, motor units that are more fatigue resistant are recruited before fibers that are more rapidly fatigued.
Since productive (not rehabilitative) weight training involves lifting weights that require the firing of the type I, IIA and type IIB fibers, the highest threshold fibers will cause failure when they fatigue. What I mean is that if you lift a load that requires the participation of the high threshold type IIB fibers, then this weight could not be lifted without them (although they may not develop their maximum tension by twitching at maximum frequency). If it could have been, the type IIBs would not have been recruited at all. When these fibers fatigue you can, therefore, no longer continue to lift the weight. And remember, even if the weight isn't initially heavy enough to recruit the highest threshold fibers, as the lower threshold fibers fatigue the higher threshold ones are gradually recruited to take up the slack. Oh yeah, the highest threshold fibers also happen to be the ones with the most potential for growth. So, by taking the set to failure you are exhausting more of these muscle fibers than if you stopped the set short of failure. Strong support for taking sets to the point of momentary concentric failure, if fiber exhaustion is indeed the stimulus for growth.
Muscle Fiber Considerations
So, what exactly is muscle fiber exhaustion? The causative factors of muscle fiber fatigue were covered extensively in the Muscular Fatigue During Weight Training article and somewhat in the Neuromuscular System series on the 'Physiology Related Articles' page. Taking some information from those sources we have:
From the phosphagen system:
Declining intramuscular ATP is thought to be a major cause of fatigue during high intensity exercise.
Creatine phosphate (CP) concentrations quickly decrease within the first few seconds of exercise and eventually decreasing to 5-10% of the pre-exercise concentration within 30 seconds. When this happens there is insufficient CP levels to replenish ATP stores at an optimal rate.
As contraction continues, there is not enough CP left to continue fueling the ADP -> ATP conversion and ATP stores get depleted also. This, along with the influence of some other occurances, brings a cease to muscular contraction.
And during the anaerobic glycolysis mechanism:
Lactic acid build-up in the muscle cells make the interior of the muscle more acidic. This acidic environment interferes with the chemical processes that expose actin cross-bridging sites and permit cross-bridging. It also interferes with ATP formation. So, these factors, along with depleted energy stores, cause the muscle fibers to become fatigued and contraction to cease.
...during muscle contraction, calcium ions (Ca++) are released from the sarcoplasmic reticulum by way of the T System and then returned to that organelle by way of the Ca-Pump. What would happen then, if all this didn't go as smoothly as anticipated?
Studies on isolated muscle fibers have, indeed, linked reduced sarcoplasmic Ca++ concentrations to fatigue. Specifically, repetitive 'tetanic' contractions of isolated muscles caused a gradual decline of force that was closely associated with a decline in sarcoplasmic Ca++ concentrations (Westerblad & Allen, 1991). After only 10-20 such contractions, sarcoplasmic calcium concentrations became insufficient for forceful contraction (Westerblad et al., 1991). The reason for this is simply because decreased Ca++ release for binding to troponin reduces the number of actin/myosin cross-bridges that can be formed.
Forceful contraction could be reestablished with extremely high doses of caffeine (which stimulates greater Ca++ release from the sarcoplasmic reticulum), but this required caffeine doses at physiologically dangerous levels. This does show, however, that the problem appears not to be with the Ca++ concentrations in the sarcoplasmic reticulum, or their release channels, but probably as a consequence of impaired T-tubule signaling. During repeated contractions of a muscle fiber, K+ begins 'pooling' in the T-tubules. This results from an inability of the Na+/K+ ATPase Pump to maintain the proper Na+/K+ balance on the sarcolemma (at the T-tubules). This disturbance of the membrane potential in the T-tubules inhibits the conduction of the action potential to the sarcoplasmic reticulum and Ca++ is not optimally released - and, thus, forceful contraction is not achieved.
In addition, lactic acid build-up factors in here also. Increased intracellular H+ concentrations (caused by lactic acid accumulation) slows the uptake of Ca++ by the sarcoplasmic reticulum. This occurs because H+ interferes with the operation of the Ca++/ATPase Pump. This reduces muscle contraction force by interfering with intracellular and sarcoplasmic reticulum Ca++ concentrations.
