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What is Muscular Failure: The Weight Room Part 2

DeLorme Definition of Muscular Failure

Continuing from Part 1 where I looked at the concept of muscular/task failure in general, Part 2 of what is rapidly becoming an overwritten series began looking at what muscular failure represents in the weight room specifically.    There I defined different muscle actions and types of muscular failure noting that I’d be focusing on concentric muscular failure.  I also looked at the concept of the sticking point and how it impacts on all of this.

In this part I want to continue that discussion and look at some of the actual definitions of muscular failure that have been used in the weight room over the decades.  As importantly I’ll look at what the implications of each might be in both a practical and research sense.    However, as promised in Part 2, I want to start by looking at the concept of the Repetition Maximum or RM.

Repetition Maximums (RMs)

The concept of the Repetition Maximum or RM is similar but not truly synonymous with that of muscular failure, even if many (incorrectly) use the terms interchangeably.    Reaching muscular failure refers to not being able to complete the task.  For now let’s just use that to mean not being able to complete a full range repetition.  The RM is the maximum number of repetitions that were actually completed.  An example may make this easier:

You’re doing barbell curls with 100 lbs.  You are able to complete 12 full range repetitions and then fail to complete the 13th repetition.  We would say that you failed on repetition 13.    However, this weight would represent a 12RM.

By definition, the RM will always be one repetition less than the repetition number where actual failure occurred.

Note that any RM value can be defined.  A 1RM is the maximum weight you can lift once where failure would occur on repetition 2.   A 3RM is the maximum weight you could lift three times with failure occurring on the fourth.    A 10RM is the maximum weight you could lift 10 times with failure occurring on the eleventh.

Let me also note that the RM concept assumes a maximal effort on the part of the trainee.    If someone lifts a weight once when they could have lifted it 3 times it’s not a 1RM just because they stopped at 1 rep.  If someone lifts a weight once but could have lifted more weight once (failing on repetition 2) that’s not an RM either.

The RM weight is the maximum weight you can lift for a given number of repetitions where muscular failure would occur on the next repetition.

Pedantic Pedantry

As I mentioned above, it’s not uncommon for people to use RM and failure synonymously even if that’s not completely accurate.   And I guess there is a slight logic to it.  If you did 12 repetitions and couldn’t have gotten the 13th repetition, the 12th rep is kind of the failure rep.  Or rather you might say you did 12 reps to failure.

In a practical sense it certainly doesn’t matter a lot.  Mind you, this presumes that you wouldn’t have gotten the 13 repetition to begin with which I’ll come back to.

But in the most literal sense, the RM should always be 1 rep less than the rep where muscular failure actually occurs.  The maximum number of reps you could do was 12 and you either did fail or would have failed on 13.

As one researcher puts it (MF is muscular failure)

“The difference between the RM and the point of MF is that the RM means that the set is terminated after the final repetition has been completed [authors’ emphasis] in good form… whereas the point of MF means that once the RM has been reached another repetition is attempted [authors’ emphasis] but not completed. Therefore the last repetition is the failed repetition.”

Basically, assuming a true RM load, muscular failure should occur at RM + 1 repetition.  If a set was a true 12RM, the 13th rep would be failure.  As above, this is a bit of pedantry and you will see the terms used somewhat interchangeably.  It’s not technically accurate but clearly the difference is small in the big picture.

Determining RM

Before moving on I want to address a problem with RM which is how it should be determined.  As I said above, the strictest definition of an xRM is the ability to do x reps but not x+1 reps.   Let’s use x=10 so the writing isn’t as horrible.  How do you know you could only do 10 reps but not 11?

In the very very strictest sense the only way to know if you could only do 10 reps but not 11 would be to attempt that 11th repetition.  That is to take the set to actual muscular failure.    This raises the issue of constantly training to actual failure and whether that’s good, bad or indifferent, but that’s not the topic of this series.  But, again, the only way to truly know if the weight is a 10RM is to attempt the 11th repetition and actually fail to complete it.

Another way would be to test the 10RM at some point in training (or a study) and then assume the weight used will remain a 10RM.  So let’s say at the start of a study or training program you determine that 100 lbs is your true 10RM (i.e. you actually attempt the 11th repetition and fail to complete it).  This might be a reasonable assumption over some time period but if strength gains are occurring what was a 10RM weight before may not be anymore.

Note: I know that tools such as Reps in Reserve (RIR) and Reps to Failure (RTF) exist for exactly this reason.  I’ll discuss those in what will now hopefully be Part 5 of this rapidly expanding series.

