It seems that hitting momentary mechanical failure is equally if not more important tan the load you lift.
^^ A good study looking at 3x Fail x30% VS 3x Fail x80%.
In short, the act of hitting failure provide adequate stimulus to trigger muscle growth.
The growth was essentially the same in both groups, however the group that used a heavier weight got stronger as well (pretty logical).
So what does this mean for your training?
You can look at it one of two ways:
1 – Cycle your loads between 30-80% 1RM and perform 3 sets per muscle group to muscle failure each set (after a couple of warm up sets, obviously).
2 – You can take this data and combine to s strength program to add some extra oomph, so perhaps performing working sets at a standard weight, say 5x5x80% (leaving reps in the take and focusing on strength), followed by a back off set of the same weight or between the 30-80% mark for AMRAP to hit failure, triggering more growth stimulus.
Both options are viable, both will improve strength and size.
Another nice option is this:
W/U – 10-15 reps
Set 1 – 10 reps – tough
Set 2 – 8 reps – tougher
Set 3 – 6-8 reps – hardest set
Set 4 – reps to failure with previous load or reduce load by 20%
If you ever see someone who has any decent amount of size you’ll notice they’ve often blended training to failure with stopping just short, try it yourself and see how you do.