Failure, a Necessary Prerequisite for Max. Muscle Growth & Strength Gains? Another Study Says "No Need to Fail, Bro!"

To Fail or not to fail, the answer is... according to the latest 12-week study "not to fail", well at least the there was no significant difference between the size and strength gains of the subjects in a recent Australian study. On the other hand, who knows if the same is true for other muscle groups than the biceps and/or better-trained subjects?

If you've been following the majority of the past ~2,000 SuppVersity articles the headline of today's SuppVersity article which gives away the main result of a recent study from the University of Wollongong in New Southwales, Australia (Sampson. 2015) should not surprise you.

After all, the study at hand is by far not the first one to challenge the broscientific "wisdom" that you'd have "to fail to succeed". On the other hand, researchers like Burd et al. (2010) or Mitchell et al. (2012), for example, found that resistance exercise performed to failure elevates muscle protein synthesis independent of volume (sets × reps) or % one repetition maximum (1RM) load. Results that would have us assume that failure, not the total work, the rep numbers and what not was the major determinant of skeletal muscle hypertrophy.
To find out whether that's actually the case and whether and why the use of other training methods yield similar or inferior gains, J. A. Sampson and H. Groeller conducted a study in which they compared the effects of 4 weeks of biceps training with

• non-failure rapid shortening (RS; rapid concentric, 2 s eccentric), 
• non-failure stretch-shortening (SSC; rapid concentric, rapid eccentric), and 
• failure control (C, 2 s concentric, 2 s eccentric)

in a 12-week study in twenty-eight males who completed a 4-week familiarization period and were then counterbalanced on the basis of responsiveness to the aforementioned groups.
All trainees, irrespective of the group they'd been randomized to trained thrice a week using 85% of their individual one repetition maximum (1RM). Next to the muscle size that was measured as cross-setional area of the muscle (CSA), the scientists also assessed the individual 1RMs (strength), the maximal voluntary contraction (MVC) and the muscle activation (EMGRMS) of the agonist, antagonist, and stabilizer muscles before and after the 12-week training period.

Figure 1: There were no significant inter-group differences in favor of or against training to failure (Sampson. 2015).

As the data in Figure 1 shows, the average number of repetitions per set was significantly lower in
RS 4.2 [confidence interval (CI): 4.2, 4.3] and SSC 4.2 (CI: 4.2, 4.3) compared with C 6.1 (CI: 5.8, 6.4). The increases in 1RM (30.5%), MVC (13.3%), CSA (11.4%), and agonist EMGRMS (22.1%), however, did not differ between groups.

Only the activity of the antogonist, in this case the triceps brachii different with significantly higher increases in triceps activity in the SSC and the C trial, but decreased activity in the RS trial.
References:

• Burd, Nicholas A., et al. "Low-load high volume resistance exercise stimulates muscle protein synthesis more than high-load low volume resistance exercise in young men." PloS one 5.8 (2010): e12033.
• Mitchell, Cameron J., et al. "Resistance exercise load does not determine training-mediated hypertrophic gains in young men." Journal of applied physiology 113.1 (2012): 71-77.
• Sampson, J.A, and H. Groeller. "Is repetition failure critical for the development of muscle hypertrophy and strength?" Scand J Med Sci Sports (2015): Ahead of print.