But in the vein of RIR and RTF there is the concept of the self-determined RM.  In this case the trainee simply assumes that they have reached their RMThat is, they decide when they think that they will be unable to complete another repetition (i.e. they predict that they would reach failure on the following repetition).  So if they reach 10 repetitions and feel that they wouldn’t complete an 11th, that is a self-determined RM.

In an RIR/RTF framework this would represent an RIR/RTF of 0.  But this is fundamentally based on the trainee’s ability to accurately gauge when true muscular failure will occur.  This gets into a lot of issues with trainee’s relative ability (or inability) to do this accurately.  Again, later in this article series.

The Only True RM is a True RM

Ultimately the only way to truly know if a weight is an RM load is to attempt the next repetition until failure actually occurs.    Yes, fine, if you’re highly trained you might know.  A good coach can probably tell you based on what they are seeing without going to actual failure.   But in the strictest sense, unless the next repetition is attempted and failure occurs, the set can’t be said to have been a true RM.

Which brings me finally to the different definitions of failure, what they represent, along with what implications each might have for describing/comparing training programs or research studies.

Definitions of Failure

As I’ve endlessly reiterated, the problem with simply referring to “training to failure” is that a variety of definitions have been used over the years and they are far from identical.  For a good historical look at this I recommend a paper titled Clarity in Reporting Terminology of Set End Points in Resistance Training by James Steele et al.     It also provides suggestions for a more consistent set of definitions for use in research that you can read for yourself.  I’ve presented those below.

Fisher et al. Terminology for Set Termination

So let me now go through some of the different definitions, in either concept or specific description, what they represent and what implications their use might have for training or research.

Physiological Muscular Failure

As I described in Part 1, physiological muscular failure refers to a situation where a muscle’s force output can no longer meet the force requirement of the activity.  In Part 2, I described how, in the weight room, this will generally mean an inability to lift a weight through the sticking point as that is where the maximum force requirements will occur.

This might better be described as being unable to lift a weight through a full range of motion and this is reasonably easy to define.  If someone is doing barbell curls and cannot go from full extension (arms straight) to full flexion, they have reached muscular failure.   Once again, most likely they will fail to get the weight through the middle of the movement.

In a squat, this would be defined as the inability to get from the lowest position of the squat to full lockout at the top.  The same would go for the bench press or leg press.  In a pulldown or rowing movement, it’s a little bit hazier but an inability to get the bar to touch the chest on a pulldown or handle to touch the stomach would fairly well define failure.

Certainly this is a good definition and fairly easy to define.  But it still doesn’t quite capture the nuance of when failure might be defined in the weight room.

Does Form Matter?

For example, we might let this definition include performing any number of repetitions through a full range of motion no matter what they look like.  That is, however the repetition is done is fair game.

Lift your hips off the bench when you’re bench pressing or bounce it off your chest?  Great.  Lean all the way back on biceps curls to get the rep?  Fantastic.   Use a ton of body English to get the row handle to touch your stomach, great.

Hell, in a lateral raise, just dip down as you throw the DB’s up.    Not only can you claim a full range of motion since the weights technically went above your shoulders, you can also take advantage of relativistic training principles.

It should be fairly clear that using such a vaguely defined endpoint isn’t very useful.   If the point of all my blathering is to address the idea of muscular failure in terms of its impact on the target muscle and hypertrophy, allowing anything to be fair game technically misses the point.

If someone continues to get more repetitions of a biceps curl by leaning back to get through the middle, that doesn’t mean anything in terms of actual muscular biceps failure anymore than bouncing a bar off the chest in the bench press does.

As I’ve discussed, a lighter weight lifted properly might actually be a GREATER stimulus for growth than a heavier weight lifted with poor form.  The goal as always is sufficient muscular tension on the target muscle. And depending on the situation, allowing form to break can actually reduce that muscular tension since everything but the target muscle is now helping to get complete the lift.

And one of the most commonly added riders/qualifiers to the general definition of failure can be summed up by DeLorme’s (look it up, kids) original definition of an RM load.

DeLorme Definition of Muscular Failure

The bolded bit is the key here as we’ve now added the rider of performing the lift correctly (i.e. with proper technique).  Most call this form failure and that’s what I’ll spend the rest of today on.

Form Failure

While there are other qualifiers that may be added to the definition of failure, the criteria of using proper form is arguably one of the most commonly seen and this is commonly referred to as form failure.  The definition is used repeatedly throughout the strength training literature and appears often in research studies.