As ATP is broken down to provide energy for muscular contraction inorganic phosphate (Pi) accumulates in the cell. On the one hand this is 'good' because phosphate (Pi) is known to be an important stimulator of glycolysis (the breakdown of glucose to produce ATP) and glycogenolysis (the breakdown of glycogen to produce ATP) - thus stimulating the production of more ATP by these pathways. But the increased Pi levels also inhibit further cross-bridges from being formed between actin and myosin filaments. When ATP is used to fuel contraction Pi must be released from the myosin head. Elevated intracellular Pi concentrations impairs this process, resulting in reduced tension development - meaning that as Pi builds up, muscular force production goes down. This may be another contributing factor to muscle fatigue.
There's nothing magical in any of the above that implies that momentary muscular failure, itself, directly causes a subsequent increase in muscular strength/size. It may be possible that a lower blood pH (caused by the high muscular concentrations of lactic acid) causes growth hormone (GH) release which may, in turn, have anabolic effects - but only if several other factors are also in line. Anecdotal evidence, however, points out that growth hormone per se is not the major player when it comes to muscular growth/strengthening. When judging the merits of training to failure, though, this effect must be taken into account. This whole argument, of course, only applies if you are performing weight training with weights that cause the predominant utilization of the anaerobic glycolysis mechanism (weights that cause failure to occur in ~30 to ~60 seconds of beginning the set - around 75% to 85% of your 1 rep maximum - the bodybuilding mainstay).
If you've read the articles on this site about muscular growth you will, however, know that the build-up of phosphate and hydrogen ions as a muscle fatigues is thought to contribute to the growth stimulus. It is only logical to conclude that training to failure would result in a larger accumulation of these metabolites and, therefore, produce a greater growth response. But if these fatigue factors were the most potent stimulus for growth then Bodybuilding techniques such as compound sets, and drop sets (which create great fatigue in the muscles) would be known as the most powerful tools for promoting growth. Yet years of experience of thousands of Bodybuilders have shown that this is not necessarily the case - compounds sets, for sure, are considered to be used more for 'detailing' and 'refining' muscular development.
Still, it cannot be denied that these fatigue metabolites have their role in promoting muscle growth. But would two sets, not to failure, produce the same, or greater, result as one all-out set? Maybe. Maybe not. Other factors have yet to be considered.
From the perspective of tension and time: Since it is clear that muscles grow in response to tension and the time that they are required to produce this tension (resulting in microtrauma being done to the fibers), anything that prolongs the time under which they are contracting hard will also increase the growth stimulus. In this light, training to failure is definitely more efficient at stimulating muscular gains than stopping short of failure. The amount of time that the last failure rep extends a set has to be considered. If you did nine full reps in a set, reaching failure on the tenth rep and assuming that the tenth rep (which was only partially completed) lasted the same duration as the other reps (which it may or may not), then attempting that tenth rep extended the set ~10% longer than if you had stopped at the ninth rep. From only the perspective of time under muscular tension, which is a strong stimulus for muscular adaptation, training to failure is more efficient at stimulating muscular growth and strengthening than stopping sets short of failure.
A note on negatives: Research has shown that negatives (eccentrics) produce more microtrauma to muscle fibers than concentrics or isometrics. This occurs not only because of complex biomechanical processes but also because fewer total fibers are recruited during the eccentric portion of a lift than during the concentric phase (the lifting part). Fewer fibers doing the job mean more tension is developed in each fiber and, therefore, more damage is sustained by each individual fiber. Recent studies have indicated that this does not necessarily translate into accelerated growth, though. As was covered in the articles on The WeighTrainer about muscular growth, muscle damage and muscle recovery and supercompensation are different processes. High levels of microtrauma (as caused by strong eccentric contractions) are known to interfere with glycogen replenishment and other metabolic processes in muscle after training - this may factor in. Before you decide to try to minimize the negative portions of your lifts, however, bear in mind that many other studies have indicated that the negative phase is, in fact, the most important phase of the lift for stimulating hypertrophy (growth). The lesson to be learned is that negative-accentuated training will stimulate growth - perhaps moreso than any other type of training - but because of the level of damage they do, and the resultant disruption of metabolic processes such as glycogen replenishment, negative-emphasis reps will impose a longer recovery period.
