Low vs. High Load Resistance Training - Yes, You Can Gain Muscle W/ "Low" Loads - Non-Significantly More Even!

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It turns out, the biceps may even benefit from higher rep, lower weight training.

You probably remember my Facebook post about Brad Schoenfeld's then unpublished study which proves that you can gain muscle using low(er) weights, as well. Now, that the study has eventually been published, it would appear to be about time to take a closer look at the procedure and results in order to determine how relevant, the finding Schoenfeld, Peterson, Ogborn, Contreras and Sommez present in their not yet printed, but peer-reviewed and accepted paper in the Journal of Strength and Conditioning Research.

The purpose of the study, and that should be obvious considering what I already gave away, was to compare the effect of low- versus high-load resistance training (RT) on muscular adaptations in well-trained subjects.
Schoenfeld et al. recruited eighteen young men who were - important fact! - "experienced in RT". More specifically, ...

"[s]ubjects were between the ages of 18-35, did not have any existing musculoskeletal disorders, were free from consumption of anabolic steroids or any other illegal agents known to increase muscle size for the previous year, and were experienced lifters (i.e., defined as consistently lifting weights at least 3 times per week for a minimum of 1 year, and regularly performing the bench press and squat). The range of lifting experience for all subjects was between 1.5 and 9 years of consistent training" (Schoenfeld. 2015).

The subjects were matched according to baseline strength, and then randomly assigned to 1 of 2
experimental groups:

• a low-load + high rep resistance training routine (LL) where 25-35 repetitions were performed per set per exercise (n = 9), or
• a high-load RT + normal rep routine (HL) where 8-12 repetitions were performed per set per exercise (n = 9). 

During each session, subjects in both groups performed 3 sets of 7 different exercises representing all major muscles. Training was carried out 3 times per week on non-consecutive days, for 8 total weeks (not other high intensity exercise was allowed during the study period;; dietary intake was monitored and didn't show sign. inter-group differences). The exercises performed were: flat barbell press, barbell military press, wide grip lat pulldown, seated cable row, barbell back squat, machine leg press, and machine leg extension. As Schoenfeld et al. point out, the "exercises were chosen based on their common inclusion in bodybuilding- and strength-type RT programs" (Schoenfeld. 2015).
"To facilitate recovery", the researchers provided the subjects with a supplement on training days containing 24g protein and 1g carbohydrate (Iso100 Hydrolyzed Whey Protein Isolate, Dymatize Nutrition, Farmers Branch, TX) which was consumed within one hour post-exercise, as this time frame has been purported to help potentiate increases in muscle protein synthesis after the workouts (cf. Aragon. 2013).

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Figure 1: Overview of all relevant study results. Only the changes in squat strength and strength endurance as measure by 50% bench presses were statistical significant, there was a trend for greater increases in 1RM BP (Schoenfeld. 2015)

As the data in Figure 1  tells you, both resistance training protocols yielded significant increases in biceps and triceps size. For biceps, the high rep training had a measurable, but non-significant edge producing 8.6% vs. 5.3% increases in biceps size (remember how people train their biceps, that's often ballistic, i.e. they are throwing high weights around, so maybe the benefits are simply a result of improved form).

For the triceps, the quadriceps (9.5% vs. 9.3%) and the biceps' antagonist, the triceps (5.2% vs. 6.0%) the differences were marginal and likewise non-significant. Now, it would be revealing, but boring if the results of high rep + low load and low rep + high load training were identical, right? Well, luckily, Schoenfeld et al. did find differences, as well. More specifically, they observed that the

"[i]mprovements in back squat strength were significantly greater for HL compared to LL (19.6 vs. 8.8%, respectively) and there was a trend for greater increases in 1RM bench press (6.5 vs. 2.0%, respectively)" (Schoenfeld. 2015).

In addition, and not much to your surprise, I guess, the upper body muscle endurance (assessed by the bench press at 50% 1RM to failure) improved to a greater extent in the low load (LL) compared to high load (HL) group (16.6% vs. -1.2%, respectively).
References:

• Aragon, Alan Albert, and Brad Jon Schoenfeld. "Nutrient timing revisited: is there a post-exercise anabolic window." J Int Soc Sports Nutr 10.1 (2013): 5.
• Kraemer, William J., and Nicholas A. Ratamess. "Fundamentals of resistance training: progression and exercise prescription." Medicine and science in sports and exercise 36.4 (2004): 674-688.
• Schoenfeld, et al. "Effects of Low- Versus High-Load Resistance Training on Muscle Strength and Hypertrophy in Well-Trained Men." Journal of Strength and Conditioning Research Publish Ahead of Print. DOI: 10.1519/JSC.0000000000000958