Cut and Paste because I didn't want to link to another forum.
This is not a anti failure post by any means, I use it myself at times. However there are some that think that taking a set to the point of momentary muscular failure is necessary to force the muscle to adapt through hypertrophy. Is this belief accurate?
Muscle doesn't know 'failure'
Muscle doesn't know 'a set'
It's only us in our minds that realize failure and plan out bio-mechanical work (muscle contractions) into organized structures called 'sets'
All muscle is capable of is:
1/ Producing bio-mechanical force.
2/ Inducing metabolic fatigue.
3/ Work induced micro trauma.
It doesn't matter if a lifter performs one set to failure or multi sets not to failure, so long there is enough bio-mechanical work to cause enough micro trauma to the muscle fibers, and metabolic fatigue to produce sarcoplasmic hypertrophy, then there will be increase in both size and strength.
Failure is merely an event not a stimulus for hypertrophy, it simply means that within that set you've reached a point of fatigue where the muscle is no longer able to produce a force greater than that of the load on the bar.
Some overly dogmatic advocates on failure training would say then at the point of failure you've done ALL you can to stimulate hypertrophy, this is inaccurate, lighten the load and you'll perform a few more reps, rest/pause 20 seconds and you'll get more reps, allow someone to spot you and you'll get a few more reps. These techniques allows you to perform even more bio-mechanical work than just stopping at failure, so clearly failure is not the point where you have done all you can possibly can within a set.
However there can be a problem with using these extra intensity set extending techniques. You are essentially redlining your CNS (central nervous system) and causing neural fatigue and likely for many progress comes to a quick and abrupt halt.
Solution, well as we've established, there is no 'magic switch' that turns on at failure, and failure is merely an event due to fatigue and not a magic hypertrophy stimulus or switch, therefore it makes sense to induce more bio-mechanical work, fatigue and micro trauma through muscle fiber contraction using a multiple set approach while staying 1-2 reps shy of failure.
That's not to say that failure should always be avoided, for some, low volume failure-rest/pause training works great, these are usually advanced lifters that have built up the CNS capacity to be able to generate great intensity and to be able to recover, but even then such training is usually periodized and deloads used to allow accumulated fatigue to dissipate. For most lifters in my opinion failure should be used as a tool, not the rule.
There is one point I must not over look regarding failure, failure can be an effective tool for enhancing neural strength adaptions due to the fact that at failure, similar to a 1 rep max, you are exerting maximum available force. So failure is a useful tool for enhancing neural efficiency.
The point here is that failure is not the only, or even optimal stimulus... So what is?
I'd like to repeat/highlight an important point:
So long there is enough bio-mechanical work to cause enough micro trauma, and metabolic fatigue to produce sarcoplasmic hypertrophy, then there will be increase in both size and strength provided that volume, intensity and frequency are effectively managed.
This is best served by either an increase in volume with the same load, an increase in load with the same volume, or a combination of volume/load increase. These equal THE answer for the stimulus of continued strength and hypertrophy - Simple and basic progression!
Some claim that workload is not the stimulus for strength/hypertrophy, this is also not quite accurate, the only reason that ANY program works is because there must be SOME workload, failure can be avoided and progression made, however no workload equals no progression.
Summary
1/ Failure is an event not a magic switch or THE hypertrophy stimulus.
2/ Failure increases neural strength and efficiency.
3/ In my opinion failure should be used as a tool not a rule (unless following a program specifically based on failure)
4/ There's no magic in failure, muscle doesn't know failure, only we do.
5/ Simply keep progressing and increasing workload (add weight and/or reps)
Manipulating the various set/rep schemes that are commonly used is useful in putting together a program based on our goals