In this Q&A I’m going to address a few common questions about training to momentary muscular failure (MMF); what it is, whether it is necessary, and if it’s more effective to train past it.
What is momentary muscular failure?
Your muscles fail when fatigue has momentarily reduced their strength to below the level required to continue an exercise in the prescribed form.
When performing typical dynamic exercise protocols your muscles fail when you are unable to continue positive movement (positive failure). When performing yielding isometric protocols like static holds your muscles fail when you are unable to hold the weight motionless preventing negative movement (static failure). When performing negative-only your muscles fail when you are unable to lower the weight as slowly as prescribed (negative failure).
Is it necessary to train to momentary muscular failure?
No. It is not necessary to train to MMF to stimulate improvements in muscular strength and size or other aspects of functional ability, you just have to consistently work your muscles harder than you did previously. However, since results from exercise are proportional to intensity of effort, you should train to MMF.
Exercise intensity is best defined as how hard you are working relative to your momentary ability. If at the beginning of an exercise your muscles are capable of producing one hundred pounds of force but you are only working against a resistance of eighty pounds your intensity is eighty percent. As your muscles fatigue over the course of an exercise the eighty pounds of resistance requires an increasing percentage of your decreasing momentary strength. When your strength has been reduced to just below eighty pounds all of your momentary strength will be required to just hold the resistance and you will be working at one hundred percent intensity.
With most equipment it is impossible to know your exact strength or intensity of effort at the beginning of or at any point during an exercise (and both one rep maximum and max effort isometric testing should be avoided for safety). The only time you know how intensely you are working is when you reach MMF, at which point your intensity is maximum.
Is it better to train past momentary muscular failure?
Yes, but only very briefly.
When performing normal dynamic repetitions the only way to be certain you have achieved MMF is to continue attempting to move positively for a few seconds. Occasionally when you think you have achieved MMF if you attempt to gradually contract harder you will find you are able to continue positive movement. You may only move a few more degrees or inches, or you may end up completing another repetition. There is no way to be sure you have achieved positive failure unless you keep trying for at least a few seconds. However, beyond some point additional contraction post-failure appears to be counterproductive. Advanced trainees who routinely perform extended static holds, multiple forced reps, or multiple rest-pause reps beyond failure often find they require a much longer time to recover between workouts. A little seems to go a long way, and it is very easy to overdo or misuse these techniques.
Some of these have uses when training beginners who are still learning to train with a very high level of intensity, but only very few, and they need to be done correctly and used very judiciously or they will not have the desired effect.
For most people I recommend only continuing to contract for about five seconds after positive movement stops. If you’re really contracting as hard as you can and the weight doesn’t move after five seconds you’re probably not going to move it, and you should just slowly lower it and unload.
When performing static holds, once you are unable to maintain the prescribed position you should slowly lower the weight, unload, and terminate the set. If you used an appropriate load and time additional reps are unnecessary and potentially counterproductive. I recommend a conservative range of around sixty to ninety seconds.
When performing negative-only repetitions you should unload and terminate the set when you are unable to perform the negative at least slowly enough to maintain a ten-second cadence. Never attempt to continue a negative-only set beyond this point.