Certainly including proper form as a qualifier for determining an RM load or muscular failure is a good one since it eliminates getting reps “by any means possible”.  But it also raises a staggering number of issues.  Because now we get to argue about what actually constitutes form failure and how it can be objectively defined.

Because among other issues, how we might define form failure will depend on the exercise being done to begin with.

Form Failure on Compound Free Weight Movements

First let’s look at compound free weight multi-joint exercises since that is not only what a majority of studies use but also where the big problems are going to show up so far as I’m concerned.

What would form failure represent on a squat?  A lot of things potentially.  Cutting depth would be one definition and certainly lifters do that as they fatigue.  But at what point do we objectively say that depth has been cut too much for the repetition to count.  Some studies at least describe setting and enforcing depth.  I’d love to see the videos.   An Instagram video I can’t currently find had the lifter squat to a box and that standardized depth.

What if the lifter starts to tip forwards or shoot their hips?  Is that form failure?  What if they were already using a squat form that was based around hip drive (ahem)?  In that case is form failure actually squatting properly without hip drive?   Is it a different definition if the initial repetitions are bolt upright and then they start to tip a bit?  How much tip is allowed before we declare form to have broken?

Do we define it by an inability to keep a hard arch in the upper back?  Or lower back?   At what point do we objectively say “This is form failure” and stop the set?  At what point do you consider technique to be deviated enough from “proper” to call form failure?

What about the bench press, how are we defining form failure?  Does it occur when the lifter starts to lift their butt off the bench?  Is it their head coming up?  Is it a deteriorating bar path?    Is the lifter starting to bounce the bar off their chest? If the study was using a touch and go bench, how bad does the bounce have to be before the set is stopped.

And studies using the deadlift?  Good god….The number of places you could potentially define form failure is enormous here.  Seriously, researchers, don’t even pretend you have lifters taking deadlifts to failure.

All of which is compounded by the fact that studies don’t seem to define “Form failure” to begin with.

For example, in the original volume paper that kicked all this nonsense off, Schoenfeld et al. use the following definition

Sets consisted of 8 to 12 repetitions carried out to the point of momentary concentric failure, that is, the inability to perform another concentric repetition while maintaining proper form.

This is fine in that it defines momentary failure as an inability to maintain proper form.    But the only description of form comes in the section on testing 1RM where squat depth and a 5-point contact on bench press are described.  Which is at least something I guess.

Interestingly, a very recent paper actually did explicitly define form failure during sets of squats stating:

Repetition failure was operationally defined as the inability to complete a repetition, or an observable change in technical execution increasing injury risk (e.g., spinal flexion, valgus collapse, asymmetry, and imbalance) [].

Valgus collapse is knees breaking in, by the way.   And while this does allow for somewhat of a judgement call (i.e. how much knee break in is allowed) it’s still better than most in terms of specifically defining form failure.

And if a study is going to use form failure as a definition, it needs to be clearly defined.

What Muscle is Failing?

Louie Simmons once wrote that “movements don’t fail, muscles do.”  By that he meant that a missed lift was ultimately determined by whichever muscle was unable to generate sufficient force to meet the requirements of the movement.

It’s just the old “A chain is only as strong as the weakest” link principle.   If every muscle in your body can squat 600 lbs but your low back can only handle 500 lbs, you can only squat 500 lbs.  Essentially.  If you bring your low back strength up to where it can handle 650 lbs, you can still only squat 600 lbs because all of the 600 lb muscles are now limiting.

And this brings up an issue of critical relevance to the topic of actual muscular failure and the idea of how we track training volume for a target muscle in terms of growth. And yes, this is the same point I’ve brought up multiple times but it bears repeating.

Let’s say we have someone doing squats “to form failure”.   Whether failure has been defined specifically or not, we always have to ask what muscle failed?  That is, what muscle or muscles were responsible for the inability to complete the repetition in good form?

If the low back rounding is defined as failure and that means the set is stopped, what does that tell us about how close to failure the quads did or didn’t get?   It tells us nothing is what it tells us.  This can even vary by individual.  Someone with long femurs who squats very bent over will fatigue at the low back faster than someone who can sit bolt upright.  This matters.

If someone’s low back is very limiting, it might hit failure many many many repetitions before the quads are anywhere close to actual muscular physiological failure.   So say your quads could actually do 200 lbsX14RM while the low back is limited to 200lbsX10RM.

At rep 10, the low back fails, the set is stopped and the quads are still 4 reps from failure.  Counting that as a “set to failure” is only correct for the low back in this case.  The quads were nowhere close.  In the effective reps framework, the low back probably got 4-5 effective reps but the quads only got 1.

