Breakdown aka Drop-Sets, Another Very Popular Advanced Training Technique W/Out Sign. Adaptational Advantages?!

"There are some crossovers between size training and strength training, and using drop-sets and ladder sets will definitely give some benefit ...," this is what you can read on the Internet, but is that true?

In view of the fact that resistance training (RT) leading to momentary muscular failure (MMF) has been evidenced as producing significantly greater muscular strength and hypertrophic adaptations when compared with RT not performed to MMF in various studies (Fisher. 2011 & 13), the assumption that techniques that promote the occurrence of MMF and the subsequent increased recruitment of motor units (MUs) and muscle fibers (Henneman’s size principle | Carpinelli. 2008; Jungblut. 2009) would produce increased muscular strength and size gains is only logical.

In spite of the existing evidence that training to MMF seems to be important for optimizing adaptations, the use of advanced RT techniques that allow a trainee to potentially train beyond failure, has yielded worse than 'mixed' results.
The latter goes for techniques, such as rest-pause (Giessing. 2014) and pre-exhaustion (Fisher. 2015), as well as using supra-physiological loads - all of them didn't show the benefits scientists had hoped for based on their ability to train to full or eve past MMF.

In a recent study, Fisher et al. did now investigate another commonly used intensity / advanced training tequnite: breakdown (BD) aka  drop sets o descending (Ogborn. 2014; Ratamess. 2009).

"Breakdown sets require the performance of a set to MMF with a given load before immediately reducing the load and continuing repetitions to subsequent MMF. As such, this technique can allow MMF to be achieved in addition to potentially inducing greater fatigue-related stimuli. It is thought that this might maximize recruitment of both type II and type I MUs through use of both heavier and lighter loads thus allowing the combination of high muscular tension and inducing greater MU fatigue, metabolic stress, and ischemia because of extended time under tension" (Fisher. 2016).

In said study, the authors expected that reducing the load from set to set would allow those muscle fibers that have not reached a state of complete fatigue with higher loads to be eventually recruitment, as well. The expected consequence obviously is an augmentation of the subjects' adaptive response to exercise, one of which we have little scientific evidence, though:
"To date, there are few empirical research studies that have considered the use of BD training. Keogh et al. (24) and Goto et al. (2003) considered the acute effects of BD training on muscle activation and hormonal response, respectively. However, neither study provides evidence toward chronic adaptations. Goto et al. reported greater increases in growth hormone (GH) after the BD training protocol (sets of knee extension at 90% 1RM followed by a set at 50% 1RM) compared with a traditional RT protocol (sets of knee extension at 90% 1RM)" (Fisher. 2016).
Since Keogh et al. (24) used a variation of BD training whereby participants only performed a single repetition at a near-maximal load (95% 1RM) or starting with the 1RM as it was done in the Berger and Hardage study before reducing the load for each of 5 consecutive repetitions, the significance of their results for anyone doing "regular" drop sets / BD sets.

Figure 1: Strength and size gains with regular training (HS) and regular training plus a single set of low-intensity high rep RT after 5 high intensity, low rep sets (Goto. 2004).

A more realistic study was conducted by Goto et al. in 2004. In said study, the participants performed 6 weeks of an identical resistance exercise protocol and were then divided into either BD or traditional training groups. The traditional training group performed 5 sets of knee extension and leg press exercise 2 times per week at 90% 1RM with 3 minutes rest between exercise sets. The BD
training group performed the same protocol with an additional set performed 30 seconds after the fifth sets using 50% 1RM, where all sets in both groups were continued to a point of MMF.

The authors reported significantly greater results for leg press 1RM and maximal isokinetic torque (300 degree per second) and muscular endurance (repetitions to MMF at 30% of maximal voluntary contraction [MVC]) for the knee extension for the BD protocol compared with the traditional protocol.
However, as Fisher et al. point out, the "authors reported that the BD group showed greater increases in muscle cross-sectional area (CSA) of the thigh compared with the traditional group; however, this did not reach significance (p , 0.08)" (Fisher. 2016) - a non-significant advantage with a training protocol with higher volume? That's not exactly convincing, right?

The new study - What does it add to the existing research?

Therefore, Fisher et al. did another study with a randomized controlled trial design was adopted, with 3 experimental groups included. The effects of 3 RT interventions were examined in trained participants upon muscular performance and body composition.