Peripheral Nervous System Considerations
Getting back on subject: It was covered in the Neuromuscular System series that contracting a muscle involves more than just what occurs in the muscle itself. The nervous system is intimately involved in the process. Taking another few lines from that series:
...as effort fractionally increases, so does the frequency of firing of each motor unit. A sudden increase in force requirement is met by the recruitment of more motor units.
So, extending this, as the muscle fibers exhaust, and you reach the point of failure, the nervous system will recruit all available motor units and fire them as frequently as is possible. It is a well-established fact, though, that as a maximum muscular contraction continues, the frequency of motor units firing decreases. In fact, one study showed that by the end of a 30 second maximum voluntary contraction the firing frequency decreased by 80%. Eventually the frequency of twitching of the high threshold fibers becomes insufficient to sustain the effort.
We know that each neuron must release the neurotransmitter acetylcholine (ACh) every time that it fires (or 'twitches') a motor unit. We also know that the neurons transmit impulses down the length of their axons by way of Sodium/Potassium transport and the Sodium/Potassium ATPase Pump. The signal is carried across the membrane of the muscle cell in the same manner. The whole process also relies heavily on optimum calcium levels and enzymes that are involved in the synthesis and breakdown of acetylcholine and numerous other substances. The frequency of motor unit firing decreases, therefore, as these substrates are exhausted - yet as failure approaches we continue our maximal effort to lift the weight. What kind of an impact does such a furious effort have on the nervous system?
Consideration of such matters really is nothing new, but it probably is to most weight trainers. Consider the fact that during the 1960s a man called Dr. John Ziegler designed a machine that he used to monitor overtraining by sending electric currents through muscle. The 'Isotron', as he called it (cheesy 60s name), would be used to induce a muscular contraction by supplying a small electrical impulse to the muscle being tested. It was found that an overtrained or recently trained muscle would require a higher current than a rested muscle for 'strong' contraction to be achieved. What does this tell us? It tells us that for a period after training a higher than normal activation threshold is needed to produce contraction.
Incidently, ~75 mA was the 'normal' current required to produce 'strong' contraction. Anything over ~100 mA was considered indicative of overtraining. You may also be wondering how accurate this is given the fact that type II fibers naturally have higher activation thresholds than type Is. Well, oddly enough, when it comes to external stimulation (such as the kind the Isotron applied) the type II fibers are actually easier to induce a contraction in than the type Is.
Regardless of all this - and whether signal transmission at the neuron or sarcolemma is responsible for the effects - this clearly illustrates that the peripheral nervous system requires its own recovery period after training!
In addition, from the Muscular Fatigue During Weight Training article:
There is evidence that fatigue during fast and powerful activities (such as some forms of weight training) occurs first at the neuromuscular junction. This would mean that failure during such an activity occurs not because of muscle fiber factors, but because of an inability on the part of the nervous system to innervate the muscle cells optimally. Precisely, the motor neurons cannot manufacture and release acetylcholine (ACh) fast enough to maintain transmission of the action potential from the motor neurons to the muscles.
This is another way in which failure can occur because of the peripheral nervous system.
Central Nervous System Considerations
Our nervous system arguments up to now have focused on the peripheral nervous system. But, as any experienced coach can tell you, the central nervous system has a large bearing on the failure point and the overtraining phenomenon. Taking another segment from the Muscular Fatigue During Weight Training article:
In order for a muscle fiber to twitch the central nervous system (CNS) must send a nerve impulse to the controlling motor unit. The innervating nerve cannot maintain its capacity to transmit this signal, with optimum frequency, speed and power for extended periods of time. Eventually concentrations of substrates such as sodium, potassium, calcium, neurotransmitters, enzymes, etc. decreases to the point where muscle contraction becomes markedly slower and weaker. If high discharge rates are continued the nerve cell will assume a state of inhibition to protect itself from further stimuli. The force of contraction, therefore, is directly related to the frequency, speed and power of the electrical 'signal' sent by the CNS.
Interestingly, though far from understood, is the fact that a trainee's motivation and emotional state can profoundly affect the discharge characteristics of the central nervous system.
Clearly, the central nervous system can play a pivotal role in the perception and reality of fatigue.