I’d refer readers back to the previous part of this series for a more detailed discussion.

Technical Competency in Compound Movements

Importantly to this part of the series, the use of form failure for compound movements then interacts with the trainee’s level of experience and technical competency.  Let’s say I was training a beginner on squats and defined muscular failure as “form failure”.  I mean, I’d never have a beginner squat to failure in the first place but let’s say I was.

Anybody who has trained anybody knows that a beginner’s form will break very early on because it’s not stable to begin with.  Does that break in form tell us anything about the stimulus that their quadriceps experienced?  Of course not.

And yes this is a bit of a silly example, just to make a point.  That point being that the relative degree of technical competency in a complex movement has a profound impact on how similar “form failure” and “physiological muscular failure in the target muscle” will be.

As people become more well trained, presumably their technique becomes more stable.  Which means that presumably they are likely to get closer to actual muscular failure in the target muscles before their form breaks.     And the example above is silly because the studies at issue here used “trained” individuals.

Here’s the Thing

But here’s the thing.  I’ve been in gyms for 35 years total and 25 of those professionally and the number of high quality technical squatters I can remember seeing I can count on maybe 4 hands.  And I personally trained at least 2 hands worth of those.

That’s people who were training for years and years.  And squatting badly for all of them.     I’ve had trainees with 20 years experience who had to start completely over technically because everything they did was wrong.  Training age per se says nothing about anything.

And the number of trainees I’ve ever seen who can get anywhere close to actual muscular failure in their quads before their form breaks are few and far between.  I’ve simply watched too many people squat over the past 2-3 decades to believe that your average college student,  regardless of training experience is going to get close to muscular failure before their form breaks on a complex movement.

Most people in most gyms have shit squat form to begin with.  It’s just a statement of fact.  Don’t tell me the average person in a college exercise physiology class has not only good technique but sufficient technical stability to get close to physiological muscular failure in their quads before their form breaks (there’s another issue here that I’ll address later).

Researchers are happy to prove me wrong by taking video of the workouts rather than making excuses on why they can’t.  Show me what failure in squats and bench press looked like in your studies so I can see how close any of the trainees got to actual muscular failure.

Your phone has a camera and everybody is on Instagram.    The videos don’t need to be reviewed (this was the excuse Brad gave for why he can’t video the workouts because it’s easier to make excuses then step up your game).    It’s time to put up or shut up.

Because as I’ve said for nearly 18 months now, I don’t believe for a goddamn second that anybody did 5X8-12RM to form failure in the squat with a 90 second rest or 8X10RM to form failure on 60 seconds with anything approximating quality of training.

Show me the fucking video if you want to prove me wrong.  Or just admit I’m right.

The Consequences of Using Form Failure in Compound Movements

But the upshot of this is that a set of squats taken to “form failure” is likely to be far removed from anything approximating true muscular failure in the sense of force production being below force requirements at the sticking point.   And only the latter is of any real relevance to whether or not the set was a training stimulus or not.

I don’t give a damn if you hit “form failure” on back squats due to your low back giving out if my goal is to train your quads or measure quad growth in response to different training volumes.  A 10RM defined by your low back strength/endurance tells me nothing about how close to physiological failure your quadriceps were.  If your low back gave out when your quads had 5 more reps in them then that set was, physiologically, a warm-up set for your quads.  Of course you’ll need 45 sets per week but only because the sets are useless.

Then we get into the issue of what muscles are being used in different parts of the movement.  Squats involve glutes, quads, low back, upper back and more.   When “failure” of any sort occurs, how can we really say what’s failing to begin with in most cases?   And when a study is only measuring a single muscle group for size changes, this matters.

If you fail on bench off the chest, what failed?  Was it pecs, deltoid, serratus, triceps?  This matters when the study is measuring triceps size changes.

Let’s not even talk about deadlifts.

At best it might represent a limiting muscle hitting failure but that says nothing about the other muscles that are involved.  If your low back hits “muscular failure” in the squat which throws off your technique, there’s no way to tell how close your quads were to actual muscular failure. Or your glutes.

And when you start to think about that in terms of the idea of effective reps, maybe you see what I’m getting at.  Let’s say you’ve been given a workout of, for example 5 sets 8-12 RM of squats to form failure on a 90 second rest interval.

Related: How Should I Set Rest Intervals in the Weight Room?