Figure 2: Consort diagram showing how the study was designed (Fisher. 2016)

Participants were required to have had at least 6 months of RT experience (single-set training to MMF for multiple exercises including most major muscle groups, >2 times per week) and no medical condition for which RT is contraindicated to participate. Participants were then randomized using a computer randomization program to 1 of 3 groups: regular BD aka drop set training (n = 11), heavy-load breakdown (HLBD, n = 14), and  a control (CON, n = 11) group.
Participants were asked to refrain from any exercise away from the supervised sessions. Body composition was estimated using air displacement plethysmography (Bod Pod GS; Cosmed, Chicago, IL, USA) before and after working out twice per week for 12 weeks according to a protocol, Fisher et al. describe as follows:

"Each exercise was performed for one set (+ breakdown set in the BD group) per training session at a 2:4 repetition duration until MMF (i.e., when they reached a point of concentric failure during a repetition) to control for intensity of effort between groups. All participants performed 2 exercise sessions per week. The first of these, workout “A,” consisted of chest press, leg press, pull-down (MedX) overhead press, adductor, abductor (Nautilus Evo, Vancouver, WA, USA), abdominal flexion (MedX Core Ab Isolator), and lumbar extension (Roman chair using bodyweight or manual resistance; Hammer Strength, Rosemount, IL, USA). The second session, workout “B,” consisted of pecfly, pullover (Nautilus Evo), leg extension (MedX), dip, biceps curl (Nautilus Evo), seated calf raise (Hammer Strength), leg curl, and core torso rotation (MedX) resistance machines" (Fisher. 2016).

As usual, the weights were increased by 5%, once participants were able to perform more than 12 repetitions before achieving MMF.  The breakdown / dropsets were used for the chest press, leg press, and pulldown exercises in workout A only (e.g., the exercises that were tested). All other exercises were performed to MMF with a load permitting 8–12 repetitions.

• BD group: For the chest press, leg press, and pull-down exercises, the BD group performed a single set of 8–12 repetitions to MMF and immediately reduced the load by ~30% and then continued performing repetitions to MMF. 
• HLBD group: Using the same 3 exercises, the HLBD group used a heavier load permitting only ~4 repetitions; upon reaching MMF, they decreased the load by ~20% and continued performing repetitions to MMF and then repeated the BD reducing the load by a further 20% and performing repetitions to MMF. 
• CON group: Subjects in the control group performed all exercises for a single set of 8–12 repetitions to MMF with no BD. 

As Fisher et al. point out, the "group protocols were chosen to allow parity between training load (the BD and CON groups both used the same relative load to begin; permitting 8–12 repetitions) and repetition volume (the HLBD and CON groups both performed a total of ~8 to 12 repetitions)" (Fisher. 2016)... and guess what: With identical load and repetition volume, the scientists found "no significant between-group [pre vs. post] differences" (Fisher. 2016) for change in absolute muscular
endurance for chest press, leg press, or pull-down exercises or for body composition changes.

Figure 3: Looking at the error bars will suffice to tell that there was no significant inter-group difference (Fisher. 2016).

In line with that, the effect sizes for absolute muscular endurance changes were large for all groups and exercises (0.86–2.74) - again, whithout significant inter-group differences.
References:

• Fisher, James, et al. "Evidence-based resistance training recommendations." Med Sport 15.3 (2011): 147-162.
• Fisher, James, James Steele, and Dave Smith. "Evidence-based resistance training recommendations for muscular hypertrophy." Med Sport 17.4 (2013): 217-235.
• Fisher, James Peter, et al. "The effects of pre-exhaustion, exercise order, and rest intervals in a full-body resistance training intervention." Applied Physiology, Nutrition, and Metabolism 39.11 (2014): 1265-1270.
• Fisher, James Peter, et al. "The effects of breakdown set resistance training on muscular performance and body." (2015).
• Giessing, Jürgen, et al. "The effects of low volume resistance training with and without advanced techniques in trained participants." J Sports Med Phys Fitness. Epub (2014).
• Goto, Kazushige, et al. "Muscular adaptations to combinations of high-and low-intensity resistance exercises." The Journal of Strength & Conditioning Research 18.4 (2004): 730-737.
• Ogborn, Dan, and Brad J. Schoenfeld. "The role of fiber types in muscle hypertrophy: Implications for loading strategies." Strength & Conditioning Journal 36.2 (2014): 20-25.
• Ratamess, N. A., et al. "Progression models in resistance training for healthy adults [ACSM position stand]." Med Sci Sports Exerc 41.3 (2009): 687-708.
• Sandee, Jungblut. "The correct interpretation of the size principle and it’s practical application to resistance training." Med Sport 13 (2009): 203-209.