Evidence in Favor of Low Load Pre-Exhaustion to Failure for Increased Strength & Size Gains from Recent Study

Unfortunately, the study involved doing only one exercise - leg extensions.
As a SuppVersity reader you will have heard about all sorts of intensity techniques in various of the hitherto published 1,800 articles, but convincing evidence that dropsets, pump sets or, as in the study at hand, pre-exhaustion techniques are effective means to improve the strength and size gains in response to standardized resistance training regimen is scarce.

Andreo Fernando Aguiar and his colleagues from the North University of Paraná (UNOPAR) and the Londrina State University (UEL) in Brazil obviously knew this, when they came up with the simple, yet effective design for their latest 8-week study.
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In short, the scientists conducted a prospective, 3 group, matched, double-blind, randomized controlled study with repeated measures of 1RM, local muscular endurance (LME), and magnetic resonance imaging before, during (after familiarization) and after their 8-week study.

Their subjects, apparently healthy 18- to 25-year-old men were (1) not vegetarian, had not (2) ingested any ergogenic supplement or anabolic steroids for the 6 months prior to the start of study, had not (3) ingested any medication that could affect muscle growth or the ability to train intensely during the study, were not (4) involved in the practice of systematized physical activity more than 2 days per week, for the 6 months prior to the start of study, and had to (5-6) have a detailed description of their lifestyle and daily food intake, and medical approval for the practice of physical exercise. Overall, 27 mean with a mean age of 20.6 years a height of 174.8 cm and a mean body mass of 72.7 kg met these inclusion criteria and volunteered to participate in a resistance training program the scientists summarize as follows:
Figure 1: Training session design. The numbers in the boxes indicate the exercise intensity (% of 1RM | Aguiar. 2015).
"Both the TR and PE groups trained under the same training regime (2 days week−1; 3 sets of 8–12 repetitions at 75 % of 1RM, with 1 min rest between sets) during an 8-week RT program designed to promote muscle hypertrophy (Ameri can College of Sports Medicine 2009).

The only [albeit highly significant] difference in the training protocol was that the PE group performed an additional set of exhaustive exercise immediately (30 s) before each training session [i.e. the pre-exhaustion]" (see Figure 1 | Aguiar. 2015).
Unfortunately, the only exercise the subjects didwas a bilateral knee extension in a seated position using a commercial knee extensor machine (Bad Boy Gymequipment, São Paulo, Brazil), with a range of motion of 90°–30° of knee flexion (0° = full knee extension), and the velocity/cadence of muscle action was 30 repetitions per minute (1 s concentric: 1 s eccentric | controlled with a metronome).
Beware! The "one-exercise only" protocol in the study at hand may allow for an increased standardization, but it certainly reduces the real-world significance of the results. It is after all well possible that (a) body parts other than the "quads" (leg muscles) react differently to pre-exhaustion (you know legs have to be hammered), that (b) the addition of pre-exhaustion sets to each and every exercise will eventually have you outtrain your recovery abilities, or that (c) the mere increase in volume made all the difference.
Each training session began with a specific warm-up exercise (1 set of 12 repetitions with a self selected load) for the quadriceps muscle. For the additional set of exhaustive exercise, the subjects were instructed to perform as many repetitions as possible at 20 % of 1RM until failure. As the authors point out, they "used a light load of 20 % of 1RM during the prior exhaustive exercise because previous studies reported that training to failure at a relatively low intensity (up to 30 % of 1RM) primarily recruits slow-twitch motor units (American College of Sports Medicine 2009;
Sale 1987)" (Aguiar. 2015)
Figure 2: Graphical illustration of the study design (Aguiar. 2015)
The idea was thus to induce the fatigue/exhaustion of the type I fibers before the high-intensity RT training in order to allow for an overall increased recruitement of the more growth-prone fast-twitch fibers. To ensure continuous progression, the sessions which were performed between 7 and 9pm were supervised and the training load was adjusted every 15 days according to a 1RM test.
Figure 3: Changes in load at 75% 1RM (similar advantages were seen for the 1RM) and cross-sectional area (=muscle size) of the vastus lateralis (VL), medialis (VM), intermedius (VI) and rectus femoris (Aguiar. 2015).
This practice lead to significant results in both the regular (TR) and the pre-exhaustion (PE) arm of the study compared to control (CO) - albeit with likewise significant advantages in terms of strength and size when comparing the regular to the pre-exhaustion group (see Figure 3).
What to previous stu- dies say? As I pointed out before, there is little research on the effects of commonly used intensity techniques like pre-exhaustion. What we do know, however, is that the "increased activity hypothesis" was refuted for leg extensions before leg presses (Augustsson. 2003), for flys before bench presses (Gentil. 2007; Brennecke. 2009) in previous studies. Re- sults that put another "?" behind the generalizability of the results of the study at hand. If pre-exhaustion works, its benefits are thus probably achieved despite a lack of in- creased muscle activity. 
Overall, there is thus little doubt that in this specific scenario the use of low-load pre-exhaustion techniques to exhaust the slow twitch fibers and maximize the recruitement of fast twitch fibers on the subsequent set is an effective means to increase both the strength and size gains of healthy, but not resistance trained subjects.
The subjects the researchers selected are yet not the only thing that makes the application of the results to real world scenarios difficult. As I pointed out in the red box further up in this article, it is is for example questionable whether the same benefits would be observed with a realistic training protocol. Furthermore, the fact that there were no significant changes in dietary intake over the course of the study is good, but a tight dietary control as it would have been possible in a dietary ward, only would have been better. Overall, I am thus still waiting for the 12-week resistance training study comparing pre-exhaustion on maybe the three major moves (squats, bench presses, pull ups) as part of a regular 3-day split in a scenario with a tight dietary control and the use of the standard supplements creatine and whey protein - in short: A study that emulates the real world of the averagy gymbro | Comment on Facebook!
  • Aguiar, Andreo Fernando, et al. "A single set of exhaustive exercise before resistance training improves muscular performance in young men." European journal of applied physiology (2015): 1-11.
  • Augustsson, Jepser, et al. "Effect of pre-exhaustion exercise on lower-extremity muscle activation during a leg press exercise." The Journal of Strength & Conditioning Research 17.2 (2003): 411-416. 
  • Brennecke, Allan, et al. "Neuromuscular activity during bench press exercise performed with and without the preexhaustion method." The Journal of Strength & Conditioning Research 23.7 (2009): 1933-1940. 
  • Gentil, Paulo, et al. "Effects of exercise order on upper-body muscle activation and exercise performance." The Journal of Strength & Conditioning Research 21.4 (2007): 1082-1086.
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