If these concepts seem a bit vague, just think of a lifter 'psyching up' for a big lift, or remember some time when you thought that you couldn't possibly get another rep, but somehow managed to 'dig deep' and force another one out. Both of those situations illustrate the manipulation of the central nervous system in order to allow the lifter to be stronger. Any experienced coach will tell you, however, that you shouldn't 'psyche up' all the time or you'll 'burn yourself out'. The 'old-timers' referred to this as using up too much 'nervous energy'. However you want to look at it, training too intensely, too often, will certainly lead to the nerve cells entering a state of inhibition. When that happens you can forget about making good progress until you take enough of a break to allow for central nervous system recovery.
NOTE: As a general rule, training to failure with low reps and heavy weights is much more taxing on the nervous system than training to failure with high reps and lighter weights. Keep this in mind when you're designing your training programs.
So, for heavy training, failure may not even occur because of exhaustion of the muscles at all, but because of exhaustion of the nervous system, so to speak. This would, assumably, take a large 'recovery' toll on the nervous system.
Special Considerations For The Olympic Lifts (and closely related lifts)
As anyone who practices these lifts knows, they are extremely complex, high-skill movements. Because of the very explosive nature of these lifts, the very fastest-twitch fibers must be recruited during their execution if the lifts are to be performed properly. Higher reps would require the use of training weights that would not be heavy enough to maximally stimulate these high threshold fibers - the ones that are used for the all-important maximum single attempts. For these reasons, Olympic lifters practice, almost exclusively, low reps on these style lifts. For an Olympic lifter, performing higher reps just wouldn't be a sensible training practice. All this means that the nervous system takes quite a beating on these lifts. Pertaining to failure (again from the Muscular Fatigue During Weight Training article) remember:
There is evidence that fatigue during fast and powerful activities (such as some forms of weight training) occurs first at the neuromuscular junction. This would mean that failure during such an activity occurs not because of muscular failure, but because of an inability on the part of the nervous system to innervate the muscle cells.
Combine this with the fact that muscular and neuromuscular fatigue quickly causes a deterioration of form on these complex lifts, and you have a strong case against taking sets of the Weightlifting-style lifts to failure. In fact, it is very rare for Olympic weightlifters to train the Olympic lifts to failure (unless, of course, they miss a maximum attempt); it just makes no sense.
For someone who wishes to practice these lifts (or, more likely, their 'power' versions) for strength development or athletic improvement, it still doesn't make sense to practice higher reps, as the very nature of these lifts require activation of the fastest of the fast twitch fibers. These fibers are, by nature, quickly fatigued. Don't forget that even the simpler 'power' versions of these lifts (the Power Clean, Power Jerk, Power Snatch), or even High Pulls, still qualify as high-skill movements and, therefore, are susceptible to form deterioration with fatigue. Slightly higher reps than with the full Olympic lifts may be employed though - up to 5 reps - but they should not be trained to failure.
What Really Makes A Muscle Grow And Strengthen
If you've read the Muscle Growth series, combined with what was discussed above, it's probably becoming obvious to you by now that training to muscular failure (concentrically, eccentrically or isometrically) is NOT the necessary stimulus for growth. Quite simply, tension, time and the build-up of fatigue products is. The fibers need to develop sufficient tension for long enough a period to damage themselves (incur microtrauma) - causing growth factors to be released in the cells and leached out into the surrounding area and intracellular calcium levels must rise to 'set off' both growth and destructive processes. Extra growth stimulus is also provided by the build-up of fatigue metabolites such as phosphate and hydrogen ions (caused by elevated lactic acid levels). None of this is dependent on reaching a point of momentary failure. In fact, depending on rep-range and overall training volume, the failure effort may prove to be an 'unreasonable' burden on the nervous (both central and peripheral) and signaling systems (primarily the T system). Time must then be given for the recovery and supercompensation processes to take place.
This isn't to say that training to failure can't have a place in a sensible training schedule, as it certainly can and, in fact, does. For people who possess above average nervous system recovery abilities it may even become a major mainstay of their training programs. The point is simply that the effects of such training and personal recovery patterns of all systems involved have to be considered before such a training approach is adopted.
I really hope this article has helped you sort out some of the confusion that surrounds the "you have to train to failure to make a muscle grow" mentality. By now, you should be seeing that those 'boring' physiology articles really do have a purpose.