And let’s say that your low back gives out on rep 10 of the set and your form breaks so the set is stopped.  You did a set of 10RM to form failure.  But what if your quads still had plenty left?  What if they could have generated sufficient force for 14 reps?

Well your quads weren’t anywhere close to muscular failure.  They didn’t reach full recruitment and the number of “effective reps” per set suddenly dropped.  Because instead of getting 3-4 effective reps you only got one.  Suddenly you need 3 times as many sets to get a quad stimulus.

And this will get worse as more sets are done on a short rest interval.  Because as fatigue accumulates, form failure is going to start occurring sooner and sooner.  And if it was the low back that gave out initially, it’s going to give out sooner and sooner with each subsequent set.  Which means that the quads are likely to be that much further from failure (yes, I know, fatigue will accumulate.

Because if you’re measuring quad size changes what matters is the stimulus your quads actually got.   Not how many sets of essentially sub-maximal, relative to the quads, sets of squats you did.  And counting sets doesn’t tell you that per se.  You need to know what training stimulus the quadriceps got.

And having what are only moderately trained individuals who are unlikely to have great technical stability perform a complex compound exercise to “form failure” is not going to tell you that under most circumstances.  It’s simply not.

But there is a way around it.

Form Failure on Machine/Isolation Movements

But what about machine or isolation movements?  Here the issue is much less complicated.  Because on a machine, form is much more controlled and constrained and form failure is far more likely to represent true muscular failure.

I mean, on a leg press, what form is there to break exactly?   Not lowering the sled enough is the usual culprit, people start cutting depth.    Knees can break in to be sure.   It’s still vastly less of an issue compared to a squat.

But on a leg extension?  What is form failure?  Yes, fine sometimes you see some goofy shit but it’s rare and limited.  On a leg extension form failure should represent physiological muscular failure in the sense of being unable to complete the movement through a full range of motion. Or at least be a damn sight closer to it than on a squat.

And here set counting is likely to be much more accurate in the sense that it represents the muscle in question actually being trained closer to actual muscular failure.  You still have the issue of compound machine movements where multiple muscles are working and the muscle that is limiting may or may or not be what’s being measured for size changes.

But it at least takes out the variable of how technical the movement is and how stable the technique of your subjects are.  Because if they are like the trainees I’ve seen for 25+ years in the gym, I can say without hesitation that their form is breaking on squats  or bench press long before they are getting anywhere close to true physiological muscular failure in terms of force production relative to force requirements.  Ok fine, some muscle is unable to keep up but there’s zero guarantee that it’s the one muscle researcher seem intent on measuring.

Whereas I bet I can take one of them to true failure on a leg press or leg extension and get a hell of a lot closer to failure.  Where doing Ultrasound on the quadriceps might actually now be meaningful in determining a dose-response relationship of volume to growth.

A Thought

And perhaps that would be an interesting experiment for someone to actually do: do a volume comparison study with nothing but machine and/or isolation movements.    It’s not without precedent.

Yes, look, I realize that squats, bench press, etc. are often chosen since they “are commonly included in weight training programs” and that’s fine.  But baseline research doesn’t always have to be completely ecological in this regard.

A study that used compound machine movements would more or less eliminate the issues with form failure I brought up.  Yes, fine, people can still do goofy shit, usually squirreling around in a machine or whatever.  But compared to all of the different ways form can break in a squat or bench press, what people do on a chest press machine or what have you doesn’t even begin to compare.

But here sets “form failure” are going to be a hell of a lot closer to physiological muscular failure than in a study using squats or bench press.   There’s no bar path to deviate on a Hammer incline press.   You either get it through the sticking point to lock out or you don’t.

Of course, compound exercises still don’t address the issue of what muscle is failing in a given movement.

That could be addressed by doing nothing but isolation work.  No, it’s not how most train (although I bet more would benefit from it in a hypertrophy sense).  But if a study did 8 sets of 10RM on a pec deck with a 2′ rest interval and then actually measured pec growth or 8 sets of triceps pushdowns and then measured triceps growth, it would tell us a hell of a lot more about optimal volumes than doing 15 sets of barbell bench press “to form failure” and then measuring the triceps.

It’s just a thought but what do I know? I don’t even do science.  Even if I seem to be able to come up with better designs than most of what is in this field.  Anyhow.

And while I’m actually not done, this is where I’m cutting it today.  I’ll continue looking at issues of muscular failure in the weight room next time which should hopefully finish up the discussion of definitions of muscular failure in the weight room and how they can impact on practice and research.  Then, some video demonstrations to make my real point.

Read What is Muscular Failure: The Weight Room Part 3

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