Training to failure is more likely to mean frying your CNS which has a bigger impact on your training, health, recovery and is not conducive to sensible training.
This should not be confused with time under tension which is a useful and proven aspect of building muscle.
When it comes to both the central and peripheral nervous systems training to failure is not recommended for muscle growth or even strength training (to an extent - i.e. pushing 1RMs once a cycle is fine, doing it every session - no.)
As your muscle fibers tire and start to fail or imminently fail your CNS recruits all available motor units it can and tries to fire them as much as it can. However, as your maximum contraction continues the frequency of which your CNS fires at it maximum potential decreases and the level at which it fires decreases in general.
I won't bore you with the sodium/potassium transport pathway for ATP, or the synthesis and breakdown of acetylcholine (ACh), but it is an interesting read which should help you understand how each neuron must release acetylcholine (ACh) (a neurotransmitter), every time it is triggered of fires a motor unit. The short end of it is, as these substrates are exhausted (potassium/sdoium cycle etc...) failure starts to approach we still use max effort to lift the weight, so it isn't a liner relationship. Overtrained or recently trained muscles require a much higher current than a rested muscle for strong contractions to be achieved - if you don't get a strong contraction, your body isn't able to fire ACh correctly, or enough.
Since as you approach failure, or you have been training hard, a larger signal is required to actually complete a contraction of the same size as a recovered and rested muscle. So by training to just before failure will still create the microtrauma in your muscle fibres without draining the CNS (well actually the PNS (peripheral nervous system)).
As we know your CNS works by sending lots of tiny electrical impulses across your body via nerves to the the muscle or motor unit you're wanting to move. Believe it or not the transmission of these signals can't actually be sustained for long period with speed and power for the optimum frequency - hence why we can't sprint for more than a relatively short distance. Going back to the sodium/potassium cycle and other substrates, as their concentrations decrease, your body gets to the point where these contractions become weaker, more laborious and as we have all experienced a lot slower (that grinding last rep!!!!). Pus hard enough, and you end up in a state of inhibition. This basically prevents any further stimulus - i.e. your body will just not physically be able to move in that manner, that is pure exhaustion.
A lot of research is still being done about this, but your mood and mental state can have a profound effect on your CNS - which is why a lot of people concentrate, psyche themselves out a get themselves "in the zone" before doing some big lifts.. obviously you can still over train doing this so you have to be aware of not doing 1RMs all the time - or pushing yourself that hard every session. If you do decide to train to failure each time you train you are going to set your nerve cells into what is basically a constant state of inhibition - this will lead you to effectively "fry" your CNS far too much - and I use the word "fry" quite purposefully as this will be by way of an increased output of electrical impulses - excessive electricity = burn out!. So this basically leads to over training, as I mentioned right at the top of my post this will lead to you wanting to take some time off, you might get fluy, and your mental states becomes pretty low/negative as such you end up lacking motivation, appetite, and your hormonal balance will be completely a kilter etc.... However more importantly it can potentially mean that you're not also getting any muscular failure, which is exactly the opposite of what you're after, if you fry your CNS it means you're not working your muscles efficiently or enough and owing to your time off and lack of motivation, you will take 2 steps back and one forward. You end up gaining NOTHING every time you train this way. Adding your muscular AND neuro failure, you end up training badly, with poor form since you're not able to activate everything properly, which means you may injure yourself and have to take EVEN MORE time off... something to think about, you end up not putting on muscle, get skinnier and weaker and have to take time off...
So... muscular failure, it doesn't matter if it is concentric, eccentric or isometric or anything -tric is just not needed if you want to build muscle and get stronger.
What you DO need however, is:
1) Good form
2) continuous training (even if you're not making immediate progress it is better than pushing yourself 100% all the time)
3) build up of fatigue (this is fine, as long as it is not over training(
4) good diet
5) Good rest/sleep/recovery.
Your muscles do need enough training stimulus for micro tears (or microtrauma) in your muscle fibres to happen (this causes your body's regenerative cycle to kick in, builds more muscle to repair the damaged ones). This will aslo trigger intracellular calcium levels to rise as a result this will bring an onsite of both growth and detoxifying processes (e.g. reduction of lactic acid for one) but wiuthout caning your CNS.
Your CNS is a vital part of your training but caning it all the time will be detrimental in the long term.
). So if i feel well oiled and strong i'll go for a workout where i can concentrate and lift heavy, often to failure.