Where are these studies that have disproven that training to failure is not required? I'd like to see them. Anyways, the whole key is to find a training method that allows one to make continuos progress ie. allowing PROGRESSIVE OVERLOAD to work it's magic 
And for me, that method was described in my previous post.
i agree progressive overload is key 100%.
regarding not training to failure:
Differential effects of strength training leading to failure versus not to failure on hormonal responses, strength, and muscle power gains
The purpose of this study was to examine the efficacy of 11 wk of resistance training to failure vs. nonfailure, followed by an identical 5-wk peaking period of maximal strength and power training for both groups as well as to examine the underlying physiological changes in basal circulating anabolic and catabolic hormones. Forty-two physically active men were matched and then randomly assigned to either a training to failure (RF; n = 14), nonfailure (NRF; n = 15), or control groups (C; n = 13). Muscular and power testing and blood draws to determine basal hormonal concentrations were conducted before the initiation of training (T0), after 6 wk of training (T1), after 11 wk of training (T2), and after 16 wk of training (T3). Both RF and NRF resulted in similar gains in 1-repetition maximum bench press (23 and 23%) and parallel squat (22 and 23%), muscle power output of the arm (27 and 28%) and leg extensor muscles (26 and 29%), and maximal number of repetitions performed during parallel squat (66 and 69%). RF group experienced larger gains in the maximal number of repetitions performed during the bench press. The peaking phase (T2 to T3) after NRF resulted in larger gains in muscle power output of the lower extremities, whereas after RF it resulted in larger gains in the maximal number of repetitions performed during the bench press. Strength training leading to RF resulted in reductions in resting concentrations of IGF-1 and elevations in IGFBP-3, whereas NRF resulted in reduced resting cortisol concentrations and an elevation in resting serum total testosterone concentration. This investigation demonstrated a potential beneficial stimulus of NRF for improving strength and power, especially during the subsequent peaking training period, whereas performing sets to failure resulted in greater gains in local muscular endurance. Elevation in IGFBP-3 after resistance training may have been compensatory to accommodate the reduction in IGF-1 to preserve IGF availability.
Concurrent Endurance and Strength Training Not to Failure Optimizes Performance Gains
Purpose: The purpose of this study was to examine the efficacy
of 8 wk of resistance training to failure versus not to failure training regimens at both moderate and low volumes for increasing upperbody
strength and power as well as cardiovascular parameters into a combined resistance and endurance periodized training scheme.
Methods: Forty-three trained male rowers were matched and then randomly assigned to four groups that performed the same endurance
training but differed on their resistance training regimen: four exercises leading to repetition failure (4RF; n = 14), four exercises not
leading to failure (4NRF; n = 15), two exercises not to failure (2NRF; n = 6), and control group (C; n =
. One-repetition maximum
strength and maximal muscle power output during prone bench pull (BP), average power during a 20-min all-out row test (W20min),
average row power output eliciting a blood lactate concentration of 4 mmolILj1 (W4mmolILj1), and power output in 10 maximal strokes
(W10strokes) were assessed before and after 8 wk of periodized training. Results: 4NRF group experienced larger gains in one-repetition
maximum strength and muscle power output (4.6% and 6.4%, respectively) in BP compared with both 4RF (2.1% and j1.2%) and
2NRF (0.6% and j0.6%). 4NRF and 2NRF groups experienced larger gains in W10strokes (3.6% and 5%) and in W20min (7.6% and 9%)
compared with those found after 4RF (j0.1% and 4.6%), whereas no significant differences between groups were observed in the
magnitude of changes in W4mmolILj1 (4NRF = 6.2%, 4RF = 5.3%, 2NRF = 6.8%, and C = 4.5%). Conclusions: An 8-wk linear
periodized concurrent strength and endurance training program using a moderate number of repetitions not to failure (4NRF group)
provides a favorable environment for achieving greater enhancements in strength, muscle power, and rowing performance when
compared with higher training volumes of repetitions to failure in experienced highly trained rowers.
Fatigue is not a necessary stimulus for strength gains during resistance training.
Folland JP, Irish CS, Roberts JC, Tarr JE, Jones DA.
Chelsea School Research Centre, University of Brighton, Eastbourne, UK. j.folland@bton.ac.uk
Abstract
BACKGROUND: High resistance training enhances muscular strength, and recent work has suggested an important role for metabolite accumulation in this process.
OBJECTIVE: To investigate the role of fatigue and metabolite accumulation in strength gains by comparing highly fatiguing and non-fatiguing isotonic training protocols.
METHODS: Twenty three healthy adults (18-29 years of age; eight women) were assigned to either a high fatigue protocol (HF: four sets of 10 repetitions with 30 seconds rest between sets) to maximise metabolic stress or a low fatigue protocol (LF: 40 repetitions with 30 seconds between each repetition) to minimise changes. Subjects lifted on average 73% of their 1 repetition maximum through the full range of knee extension with both legs, three times a week. Quadriceps isometric strength of each leg was measured at a knee joint angle of 1.57 rad (90 degrees ), and a Cybex 340 isokinetic dynamometer was used to measure the angle-torque and torque-velocity relations of the non-dominant leg.
RESULTS: At the mid-point of the training, the HF group had 50% greater gains in isometric strength, although this was not significant (4.5 weeks: HF, 13.3 (4.4)%; LF, 8.9 (3.6)%). This rate of increase was not sustained by the HF group, and after nine weeks of training all the strength measurements showed similar improvements for both groups (isometric strength: HF, 18.2 (3.9)%; LF, 14.5 (4.0)%). The strength gains were limited to the longer muscle lengths despite training over the full range of movement.
CONCLUSIONS: Fatigue and metabolite accumulation do not appear to be critical stimuli for strength gain, and resistance training can be effective without the severe discomfort and acute physical effort associated with fatiguing contractions.
Fatigue contributes to the strength training stimulus.
Rooney KJ, Herbert RD, Balnave RJ.
School of Physiotherapy, University of Sydney, Australia.
Abstract
To investigate the role of fatigue in strength training, strength increases produced by a training protocol in which subjects rested between contractions were compared with those produced when subjects did not rest. Forty-two healthy subjects were randomly allocated to either a no-rest group, a rest group, or a control group. Subjects in the two training groups trained their elbow flexor muscles by lifting a 6RM weight 6-10 times on 3 d each week for 6 wk. Subjects in the no-rest group performed repeated lifts without resting, whereas subjects in the rest group rested for 30 s between lifts. Both training groups performed the same number of lifts at the same relative intensity. The control group did not train. Subjects who trained without rests experienced significantly greater mean increases in dynamic strength (56.3% +/- 6.8% (SD)) than subjects who trained with rests (41.2% +/- 6.6%), and both training groups experienced significantly greater mean increases in dynamic strength than the control group (19.7% +/- 6.6%). It was concluded that greater short-term strength increases are achieved when subjects are required to lift training weights without resting. These findings suggest that processes associated with fatigue contribute to the strength training stimulus.
in short studies show that failure is a endurance/energy demand not a muscular tension demand. i.e. the muscle mostly fails because of a lack of atp/glycogen in the muscle or basic fatigue, not because the fibres have worn down/been worked too hard etc
load is the key.
