Training to Failure - Overtraining Prone & Useless? | Part 1/2 of a Research Update of 3 Popular 'Intensity Techniques'

No deadlifts in Nóbrega's training to failure study and + there are other issues w/ the "one-legged leg extension, only"-design.

Be honest, even though you may know that there's no convincing evidence of the superiority of training to failure, doing pyramid sets and/or drop-sets for increased size and strength your gut says: "Bro, that feels so damn challenging. It's got to work!"

That's not you? Well, I guess you will nevertheless be interested, whether the latest studies by Nóbrega et al. (training to failure | this part of the article) and Angleri et al. (pyramid and drop-sets | read about it in part 2 of the article) prove your gut feeling wrong, once and for all.
In this installment of this two-part review we will start with the never-ending debate about training to failure. A technique of which a 2007 review by Willardson et al. says that it "might provide the extra stimulus needed for advanced lifters to break through plateaus" (Willardson. 20017). Against that background, it appears to be logical that a cursory read of the literature suggests that there is a sign. number of studies to confirm that 'training to failure is more anabolic than shying away from failure'. A closer read of the corresponding studies, however, indicates that the hypertrophy and/or strength advantages many papers respond could well be the mere effect of an increased training volume. How's that and why's that relevant? Well, if one group of subjects stopped after 8 reps while the other did another 1-2 rep/s on almost every set, that's a 10-20% increased workout volume, which, in turn, is one of the few variables with sufficient scientific evidence that it facilitates skeletal muscle hypertrophy (Schoenfeld. 2010 & 2013).

Against that background, the results Sanmy R. Nóbrega and colleagues present in their soon-to-be-published paper in Journal of Strength and Conditioning Research are all-the-more surprising. After all, their study design did not equate the volume in the four groups of untrained young men (age: 23.0 ± 3.6 years; height: 176.0 ± 0.6 cm; BMI: 24.3 ± 3.9 kg/m²) who participated in 12x2 workouts per week over the course of the 12-week experiment:

• HIRT-F and HIRT-V: Three sets of unilateral (=single leg) leg extensions at 80% of the individuals' 1-RM twice a week performed to failure (HIRT-F) or the point where the subjects stopped voluntarily (HIRT-V), respectively
• LIRT-F and LIRT-V: Three sets of unilateral (=single leg) leg extensions at 30% of the individuals' 1-RM twice a week performed to failure (LIRT-F) or the point where the subjects stopped voluntarily (LIRT-V), respectively

What the study did do, unfortunately, is to use single-leg leg extensions to allow for four study groups with only 30 subjects by having each subject train his two legs differently - one to failure another to volitional interruption. And that's a problem...

Figure 1: Maximal dynamic strength (1-RM) and muscle cross-sectional area (CSA) at baseline (Pre) after 6 (6W) and 12 weeks; *Significant difference compared to Pre; †Significant difference compared to 6W (Nóbrega. 2017)

Why's that a problem? Well, while there is no conclusive evidence that training one leg will have the other grow, as well, there are at least a good dozen of ways training one leg to failure could have affected the adaptive response in the other leg that have not been convincingly disproven, yet. Catoire et al. (2012) have observed sign. gene changes, for example, in both the trained and untrained legs, Fimland, et al. (2009) and similarly Kannus et al. (1992) report that neural adaptations lead to strength gains in the untrained leg, and Munn et al. (2004) conclude in their meta-analysis that "[p]oling of all available data shows that unilateral strength training produces modest increases in contralateral strength" - 7.8%, a strength increase that's small, but could be pronounced enough to mask an inter-group difference in the study at hand. Not to mention difference according to the muscle group you train and the exercise you do (doing only leg-extensions is not exactly all-encompassing and obviously does not allow for reliable conclusions about the effects on e.g. hamstrings, glutes, triceps, biceps, chest, and doing the corresponding exercises to failure or not).

Figure 2: Effect of unilateral resistance training on the strength of the contralateral limb (Munn. 2004); last paragraph of the conclusion of Munn's meta-analysis (inset in the lower right corner).

And that's not the only methodological characteristic of the study at hand that refutes the initially alluded to hypothesis that it would provide "proof" that training to failure doesn't add to the exercise-induced increases in strength and hypertrophy. Another, caveat that's at least as relevant is the lack of training experience of the thirty-two subjects - there's, after all, a good reason scientists love untrained subjects: they will see impressive gains, (almost) no matter what they do. The impressive responsiveness of newbie-muscles to any muscle-building stimulus alone could thus have masked an inter-group difference and thus the benefits of training to failure... which brings us back to the initially cited statement from the conclusion of Willardson's 2007 review: "Training to failure might provide the extra stimulus needed for advanced lifters to break through plateaus" - do you notice something? Yes, Willardson et al. were careful or precise enough to highlight who will benefit from training to failure, i.e. "advanced lifters".

And there's more. The scientists from the Eastern Illinois University also highlight that this intensity technique should be "incorporated periodically into short-term microcycles". Eventually, the question whether you should train to failure or not may thus be reduced to the question of when in your macrocycle will you have microcyles (4-6 weeks) of training to failure, but that's a topic for a completely different article.
References:

• Catoire, Milène, et al. "Pronounced effects of acute endurance exercise on gene expression in resting and exercising human skeletal muscle." PloS one 7.11 (2012): e51066.
• Fimland, Marius S., et al. "Neural adaptations underlying cross-education after unilateral strength training." European journal of applied physiology 107.6 (2009): 723.
• Izquierdo, Mikel, et al. "Differential effects of strength training leading to failure versus not to failure on hormonal responses, strength, and muscle power gains." Journal of Applied Physiology 100.5 (2006): 1647-1656.
• Kannus, P., et al. "Effect of one-legged exercise on the strength, power and endurance of the contralateral leg." European journal of applied physiology and occupational physiology 64.2 (1992): 117-126.
• Munn, Joanne, Robert D. Herbert, and Simon C. Gandevia. "Contralateral effects of unilateral resistance training: a meta-analysis." Journal of Applied Physiology 96.5 (2004): 1861-1866.
• Nóbrega, Sanmy R., et al. "Effect Of Resistance Training To Muscle Failure Versus Volitional Interruption At High-And Low-Intensities On Muscle Mass And Strength." The Journal of Strength & Conditioning Research (2017).
• Schoenfeld, Brad J. "The mechanisms of muscle hypertrophy and their application to resistance training." The Journal of Strength & Conditioning Research 24.10 (2010): 2857-2872.
• Schoenfeld, Brad J. "Potential mechanisms for a role of metabolic stress in hypertrophic adaptations to resistance training." Sports medicine 43.3 (2013): 179-194.
• Stone, Michael H., et al. "Training to Muscular Failure: Is It Necessary?." Strength & Conditioning Journal 18.3 (1996): 44-48.
• Willardson, Jeffrey M. "The application of training to failure in periodized multiple-set resistance exercise programs." The Journal of Strength & Conditioning Research 21.2 (2007): 628-631.