Muscle failure is defined as reaching a point in a weight lifting set when you cannot execute another repetition.
This phenomenon can be achieved after five reps, 10 reps or may require 20 reps—it all depends on how heavy the weight is to the particular individual.
There are two kinds of muscle failure workout:
1. Mechanical Failure
This is when the weight simply becomes too heavy to lift any more, and occurs when the doable rep range is on the low side, such as a 6 RM with a barbell squat.
Mechanical failure does not hurt or burn much. It’s just that the weight eventually becomes too heavy to move, and the trainee must stop the set.
2. Metabolic Failure
This is the type that hurts or burns so much that the trainee is forced to stop, even though from a mechanical perspective, he or she is still capable of lifting the weight.
An example might be a set of incline barbell presses. The individual is able to complete 12 reps, but not without a lot of burning pain in the shoulders and even triceps, as fatigue increases.
Come rep #12, the trainee hurts so much that the set must end here, even though he or she knows that a few more reps could have been completed.
This type of training promotes more fat-burning than does mechanical failure.
Just because one reaches metabolic failure does not mean that maximal hypertrophy results will occur.
The pain can be deceiving and fool one into believing that optimal hypertrophy or strength gains will result.
With light enough dumbbells, one can perform this exercise for a 20 RM, but a 20 RM of this particular routine will hurt to high heaven. It’s just the nature of this exercise.
Another very painful exercise for higher-rep maxes is the leg extension, a single-joint (isolation) routine.
These absolutely kill when done to metabolic failure. But this doesn’t mean that the pain is an accurate gauge of intensity.
Muscle Failure And Workout Intensity Are Not One And The Same
One can achieve brutal pain with metabolic failure utilizing tension tubing for shoulder presses as low as 12 reps, yet this is nowhere near as intense a workout done with heavy dumbbells for a much less painful 7 RM.
Intensity is about progressive overload. Using heavier weights than in previous workouts, when possible, or increasing the number of reps over the last workout for a given exercise.
When those reps reach maybe 10 or 12, then using a heavier weight for a lower rep range, and then repeating the process.
Working with that weight till one reaches a higher rep range, and then using an even heavier weight.
This will force muscle growth, even though it is not the most painful way to lift weights.
In short, you need not be forced to crawl out of the gym after a leg workout, in order to experience a maximal-hypertrophy leg workout.
Someone once said, “If you can walk out of the gym after doing legs, get back in there!”
The implication is that a leg workout should be so torturous that the trainee can barely walk out of the gym. This is overkill and results from too many metabolic failure sets.
The legs are trashed and the trainee ends up very sore and stiff for up to several days after the session.
This kind of training is not seen in other training venues such as sprinting 100 meters or developing power at a tennis serve.
Sprinters do not keep running till they literally drop from pain (the equivalent of metabolic weight lifting failure). And tennis players do not keep serving till they can no longer even lift the racket over their head.
But when these athletes DO train, it is with a lot of power, speed and force: maximum effort over a short period of time for that given movement.
Nevertheless, there is a place for metabolic muscle failure exercises—not as a staple of the training regimen, but as an adjunct.
As part of a top program for building muscle, it’s important to hit as many muscle fibers as possible.
Maximum Muscle Fiber Usage
Taking a set to failure, whether it’s mechanical or metabolic, ensures that as many fibers are recruited as possible.
If you quit two or three reps short of what you’re capable of completing, muscle fibers will get missed.
However, doing your entire workout to failure is, as mentioned, overkill and will interfere with recovery.
Muscle failure exercises can be enhanced by employing drop-sets:
- Complete the first set to failure
- Immediately repeat the set with a lighter weight
- Immediately repeat again with an even lighter weight—all three sets to failure.
This will tap into as many muscle fibers as possible. Stopping at just the first set will hit the muscles hard, but think of all the fibers you’ll miss without the subsequent sets immediately after.
Drop-sets need to be done with discretion. Too many drop-sets can backfire by disrupting recovery and energy.
To learn more about the difference between intensity and muscle failure, and how to make muscle failure sets maximize your muscle-building goals, check out No-Nonsense Muscle Building Program by Vince DelMonte.
He goes in-depth about failure training as well as all sorts of other techniques for building lean muscle mass, with beginner and intermediate/advanced 29-week programs that change from week to week.
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